Master class I with David Quéré

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Master class I with David Quéré
Wetting and roughness
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Two hundreds years ago, Thomas Young understood how the solid/liquid contact is dictated by surface forces. Our plan is to discuss how the solid roughness modifies (quite dramatically) this law. Roughness can be either accidental, or set at a surface with micro-machined extures, which decides the resulting properties: super-hydrophilicity, water repellency, slip, anti-fogging properties, etc. We present recent developments in this lively field of surface science.
Keywords Surface Physics
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so it's quality time To start so thank you for coming I want to pressure for me to teach doings in light of the familiar misled back and I'll give you a chain of and so we sound like Maple if we will gain of pursuing useful clock because if you it's too boring you see that its policy and is you have and that at some point and also you you see that's what I would like to discuss tonight is that as I
said initially Whittingham of menace and that's what I was told to stop the Morris from scratch I about your backgrounds may be very different and so the 1st part is analysts on lasts Al embarrassingly even simple it's clearly symbolizing wedding but it's very useful for the rest of the of the talks over the 1st half an hour and the fact that most of you are completely aware of all that I hope that the of 75 per cent which which come after there will be with some aspects at this new fleet so if I had to say something very simple and originality I would say that letting phenomenon I had been steady fall very long because values for it's useful to understand how 30 quid behaves close and so people from companies they only started to think out that have elected is quite new that is and understanding although and the fact that people realize that if you add the toughness which is their natural because most studied art but also to date it's possible to induce a special softness and it's mostly what we are going to discuss then waiting might become even more exciting in the sense that you can generate using a imitates touches pictures the properties of which you could not without researchers so it's clearly and that's exactly what was when because it is somewhat less than your solution it's clearly trying to In use a new public is using it as something on this and so I will try to hold that exemplars of a famous about that but I am trying to make a gain of lists exciting problems and some of them are I think the new in the sense that they have been very police that it so I would be of course they're interested in you know the actions by the way ideas that most of you work the is just somehow related to what are going to discuss tonight and I will be very happy to discuss ways of resuming you if you have the possibility during their meeting here so the outline is as follows a visionary .period but you have the heartland from you so 1st part as simple reviews and waiting it is a state of of the art I would say in the late eighties all beginning of the 90's uh which are the classical waiting you want and then the parts 1 is about you behind affiliate states so the fact that was left as you can induce enhancement of quite a few city which was discussed but so not that much unnecessary and so it's interesting to see the kind of situations that you can generate with hydrophobicity then zoo
opposite case the case when you have both toughness and hydrophobicity and followed by far the most famous spot people who are very excited about the possibility of generating what we like to call fact he'll drops the fact that drops can be like produce on unsullied and so as a consequence of very very easily evacuated from the sentence the main asphalt it is a consequence of the film 1 it's what I like to call hydrodynamics without contact find that when you generate a very poor letting you when you are very close to a drying transition something like that then you loser contact between the solid than the agreed and so is Queens behaved very very differently From what I used to and this is a field which is I think in opening the understands that the once some ideas are here but there is a lot to do in this field so it's mainly something where are the future Is that at my opinion in this I must add that if I had to this easy axis of time of course tonight but I would say also that this is the x axis of excitement in principle to uh uh the longer you stay here was more excited might be because I will be at ease because I think that these voters are more and more interested so what did the wedding of classical with the solar variability and Medellin definition waiting is what's happening when you have free phases which meet each other and that I would say that the most common case about that is equipment which is coming on a solid year water on best state with around the air this is where much of this is the most common situation of course you can imagine many situations of this kind liquid liquid air so he'd quit agreed and even in some cases can lead partners and so on and so have I don't know of sodium vapor the itself and so when we look at the final object that we have but this would at 2 fingers the first one in the shape and the shape and the scale of rock which is bit quick skating is obviously a portion of the sphere portion of 2nd disk so we have a spherical caps and of course people understood very early about 2 centuries ago why we had this very true mathematical but of course surrogate gap is not the shape it's a family of shapes and the southern part of it is that you have a naturally once you said it's a it's a silicon cap is the size of the contact between the Sweden's Annika and people who are interested in applications generally op interested in responded because of this uh quantities logic means that the McQueen lights Soviet and this can be beneficial .period of shifting of the paint on a wall in warm feelings of pain to spread but in some cases you to avoid his contacts in particular industry agreed has some candy collection and this only think about water on concrete point of this is nearly all inland water on Lost and so there are cases where you want to maximize this contact cases where you want to minimize so these are the 2 quantities to be fun so here I said I will be embarrassingly simple and so this is 1 point where I'm sorry about that but the 1st thing is the shape and the shape is related to the presence of so fast tension and this a face-off of any quick and listen as you know which was more misunderstood by different people but I would say that the very very brilliant paper on that is due to the Tomas known papers page of the paper is on the cohesion of fluids Tomasson was interested to understand why forwards are heavier and he understood that this is related to some of that action between the molecules which means that when accused closer face have higher energy which mean that the still face it said has especially in energy which is proportional to the number of 20 Ecuador's face that is to the surface area of my black and the constant the proportionality is causes of ascension of this he quit and of course it reflects directly the cohesion of my foot more cohesive related to larger quantity down and this was under surveillance it's very funny to say that in the very famous book by good at the beginning of the 19th century 2 years after the paper by Tomas Young good to in elective affinities has a very long time and I laugh about that and he says that of course mentally ill as he did in Desert highest of essential that idea of cohesion and water and it