Tak-Sing gets inspired and develops new ideas by looking at nature. In 2014, MIT Technology Review named Tak-Sing to their top innovator group under the age of 35. He’s Assistant Professor of Mechanical Engineering at Penn State University where he heads up Wong Laboratory for Nature Inspired Engineering. I love that name. Nature inspired engineering.
His research includes super slippery materials, adhesives and camouflage, all based on what nature has already built.
But what’s interesting is his nature-inspired process and then how he actually develops real solutions.
Here are some other things we talk about:
-How did you get involved with research and using nature as inspiration?
-Can you give an example of research that started with an idea then turned into a research project?
-How do you approach a new project? When something interests you how do you dive in deeper and then set up a research program around that idea?
David Kruse: Hey everyone. Welcome to another episode of Flyover Labs and today we are lucky enough to have Tak-Sing Wong with us. And Tak-Sing researches new technology inspired my nature, and in 2014 our MIT Tech Review named Tak-Sing to their top innovative group under the age of 35. So I’m quite excited to have in with us today. He is the Assistant Professor of Mechanic Engineering at Penn State, where he heads up the Wong laboratory and this is a great name for nature inspired engineering. It sounds like – yeah I love that name, so I – and his research is quite fascinating. People talk more about it, but he has research on Super Slippery Materials and adhesives and camouflage and it all sounds like a Hollywood movie lab. I’m very excited to hear more of what he’s working on and how he gets so curious and what he is excited about. So Tak-Sign, thanks for coming on the show today.
Tak-Sing Wong: Thank you for having me.
David Kruse: So let’s first off and get to know you a little bit better. Can you tell us your background and how you ended up at – eventually at Penn State?
Tak-Sing Wong: Okay, yeah. So I was trained as a Mechanical Engineer and a Materials Science. I did my PhD at UCLA in Chemical Engineering and during that time my main focus was in my goal in actually mechanical systems, software MEM’s, micro manufacturing and Nanotechnology. So that was my background back at PhD and after that I moved to Harvard University to continue my post-op. Over there I studied bio inspired material design where I take ideas from nature, known from their clever strategy and try to translate those concepts into new materials for different engineering applications. So that is where I came from, like mostly mechanical engineering and material science background.
David Kruse: Got you, okay. And where did you grow up?
Tak-Sing Wong: I grew up in Hong Kong. Actually I did my undergraduate over there in the Chinese University of Hong Kong, also in Mechanical Engineering.
David Kruse: Got you, okay, all right. And so what inspired you to come to the United States, just to have the education that you wanted to do what you wanted to do?
Tak-Sing Wong: Right, yeah. So that was a good question. Like when I was a freshman back in college, I was given this opportunity to visit the United States and that program actually brings me to the Biolabs. At that time it belonged to the Lucent Technologies. So Biolabs is really well know where a lot of life scientists will – they will always like originate from Biolabs and I happen to meet some of the scientist over there. So I still remember at that time I was asking them like how can I be one of them in the future. And then like, one of the scientists was telling me that like if you want to work in the Biolabs in the future, the very first thing that you should do is to get a PhD, preferably in the United States if possible. So that was the time when I set my goal to study in the US, yeah.
David Kruse: That’s a great story, and you did it, and now look what you are doing.
Tak-Sing Wong: Yeah, and then I did it. Actually at that time during my college I had a great mentor back in college who – his is name is Professor A. J. Lee. So he offered me a research assistant position at that time and that’s how I stated doing research. And because of those experience that eventually made me to study in the United States.
David Kruse: Interesting, interesting, yeah. And I forget to mention, I mean at the intro that Tak-Sing also has a lot of other awards besides the MIT one that I mentioned and he has been sighted many times in the paper. So he has done pretty well, so I always like to hear how it kind of started and good thing you used that question and…
Tak-Sing Wong: Yeah, yeah, yeah, so yeah it was all stated like when I became a research assistant in professor Lee’s lab at that time, but the reason I was into that line of research was like I still remember when I was a freshmen I attended his lecture. So in his lecture he showed me this one picture where an ant is holding a mechanical gear that is the same size as the ant, it’s like real small. So at that time I was wondering how we can manufacture like mechanical part that small. And then afterwards, after the lecture I came to talk to Professor Lee and he told me this is a whole new area called the Microelectromechanical Systems, where people build like micro device and micromechanical parts that’s very, very small in scale. We are talking about at a length scale that is thinner than a hair diameter, so it’s really small. So I was very intrigued by or excited by the idea of creating devices or structures at that small length scale and that is how I stated doing reached in that area.
David Kruse: Interesting. And what was the first project you worked on in the area?