said higher cohesion that all units of the scale of the quake and skate off yet and so as a consequence the system if it so the form of a system which is the case for liquid vapor or equally agreed I can choose the surface area which minimizes this quantity and so this is the reason why you observed Sago shapes this is on all only fools of pools of liquid vapor bound however of course you can define this type of quality for any face each died of a composite Wintershall faces you have a corresponding amount to be between serene and equally sorry and vapor and within the and unwitting phenomenon is an interesting it becomes that free of these parameters because you have 3 phases and 2 of 3 kinds of bond ideas which are really unite previous example asserted liquid sodium vapor and it could be as of now what we have to understand is so contact between the city and agreement because we know the shape and golf course we know generally the volume of between between deposited on a given solid it's equivalent to I think in terms of contacting this once again is due to Thomastown International the 1st to calculate the value of this contacting he not least militarily about the conduct and only the property which is leading local repeats it does not depend on the size of the system and so this the experiment where you take the same Presti who put the same equipment you various volume of liquid and as you can see the shape of course depends on the will you when you have knowledge you the shape is threatened by guard the rules vocal shape because of its acts and makes a so liquid flat but the comeback and in the 3 cases is the same so if it's fixed at the very very local scale and there are many discussions about that how well over what kind of scary should be defined and if we want the
very smallest gain we see observes the same macroscopic combatants on it's not a something that I shall address tonight but it's itself cause to it's very very interesting questions which is interesting ecstatically but it's also interesting and dynamic any of course if you start to move of course this question of stays out absolutely crucial the way this and is calculated using Jessica so In case you never saw that I do it quick so this is not something but acquitted is here and it makes a full and I focused just closer contact on the compact I'm is very special place where you have the free phases liquid they personally and it's a place where the contact angle is somehow decided and the way to calculate also ways but 1 which is very elegant I think consist of thinking of the success seems a little the Giants at the drop makes when he contacted insulated and and you look at the at the end of the story when you reach the final at William Compaq angle and so you consider that last job and the job is made by the quantity which is years X and you calculates the corresponding chant of suppressing energy using the formula as a formula that each time you but sufficient corresponding most of us in and so the panel corresponding valuation of suppressing here there is written going at length of the contract line 4 per cent in history and 1st you create suddenly quit in the face you surprise soaring vapor interface you knew that on the surface area per unit lines which is just the X and of course has dropped spreads you create new relying solely on creators your face here which is fiercely the segment and so you have to add here galvanized the liquid vapor the ascension the X "quotation mark and of course have the drop stops when it finds its equally which means DE is 0 0 0 from which you find this a for Compaq formula which is that of course I am generally is a difference between the 2 solid so personages divided by those of us in any of the followers of and astonished be it must because it's certain the dimension is quality which has been whiz uh quantities which have dimensions and the side assuring physics it means that you have contact with the outside of the ballistic forces and hearing the case the force which is under the the numerator is the 1 which pies on much of you'll drop and of course the denominator betrays the fact that when the drop is by being itself ascension it would vapor exists it is fighting for this force of course we're going use this so it's very natural to find a solution and when you look at all and in the paper after my strong governor equation of of young you have no nothing like that of course this is a modern way of thinking you have a kind of fella presentation which I think is this 1 and it's 1 of those sudden it's not easy to use generally but it's only it's food is no calculation that I cannot resist any new executives West proposed by Damascus so of course you have to think of the compact and I would like to say the compact line is a place where each interface stops is advisable if I look at the Sony vapor interface it stops here because then it becomes something else which is a solid liquid and he failed at a summit between interface it stops here and immigrant stops here so very there is something very particular to compact line which is the fact that at this point interface stopped which means that at this point forces are acting in such a way look at this energy in such a way but each of these so if your face .period tends to minimize the corresponding suppressing their Shh but nobody should look at the city and it was vapor defaced it stand intends to draw the line the walls of the right here because if it does so you suppress your favorite wintering and so this is the way this fall because of cost when you see the dimension of this quality you see this as an energy 33 reality .period Williams 13 plants and so these false tends to act in the direction of course suddenly agreed interface act in the opposite direction and equally poor interface acts by use of face which is the sole right and so when you say about is that the good-neighborly and stops it finds its optimum state it means that the users these forces have to balance of course should manage these forces on the horizontal lines you immediately recover Young's equation it's a very very arrogant way of thinking that there it's very difficult to use when you have a complex of face and you get very easily lost in this fall's I me in this force of balances but I think it's it's nice to see to it that his once the way he should project on the vertical direction it seems that something that friend happens there is no 1 can know no no force opposing this 1 and so people felt a about that in the in the nineties and said and realize that service forces existing betoken falls and slightly pinches a solid and so if you look carefully at Sony which have very low young motorists something like that the surface of you will for the book on which it was at the drop of water you can see small deformations which related to the fact that none of these vertical force which is active and which is resisted by the elasticity of the of the Saudi so In this equation which are extremely interesting both a conceptually and obligations and 1 is the limit of complete with the fact that in some cases you take a city in the same breath stink you put adequate notice of water it's so it's it's annoying and you there was a dual drops and they spiders there is a very nice and the maker of Finland the thickness of his fame of course can be questioned the dynamics of spending can be also discussed how many discussions about budget before the question is how can we this happened and if we fail
on I think something like that of course is feeling if it is by nite by text and policy to invade the study is is what we saw now if I think about Young's construction it's very clear that at this point which is the point at which the interfaces stopped the Nothing deck a contact climate it's it's OK to termination point of interfaces I have my previous forces rotting cited on political my films they flat and lies that if the sodium vapor fools is larger than the sun Of the tools of forces then indeed Queen the to spread so this is a natural condition for achieving concrete spending and when I come back to this equation I realized that it means that administrator must be larger than the and of course this makes sense I cannot define anymore because sign in these quantities louder than it so it's very well connected to Young's equation appealing only for these quantities they can be anything and so there might be a possibility said that these quantities lover and this 1 so it means that the liquid is pending on the site so it means 1 of another it must have a very high surpassing energy which is a case for war the loss when you make it and when you go to nonunion factory of glass when you look at the glass is a fascinating and take a drop of water you put global Ford and Larson very nice something that you never observed of windowpanes listening that the faced was a very high in energy His medical people who want to buy anything because anything is that energy of the sun and so after typically 5 minutes it's into shortening nowhere your your your your glasses not with the anymore bye bye bye bye bye what but I would guess from guy Tiger in the village in Italy is assuming the very high energy should be weighted by boys anything except in this anything as it has itself a very high surface Of course if you think of Mecca the Mercury visits by then on on any sunny and the reason is that the sport is extremely laugh American the Soviets cannot be satisfied Of course if you have any questions you you please contact this time said at a news site in different fashions and this this way of thinking was proposed by mahogany and Italian physicist in the during 19th century he said well we have a solid which is dry and possibly when the liquid is coming this so they can become wet and this means but change the nature of this office it was a surface energy of dry in and buried area to surface energy is done not selling vapor and 1 of the if of fame has spread on Missoni and I have no 2 interfaces with corresponding personages and of course I find the same as the same criteria in this energy the smaller than this 1 it means that at some of the 2 sides and acquitted on the Syrian and of course I find sectors in part criterion which is "quotation mark Teton all-German units there is another way to approach this interesting unit of computer within which consist of coming back to Young's folded and this is to prepare something with the late if is holding up I imagine that my mom my solution is such that it looks into the legs of liquid but I'm going to put on this earth it's liquid life so I knew that the fall love and I find again last Sunday so could vapor OK -minus Galilee quickly quick which is nothing it has get that would be permissible issue which is here tends to want 1 and so this means that the anger becomes you and its ability to result in a sense the fact that if my sword is that we like and if I come with the same degree Of course the liquid that we spend on this liquid if you put a drop of water on the border with what but it means that if I find traits to treat my solely in such a way that it becomes he liquid like I will going this interesting action without harm without having something not necessarily Khandaker so this is of course a way to say a toughness lights had to make a solid liquid light as we see later the all the committees of all the interest how to make drops very cycle like proves how to reach very high compact mangoes while a Canada it's not possible and they were long long debates in the 60's and I should "quotation mark the name of this man "quotation mark quite a famous paper whose title was at the need for the contact and then onto it was an anti-illegal vapor where do you get the possible chemistry of the surface of a solid he made extrapolations he was a master at that and he found that the people of Britain it would be input into it would be impossible to find ways of water which is the the most natural liquid and solids on which to contact and is larger than 100 degrees and so he should develop very sophisticated uh truly native molecules to put the new signings a very sophisticated waxes you cannot rule the on the obviously and I think this is true of destiny :colon on effects lead uh which for which you expect this relationship to be world late and it is true that the the largest compact and around not to back the largest 1 should 180 degrees and are succeeding reason Thomas so they needed some of what some space to feed here again if you come back to Young's home you realize that there might be a possibility to will much much further if you make your solid vaporize now instead of liquid so if you find a trick To make that the city that somehow somebody's paper there then you look at the full of his gun which is 0 my nose down or demise and so of course makes minus 1 and so it means that if also vapor like the Compaq and there should go to 182 and so what I just said before is fight that Kinnock and nobody knows how to make the sodium vapor lights but we see that the wizard affectionately as you probably know it's possible to approach this year it's because it's possible to trap air and so this is a way to make Of course vapor lights in the city this fear was that the rebels of affair it is nearly 1 unit where this is completely satisfied which is a unit of flight and fast so it's a very special 1 for that it's a very interesting 1 and take a something and you during this early in at the time departure which is much larger than the boiling point of the nuclear sold to become a steel or copper at the departure effectively 100 degrees and you deposit a drop of water on this sunny and you see a perfect unwittingly you see something even better which was
discovered very probable by this German physician visible he put condoms behind and he could see the July passing below drop and so he understood that these jobs are not contacting animals associates will indeed you gonna connecting the city's contact and then there's no contact they are dictating on of vapor and they the 15 consumption because the city so hot it's funny because when you look at these drops there nobody inside is remarkable the studies um then agreed with the ease and the Boeing .period but you do not observe avoiding because there is no possibility of vacation because there is no he also noted that the scale of 1 unit which is here the thickness of the paper thin is typically the thickness of hair solos 109 connectors so it is visible with the naked eye we can understand that nite and lost within this very careful experiments could indeed clearly I understand the origin of these phenomena and as you can see this phenomenon is captured by Young's equation because it's a case where the city became a vapor in which in which case we find sign is administered and of course this is for people interested in this field is the other teammates gold we would like this is a guy who would like to approach the situation and the question is if we approach it as do we get properties which are comparable to the properties of flight and was dropped plumbing so drops of liquid nitrogen on the floor now so quick now so life and so it's interesting to do just try to guess if we are not exactly at 180 degrees but get sick at 170 heat extremely different toys at compiled and this is a question which is I think very interesting because top-quality many answers to these questions we're going back to completely so bizarre that I would say is overdue off off off off with and I would