Tak-Sing Wong: Yeah, the first project I worked on at that time was to move carbon nano tubes to create these thermal sensors, like a temperature sensor. So carbon nano tube itself is of course is made out of carbon and the dimension of the tube is about like, this is like, it’s really, really tiny. You are talking about like a few nanometers. So it’s just to give you an idea, like a hair diameter is around 100 micrometer in width. So like a 100 nanometer is 1000th time smaller than that. So it was like really, really small. We are talking about manipulating a hair of that length scale to a position so that we can create like a temperature sensor. So that was my very first project. And from that project I got to use a lot of like good points. Like for example I get to learn how to use scanning electro microspore, which allows you to look at features that are extremely small, like down to like few micrometer to even down to like 100s of nanometers. And yeah, that was the very first experience I had at that time to the micro and nano scale world and I was like – I was really excited about that during that time.
David Kruse: Interesting. So let’s share a little bit more about your current work and I’m curious how you got involved with more nature inspired research.
Tak-Sing Wong: Right, yeah. So like that, the very first time I started looking into nature was when in was in graduate school at UCLA. So when I was at UCLI as I mentioned, I did like a micro and nano manufacturing. I mixed structures that are on the order of micro meter or nano meters scale. So at that time I was mostly making sensors and actuators for like – like for example, for electronic nodes, that kind of applications. But then like later on I started to look at like other aspects, right. One time I was looking at one of my colleagues in the other lab. They created this super Water Repellent Surfaces and then like I started to ask my colleagues like how did you make it? And then like they showed me some scanning electro microscopic image looking at the surface, of the Liquid Porous Surface. So they are all conscious of this micro and nano scale textures and I was very excited about the idea, because in order to make a Liquid Porous Surface intuitively you want the surface to be very smooth, right. But then they created it as highly rough surfaces and then they can make this surface super repellant, so I was very excited about then. And then like later on they told me about, they are actually are trying to replicate the surface features of a panchkot lotus leaf, because like in nature lotus leaf is found to be super water repellant. If you put a water droplet on the lotus leaf it just rolls around. So that was the very first encounter for me to look at, to know that like – actually nature is a master of nano technology. There is a lot of electro surfaces that utilize nano structures to perform that function. Lotus leaf was one of those examples for water repellency and there’s many other later surfaces that also utilize nano structures to do the same thing. For example Tokay gecko. So you know gecko, they can hear on virtually any surfaces. And if you look at how their feet is constructed, they consist of like – there is micro and nano structures that allows them to adhere on the surfaces through intermolecular forces. So this is another great example of how nature uses nano technology to perform like interesting functions and that is how all this started. Like I was very interested at how natural surfaces utilize nano structures to perform the function. Indeed my PhD thesis at that time was to understand why this lateral surface require textures on the order of nano meter scale to perform the function, specifically water repelling function. So that was my PhD thesis at that time.
David Kruse: Interesting. And so what are some of your current projects that you are most excited about? I know you have a lot.
Tak-Sing Wong: Yeah, yeah, yeah. So one of the most excited projects that I have right now is there is a super slippery surface calls SLIPS. It stands for Slippery Liquid-Infused Porous Surfaces. So this surface was inspired by a type of plant called a Pitcher plant. So probably like you have seen a Pitcher plant before, it looks like a Pitcher. So it is an insect eating plant where like it captures insects for as food. Unlike the Venus Fly Trap that can actually grab insects, Pitcher Plant just stay there. It’s just a static plant that they try to allure the insects to get on to the plant. The way how they can capture the insects is by evolving this super slipper surface at the end of the plant, where insects such as ants, they walk on the surface, and they just get slide off into the plant. So this technology was really like developed when I was doing a post-op at Harvard University at Joanna Aizenberg for that and at that time we were looking into a super slipper and liquid repellent surface that can work in a broad range of environments like high pressure condition, high temperature environments. Because like at that time lotus leaf type of liquid repellent surface has been effectively researched, but it wasn’t able to survive in those environments and that’s why we were looking in a very different type of liquid repellent surface and that’s how this Pitcher Plant inspired material that comes along.
David Kruse: Got you. And so how – when you came across the pitcher plant, can you kind of walk us through how? You see this plant, then what are your next steps? Like how do you analyze the plant? How do you figure out what it’s doing? And then how do you figure out how you can try to recreate it?