like to add a few compliments which I think you know quite well which is a van but on the field who faces a real meaning that 2 phases where you find many defects this can't afford lower generally not debate exactly almost discussed carefully as pulled by this very naive experiment where another Sony and and it was a job drops this is the first one that you needed was a you make 1 which is slightly larger this is my son-in-law and it's in both cases this stick to the slightly In both of these drops in alive despite a stroke and so it means as a compact and it is not unique because if it were you need if you had 1 guaranteed job he and here Of course and drop shouldn't France's slope division being that you do not affect any of the surface energy when you when you follows a stroke and you lower your limitations it Of course you make develop knowledge a at escaped when hundreds forms in it then of course got becomes larger events of US forces wasn't so you observe they naturally was something that we all know from windowpanes again when it's raining Mississippi the ones are stacked the big ones go go go quite strict if you take a picture of the use of study drops missing at Indian velvety a symmetry and there is large angle of the frontistes willing edge and you can define the difference between bovine goes than that up which can be there are a lot in this case 90 degrees 30 degrees of differences to begin 16 degrees so it means that if I had to define the compact and therefore drop I would say that while it's 60 pressed minus 30 something so it's not a smaller evaluation it's not saying while this is merely satisfied in this case is far from the scene and some people were extremely interested in the origin of this quantity the consequences of the existence of the so-called histories of the compact under which is a phenomenon which is here and there decorating possibly this morning and so well this was more so consequences until Tuesday once you understand that these jobs site symmetry you don't care about stick because you have a very famous role Young's rose famous and the surrounding low in interview nighties that breaststroke the fact that when you have an interface which is curved and crosses interface jump of questions and so here the can is not homogeneous is a constant which means that the pressures that comes when you cross interface here is the largest drop of pressure because the country's high when crossing the face hearings more job of pressure so there is a pleasure false which is acting that way and so of course this is the reason why the drop steaks this fall's balances got and so when you say that again SoHo evaluate His faltered and calculated and so you can be in the kind of things that harm all now the mobility of for you fix gonna feel sorry in this case it's a vertical slits of maximum annual if it a sizable drop size of 180 mm which is devoted to become a raindrop and you look a forgiven debt that is done which is somehow characteristic of history and uniquely and demeaning Contact Energy down you look at the possibility of satisfying all notes the balance between the sticking falls and on and what you find is something where the majority investment jollity of is that they are on the occupied by the sticking face so you dropped states and so this is of course a very common observation and if I have come back and those between the 2 20 and 100 degrees and tell them to be the venues if I want my my dropped to 2 2 2 2 slide of 2 to follow so the slope which in the station is 90 degrees maximum 1 contact and is that it is then that thought was this more of an few so it means that I have to enable the Sony which is absolutely perfect timidity and physical because of all the genes often that . is in the defects of the sort and so this is something which is mainly feasible but as I said for gloss after a few minutes there are some contaminants just coming into lose this idea so if you are interested in Soaring these questions particularly it's impossible to solve questioning if cannot achieve a solution was a permanent then that 2020 the solo but with later trick which is which said however I makes this Legion there is another solution which I think justifies the fact that so many Rogers said in should before Mitchell which is the fact that a lot something like 160 degrees of course is very independent and which was here the line which was very becomes more which
means that even if their database .period louche In procedures which is the drop from the mobile vandalism is very obvious when you calculate the stinking force you have to invigorate on the contour of the drop and so because in this region so becomes nearly spherical the company contact associated and so the force of intervention imminent and that it there is nothing to do so there is something very clear here which is that if we are able to make a comeback and in this small allegiance of the mobility should be much much higher than usual and so this is perhaps this is the 1st to expression but it's a pain of static monitored the fight but the drop starts to move but then but is much more interesting is abandoning mobility is fact that if it moves it would be much weaker than usual so suddenly uh uh uh paintings there's a there's a sticking so so so intrinsic dynamical properties that you can have a debate which we'll discuss it a bit development how 7 consequence of the existence of compact agonies that is this is so his evaluation of compact and is a so-called coffee stain effects something which was that is in the years 2000 by in particular by the Chicago Wolpe along the common the Whitten so they took pictures off a drop of coffee as available so it's a it's an experiment for the series EPG student because it's very very slow and sweet delivery when they had you take 1 picture per animal the life and work and then you make a movie about to and from the top and the beginning of course you see that it's darker at the center that had the benefit because of the shape of the drop so it means that you have more articles of coffee as a center None of the patients and if you look as a function of time and and its shape whether it's clear about our displacement of matter and at the end of gang of staying and it's something that you probably the observed it's very common and also which is very remarkable in this experiment this line moved it's becoming clear from the beginning to the end and of course if you is brawl were satisfying this equation so if you had a job like this and you end up a dropped it should make that the key to conduct account so the 1st the 1st effect which is there is related to the fact that you start was given them and because of the possibility of having his contact and inflexible in his letter that he up then you can use a line here and at the same time something is of course all clues which is a fact that matter the songs bolted from the center why but because close to the contact line interpolation becomes so some hope that the magic uh uh 8 states and engine which is was very small was a very high shield between 2 phase and will you and so you have to transport matter to feed these these these regions divergent of interpolation of this sport and so the solid is harmful to but because of possible the Soviet Union the Honda compact because kind of pushed and so all provides a compact and history escape because you beyond a few defect at the beginning but then have many in effect because you have all this particles that you put a contract line and so depending which was the quite strong at the beginning of the meeting becomes intense and so this is the reason why and Tunisian and completely flat Of course and interpretive flat the teeming speeding buys a contact if you don't do this very early briefly in this 1 now None of this is the 1st of these is the position of the weekend at the completion charm and all they also can be used that to be the velocity at which particles are transported and they could prove that it was In the argument was experiments where not here freeways about and you look and Spartacus under a microscope and you clearly see this you the transport of particles I don't want to contact this Of course this question of spinning are absolutely crucial if you want to go to understand the contact in the history of this evaluation of contact and if you think of a technical defect to other study which is flat but the chemistry changes at some point as the contact with the 2 . 1 here and do that to bear and of course at the border between the 2 regions the other possibility of having a flexible compact and any value between 2 . 1 injured at all in this macroscopic is example is very clear that microscopic defects can generate the situation of the compact and the indelible between these values can be as large as you not because its own independent vendors of two-to-one and Symphony music physical defect this is a physical defect wherever King ,comma engine for the political movements and it like this you don't see goal it's at the scale of it to when I committed but when you put 200 quid on its you always think that there are things he's always Ontonagon make a mistake if I dare say when the merger is a compact and because on the left you observe Quebec Canada which is to 1 on the right it's also 2 . 1 but on the stroke which is fine and so as you can guess when your contact 9 is going to take year you have any land between the the digital 1 agenda which is there With respect to the horizontal which is 5 minus-5 pressed to until recently also I'll be tallied knowledge for the body to fend off filling and even almost filling a glass of water we all know that when we feel less of waters of Hong Kong that ended in the 90 degrees at beginning 180 degrees and for a glass of water the top of a glass of water 5 0 because you have the solid worlds of glass which does that surprise you will and a 50 . 1 0 you see that at the top dying can be between 0 and 5 miners you will present rules which is exactly what we observed when we all feel a glass of water so all of that is labeled him because it says that while spinning it is something which will close on defects 1st thing I and something if we have many effects the line we find a way to accommodate these many defects and then the difficulty becomes a decade and many many people try to solve the question following question if I have a map of solid and I know the strength of the defects and what is that Compaq and instead which come from that there is no Ohioan answer the main effect of a single wanted to clear many defectors it remains remains in full for the movement not to let the diesel now few cases where people found solutions In particularly as a very famous 1 proposed by division in the late eighties but it corresponds to a case where the defects of the and a strong and it's quite far from so it's not it's not illegal to use the
services business but as you can see them while there and is no finding local connection between this idea or and the fact that we have been informed of that locally I always satisfied Michael and so it's something that we have to keep in mind the fact that this is competing local means that it is always scale where you must be aware and it's something which will be useful cited so this was a very long story become interdiction and I meant to do to discuss nobody's quite sure what part of chapter on defeat states so now I would like to challenge opinion the point of view so I was saying I consider it very ideal solid OK I have classical shows no I say Sony are so do also I have some defects and try to treat his defense the easy as I said that I would like to say something about justice that I would like to place on solely very well defined effects and to induce tried to induce new public so this is a picture we have a solid and we bicker later recently this summer at some structures at the game which is clearly about the size of the molecule but much smaller than the size of the drops which are covered with you think afraid of this persisted and women at cancel the standard to greater 10 likened the job of course possibility of changing the scale and it's something that we also discuss later I'm already and people from the Michael interconnects community uh announced how to be a very sophisticated such as of this time and so we see later examples which are indeed very beautiful so what could happen the people who support me only raise a question the 1st in a very convincing way where the people from the Cal compilation in Japan in the late 90 s and if I had to to say I what to what was the main contributions which decided that this figure will become very exciting for me there is absolutely no doubt that the papers by socialization she done on group are absolutely to be good what they did is a very simple experiment where took a solid and they that should be saluted and they compare the comeback and the on this only when it is flat so it must be something like a young contact angle and likely to tell and you take the same chemistry but should you change picture put the texture actually become something like that change and you was it's the same acquitted on the Soviet military detection before you were living is always on told the skaters to small and you merger of New England which is of course and from something at him up on compact and only got no executive detail here and what they did is to compare 2 bus stop and and the way they do that to take to findings of his time and to put the series of liquid and is so insurance if you take a series of equally varied and for each tee talent and measure dust and so it it means that they compare zone to people working as a function of the toughness of facilities and they find something which is on the fact that when you add some what's necessary generally you changed to begin contacting the ritual so they brought "quotation mark did dust start as a function of wasn't at all and if the toughness had no influence you would have to dust are equality down which is already that In the deadline is obeyed by 1 for .period what you find is that of the height the box was the height of the is this 1 "quotation mark is positive and is a "quotation mark is positively means that the Compaq primaries more than 90 degrees then you find that dust is always more so at the height of Phoenix only becomes more like a phoenix conversely if the . is now demanding to agrees you find that dust are much rather than too tough which is a hydrophobic so we focus is now in the height of the pot and of course we would like to understand what's going on here and Ugandan new accused and when I said he's got people while discussing what could be the other possibilities but generally it's reasonable to 7 . 3 possibilities with deposit of solely in illiquid did a great job somehow follows the accidents of the solution all right maybe could stand at the top of the solids or maybe he could at a need in the city so it could streak which could think all I am on the kind of media so I II start to invade his post it's a very special posting chemical because at the time the boss medium but however can treaties so started as a kind of cost and telling each case the blood is in contact with something which is very different in the 1st case it's in contact with Russell in the 2nd case to contact with tops of the solid and hear it's in contact with something which is of the field was the same liquid and of course you remember I told you when she makes it solely vapor all allied you have something that you expect them to the city's LIT it solid is equally like you expect something else under the sun in his bid to win like and so you can understand that using often Northwest indeed helps you to win this interesting so the man who developed the 1st and mother about that but it is quite famous his name and then there's did evaluation on this equation which is there that is the start of from his picture that's enough and not something that you will we must introduce at least 1 ballot which is the so-called roughness factor and the definition of factories a infinitely simpler when you look at the city the university anything special for you think the chauffeur story of these 2 ladies of this week the time to be set ranks but of also Heroes of History out there if you want to measure it you have to take into account is that he is mountains and to issue dividing the 1 the at and finding find them the which by definition is another immunity and this is going to have respect so it's now you have here also instead of that plan you can find it's often inspector it and if you think exactly the same way you say I put my job he makes the jobs and it stops when it finds it said William position well I can't exactly follow the same accepted but to apprehend 100 the X In reality all the X and accept the fact that the conduct now is not 2 .period but to dust and if particularly the 0 I find something
With very simple which is a good sign these are "quotation mark but the and so apparently in 1 very compact formula everything is just went deep for amending the agrees co-signers positive identity by their number which is a lot of immunity so I made this number larger stake means that stuck to dust I when I mean the hydrophobic Bob this number this is a negative number admitted by that number which is another meeting I make this number of more negative and so too does is larger so the Vanzant predicts that hydrophobicity it is and hands by often as by far the Felicity is is enhanced by our presence this looks the way that the regiment with what we said .period and actually this is the way the people from the Cal compilation interpreted the results had however intent here but it's not true when you look and discrimination shape it should be a relationship where the slope is all of this sector which by the way something amazing means that this is the parameter which would be extremely difficult to border region that lost was as often as of using sophisticated techniques of imaging and so on and then of the Indian on but here you learn that 2 drops liable to extract quantities to it's really wonderful but it many if you are very optimistic you might say that I can follow is my view that our view from here to here which is striking moment points but not that much not a straight line and when you measure the straight line in the case of this experiment you find free .period something and when you try try to extract of roughness factor on the pictures of the of the of the centers that made you find free .period so if he needs that the people of ventilation should be obeyed but this relationship also predicts things which are not upset In particular the number and told you if signed here becomes Alderman unity it means that you always liquid spreading on the which is a very very important and useful in opposing it here it could be the same if shovel consigned to the role of its sale or . 5 if I have to face who's often as is great it makes 1 .period firemen so it might predict that the side being larger than many teachers pay but this is not the way you see this Red Lion does not cross here July 1 instead there is a chance of a where it somehow saturates and very very slowly it bends the company twitching which is reached on year so it means that it cannot induce comfort waiting by of Michigan and hence hydrophobicity but not to create a new vision of if unification and so it's so it's of course something which is quite important practical but also because it tends legislation shape as is is seems to be obeyed and then beginning but later on the hydrophobic side it seems that it's narrowly now validity to that because of the right to do that to contact the Kennedy very knowledge to tackle knowledge and so you know that I would want jump but it seems that you observed account of discontinuity and we'll come back the data on that so what does it mean what's happening between those red lines which is shared and the blue line which is when you "quotation mark number that we had a few pictures so this was when the pitcher the picture where the liquid follows the accidents of the Soviet in which case I can write what they did here but there is another possibility I said which is the fact that the liquid might choose to invade the cavities of the sun and so the question then becomes why should the Selinda only agreed that do something like that take and I think it's quite so it's it's quite an interesting question so this is a corresponding beaches nobody quit maybe the drop here we to his drop and you know assuming that this sequence has chosen to invade Kennedy and then you say it's here and promises by an amount which is the eggs and the question is is it from and so for that you have to write an energy balance which is the following there is a chance of surpassing energy here which is affiliated with the major John the fact that you create a new social face between sorting and quit OK so have to correspondence of energy which is denies any you suppress your face between 13 and vapor it was dry it's not driving more and you that this is 1 use of the ball you knew that on the surface area which proportional to to the roughness factor because of course it's proportional to the should face but you in vain which is proportionate to our mind or something because you as you know the top of the post the main right here while because the only possibility for having the field which propagates although also on the top of the of the of the of the Monday's is level complete with and of course you can compete with the request would invade it's a question whether we know already what will happen if we do that the will invade everything 1 areas often it's and so here we have to put my a total of men's minus the factions which remains above so when you look at that from the top issue of scene which is policy and use islands which are the right parts and the publisher of dry parts which is given on these very simple designed just tops of the of the design of its support from the before and so this is time DX and again in Sweden cent signature of flying perpendicular picture so if it were a classical if it were like in the arena that's a good feeling National Post media this will be the final lap and so because are his knowledge of immunity and because efforts moribund unity is positive and so we would have that GE negative agreed invading the ghost region In this quantity is negative which means when I go here but "quotation mark is positive and so it means 2 dust more than 92 so this is the usual criterion for we if liquid is sold hide affiliate is a contact is agrees then it should propagated in spot but what is already known in this situation it is a fact that contrasted with the usual Post media when quit his policies this creates new faces between the and
and this is not the case where the weather equipment for this is true when people as junior ministers with his ministers is always the same this was ministers does not enter In the energy balance here you have to create new pieces between liquid and vapor and so if you have assigned press here which makes that this negative please note that yes press again I think because it's too good vapor interface find 1 minus X which is a surface area which is covered by analytical decision it was time EX and so you see that when I use Young's relationship which is there and I express a fragment this season -minus United "quotation mark detail I find that this Friday at 270 negatives the energy lowered when Siddiqui police's is equivalent To go assigned to the non-German something and this something is 1 minus F over all minors and what I like about this expression because that's my definition is number rather than a small are by definition is a member of German unity and so this is a number which is between 0 and 1 and so I can say that the good side of something it's an artificial language which is given by the particle designs of my but nobody should think of indicators and you make it was because the same but higher and higher you do not change anything but you check off and so you say that this unusually effective and so what we find is affected by the quake we go inside the cavity is applied and budget chemical contacting and the 1 given by the president the choice after the quake and the choice of the material which makes a is smaller take the tango with is only a function of the designer prices it's very nice to me that I can decide which chickweed we go inside the Kennedys and which will not again decided by tuning the design or widening adequate but the company between the chemistry and the physics the top in the to think we can see very simple limits here by about shot of vanity rests on it alleging that the peters out so clearly long so it becomes the dimension of the post medium then all because nearly infinite and if our becomes nearly infinite as against Fiji Dessie becomes 90 minutes so it exactly what I said previously the fact that is a classical post media the criterion for Wiki it is just hydrophobicity into contact and there is 1 and ended with entity obligate inside the base of the post if no my opinion is becomes extremely fit the opposite limit so it's nearly flat so it news that the last 1 and then this quantity becomes 1 and so contestants because 0 so here I recovered something which is quite thin due to the fact that required we spread the historian it's a compact and adventures the contact angle has to be smaller than something which is close to 0 so this formula captures and I think between classical despite being and classical wicking saying that includes this very well known which I showed them at the beginning but it creates this intermediate domain where you have is or isn't in so 1st doesn't exist the answer is yes but this is W office only in which is the going to with the post where this Friday and set aside and when you take it up the often drop which is deposited on this you find something like a fried egg you have the yellow the center and other white box here and this tells you much of coexistence between dropped the 1 which is in the state of 1 minute and fear which is propagating inside the prison so the facts but you have a point which is propagating inside the appearance does not mean but you are in the complete with situation he needs not exactly like him I didn't make pitches here you can have the coexistence between these 2 states which is something not so occasion and of
course if you had this coexistence you might be interested in understanding what is a compact rental Trizec cancel this is a kind of exercise that you can do it's quite an easy exercise when you understand clearly what we did here because you get exactly the same kind of argument you can say well later acquitted which is there my dropped he is progressing on both asserting that the queen because the city was a stain of of the kids which was described and so it makes little jumps like this and I can look at the difference of analogy between these 2 situations and when the defense of energy 0 it means that the equilibrium is reached from which we can deduce the contact and made by this drop on on the same degree breasts the faction end of Sunday and of course very logical if we find that this contact and there is not so far from won Of course I was not a off of 1 goes of course this liquid sits on the Senate which means that it should be a very short behind the Phoenix situation but it's never won is a minor something which is strictly positive and this is something that is Of course proportional to the the quantity of something which is still in the hills of the adequate and of course you get understand this formula as a kind of avalanche between what would happen just suddenly quit in which case you would find 1 the equipment said its plan that it is collection which is due to the fact that still of and so would never reach exactly what and so on come back police which is only that's exactly what is this kind to ineligible and each 1 except when the it said 0 and of course 20 died ca 0 if required
spreads and only the fact but to make of half-dozen attend anything it is despite of indeed charade 0 here this is and this is what so I like to finish this is chapter by trying to show you some some of summerhouse new property and what can you do with this behind affiliate so because it's In the case you satisfied his criterion its some the 2 fields and the Getty's which means that at the scale of attend technical if you put such a silly in contact with the back of the grid satisfying this criterion then the liquid was invade source and without interesting questions such as What is the dynamics of Athens but for me the most interesting question is the fact that once knew of the incident Kennedy it is never something which is very special because it's Finland was acquitted if you dates this trip will not move because of the scale all the picture guarantee doesn't matter defense forces are much much larger when you have news of United's gain of US forces dominate politics and the government special something because it's happening having liquid this phenomenon Michael leaves the golf on his blog likes to call it had because it's a it's a it's likely pretty weak but it's hanging in the sense that it is also an interface vapor here and so again think
of using and then we had to show you an example of that so this is a summary of the tub your but you placed in contact with all this sunny days they collided with texture gets into that very small-scale and since the staggering and is fulfilled always chose to invade the Kennedy and so you have this Sunday and finished with grin and now embrace the departed gives on this sunny of solid was equipped with life and then you had drop of can you just like yourself when you do that is a it was sifting the effect which is related to the fact mainly to the fact that the drop of water wood which would have the stock in the classical situation because it's immediately dropped fear being under the queen I am very very easily so who still face can be extremely despicable it's hip it's only situated the sense is that new its ability because it's made of all and so we know but if it is on the grounds that it is the same thing here you suppress the possibility of for your equipment and so it's 1 case where you suppress compact and because you mainly on although is very small in context history that nothing to with usual situation remember I told you at the beginning it's very inadequate to make contact anger he says it's more than a few degrees in this case it was not push it possible to measure quantity because it was too small because it was mainly of adequate and way it's always is trapped in the cavities even if the drop is moving he always remains again at the community for 7 rockets coming you will still have this so this is 1 case where a generator is also need which is the greater the Sofres and as a consequence which is extremely simple another way to see the same thing is to look at the coffee stain effects on this sunny so he should take a drive and you come after I said 1 day this unit the classical got stain effect and in this experiment Dewdrops executive to defend drops of coffee were deposited with the same ones source the size this 1 on 1 part which was without always 1 part with the the audience I didn't get it and because in this case it's completely stability as the coffee in upper weights instead of being built very classically away should somebody this is very unusual for the relies proceeds as a function of time and suddenly pneumonia the pact the populations of particles of cover until you make the stain which has nothing to do homogeneous 1st and the size of course has nothing to do with the size of the classic encompasses so it's another proof that you can generate high instability still faces in this group this in this sites that it said 1 1st example where you see that indeed you can generate the original poverty is using the texture of nests and the city of the final 1 I would like to discuss it is hydrodynamics the fact that you can use of pictures to modify "quotation mark deeply I would say is that the hydrodynamics at interfaces and I would like to take as an example of the very classical question of of individual hydrodynamics which is a blend of offense so you paints ward and you look and the way the paints scenes as a function of time so this article paint does not drive purely quit the Eurofighter and you look at the valuation of the thickness of draft when you lose experiment on effects of you find which is known as the Red row which is 1st the thickness remains constant fall through seconds in case and then in a lot of brought the decrees that immediately following a very nice skating 1 over square of so if you want to us to see where he is come from there is a very nice skating argument about so you have your also it's occurred not only europe the Quinn it's like this the fitness these banks and of course it flows because of that it this is finished this is typical scale the it's in this case 14 I committed called paint it 200 Michael meters so it's very thin films compared to the size of the war and so very naturally you balance to describe the dynamics of this nature balance cottages applying Falls was discussed falls so what we know from Navier-Stokes equation is the fact that viscous forces out that rational velocity the time the viscosity of discussing the easy tops and let ration of the velocity is the unknown velocity at which it .period
divided by the size on which the velocity of areas and the size of thickness because I have no sleep condition here and so close the solid liquid doesn't movement and if you go further and further it moves quicker and quicker and so that the ends of velocity action and so to square because it's an apparition of the universities and this is something that you have to balance with a false billions would you which is the way but you know which is density pension and all this 10 0 what is illegal velocity but the difficulty here is that age is not known because it's a very functional time of course but also an X Tuesday after a while the film has simplified and the way to guess what it is disqualified consist of medicine but there is no characteristics scale on on the verge of X which is the direction of the inner-city so he can be beaten and X all the time and now if you inject 1 very simple relationship in this 1 you find that the thickness of the filets Is the X over raw GT the 100 and if you look and the fitness of your shellfish at even position which is exactly what is that such an experiment you find that indeed it should vary as the inverse of this code of a nice going nowhere you recover in 2 lines this famous you so this is the classical of 1 classical low even in death as short-sighted and the question is how do we modify the slow if you have a solid which is rather more pictures and we are clearly at the height of the case where only quit following this this this this summer and so this is a very recent experiment and a noting that to before the 1st agreement by showed in 2000 and I which is due to be accomplices there and he looked at the dream H on the Sunday which is the collated by they lose all the time when the defendant guides offer such as the senator and he followed the thickness of the Finn but here but be careful about the definition of what I call the thickness of the fish in the thickness of the Finn is the fitness of detection while because at the end of the experiment the numbers the textures of the main finnbay's liquid and so the final fitness is in this definition 0 but don't to actually find thickness is the size of the carrot this would depend of course on the definition of but here I chose as a definition of the as the thickness of the film which is growing because I can says the film which is inside it entertains does not from what is a very interesting of course is the fact that the liquid which is here and it could refuse their and they are interacting the fact that the film is In usually Vermont inside the inside the votes and this remains the inmates when you look at the is that it's completely different to see that the Loeffel aid to the function of time it looks more similar in December to start with regret amended his 2 this flows due to the meeting the strong which is there is not minus 0 . 5 it's minus 1 and this is a very interesting note because it's a low when you have sleep if you have state which means that if the boundary conditions at the frontier between your created and here you know is this because it's served the commission between the liquid and it said in states when he's free to flow distracted but the same liquid you have the possibility of generating slipped and his knowledge of the and the definition of sleep a following 1 when you have a solid and this if you have slipped recently Is is and throwing a love for this season the velocity it means that I just saw the ball and among the various states of velocity and many things especially for you you extrapolate and find 0 0 and you call this length just regrets and is in Norway to quantify the intensity of the sleep when you have the better at that then I sing about visited the Commission In that you can show so it's benefit size of the and it's interesting to potential but in this case each those change this lawful because still willing to Of course still the dividing falls but instead of a square look ancient and so as a fairly quick immediate consequence you see that the fatal place here I find that at age no is Utah X or Ross G. longer too and so this modified I think that I think it is renewable energy
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1st however I was thinking on the I'm sorry about that but they will be slightly shorter in the 2nd Howard promise and of course they would be happy to answer questions now any job you services the Post reported that the In view of the national survey of
the work of the reviews water used to workers that all the operations of the measurement here How is it measured yet so this is our news measurements are made by Dimitri and this is an era of OK and because textures are very the effective effective a clique and measurement by the presence of these pictures and so as you probably know you can
go and to typical skate of the wavelength of light with specific to each of us is widely about living under that they're here because of that we have is warning the the 2 big advantage of accessible thickness here is "quotation mark . 1 I committed to safer to 14 iconic which is the top so here you used the warhead of possibilities of which is nice because you want to better skating lowlands we need all
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