Tak-Sing Wong: Right, right, right, right. So like when we began this project, like we actually started off from, not from that above inspired angle, we start from more like a physical perspective. So like let me explain like for the lotus leaf how it works. So like as I mentioned before, lotus leaf it has just a micro nano textures on the surface, right, and the function of these textures is to how to trap a thin layer of air. So when water droplets are hitting on the surface, so it sees just mostly air instead of the textures, it’s kind of like air hocked. So if you happen to play hockey before, when the air is turned on, the object kind of like feels frictionless because it’s sitting on a layer of air. But when you turn off the air and like the object becomes very sticky right. So it’s exactly the same as how the lotus leaf works. The textures help to trap a thin layer of air, so that water just rolls on a layer of air. However, because its rolling on a layer of air it’s not very stable. Typically if you have a high pressure jet of water hitting on a surface or when you are trying to repel at a high temperature, so this air layer can be removed very easily. So that’s why like a lotus leaf type of liquid kind of surface doesn’t survive in those environment, but however the thing about it if you replaced the air with a thin liquid layer. So because liquid in principal is incompatible as compared to air, so it is more stable. You can use it like to repel like a broad range of immiscible liquid and we start from that angle. However when we start a project, we didn’t get the design principal right. So that’s why we start to look into nature to see if there are any relevant or found natural species that use similar mechanism to repel an immiscible object and this is how we come across the Pitcher Plant, because with the Pitcher Plant they also have these micro textures, but this micro textures is helped to trap a thin layer of water such that it can repel ants. Because the way how ants are here on the surface is by this oil layer that is trapped on the feet, so that they can adhere on surface. Because oil and water in human principal and that’s why like a pitcher plant can repel the ends and that’s how we got this idea, how we can trap this liquid layer stably on the surface textures. One thing that we learnt from the pitcher plant idea is how they can devour the surface chemistry so that the liquid layer, the lubricant can stably attach on the rough surfaces or the texture surfaces. So that is like how we learnt the mechanism. And later on we expand this strategy to lubricant that are beyond water. Because pitcher plant uses water as lubricant, but then we start to use like all kinds of lubricant with different surface chemistry, including liquid platform which allows us to repel pretty much anything, including like not only water, but also like blood, oil, ice, bacteria and many more things.
David Kruse: Interesting and so is your technology around the Pitcher Plant, would it be more around, read or manufacturing and discovering the liquid or more of the surface or a combination of the two?
Tak-Sing Wong: It’s a combination of multiple things. First of all we learn about the design principal from the Pitcher Plant, because the slipper surface of the Pitcher Plant consists of the texture surface and lubricating it, so that is the design concept. And then later on we look at how the liquid layer can stably attach on the texture surface without being displaced by the foreign object. So that is the surface chemistry party that we learnt and combining all of this can we create our own slippery surface.
David Kruse: Got you. And what are some potential applications for SLIPS?
Tak-Sing Wong: Right. So SLIPS like is a non-sticking surface. So you can probably think about many applications, things that you don’t want to stick. Examples such as like your cooking time, right, so you don’t want those oil, the grease to stick on our cooking plan, that’s one typical application, but there are many more. For example anti-icing coating. So if you have just a non-sticking coating on your airplane wing, then ice wouldn’t sick on it, or even inside a refrigerator right, like a defroster. So if I didn’t build up on the defroster, then you can save a lot of energy, because we use a lot of electricity trying to warm up the defroster so that they can be used again for defrosting. So that’s one application in the icing and the other application such as Anti-Biofouling coating for medical devices. So bacterial fouling on implants or other medical devices are big problems for the medical industry and so this sticky coating, this anti sticky coating can be put on this medical device so that bacterial biofoul wouldn’t attach on it. Another application is we call this anticoagulanting coating, where blood doesn’t coagulate on the surface. So think about like a blood transfusion or like other blood related or medical devices that if we have just coating, then we don’t need to put an anticoagulant onto the blood so that like it won’t be clotting the device, so that’s more bio-medical. Other application such as anti-fouling coating on ships; you know like when a sea creation such as a barnacle attaching on the ship will – it creates a lot of drag, which means that you need more energy to propel the ship across the ocean. So that’s a big problem. So anti-fouling coating is one of them. And also like anti-graffiti coating. So we can put it on road signs and also on public infrastructures so that people wouldn’t be able to put graffiti’s on those things. And there are many other more applications that where non- sticky coatings are highly desirable and some people put it inside like bottles. Like for example, you can clear out the food content or ketchup much easier right, so there are some other demonstration people who showed that. One big application that right now our lab is really interested is to put it on sticky waterless toilet. One of the key reason why we need that much water to flush our toilet is because our human waste are sticky, I mean everyone knows. So what if we have this super non-sticky coating that things doesn’t stick on it. We can potentially save a lot of water. We are talking about like many, many gallons of water and so this is something that like we are actively looking to do that, among many other big impact applications.
David Kruse: Wow! Yeah, I can imagine there’s just many, many applications. And so what I’m curious is about is for each of these applications whether it’s on a ship or the toilet urinal, do you have to engineer specifically for that material since you are kind of looking at the liquid plus the surface.
Tak-Sing Wong: Yeah, that’s a great question yeah. So SLIPS is just as a concept, it’s just a lubricator surface right. So depending on a specific application, we need to specifically tailor or engineer the composition, both the lubricant and also the surface chemistry, as well as the surface textures. And so yeah, so each application requires specifically, clearly the composition of the SLIPS coating.
David Kruse: And is it possible or maybe its gets too technical, but expand on how do you look at the surface of the ship versus a toilet and how would you alter the liquid in order to properly adhere. Yeah, what are you looking at, and what’s going through your mind when you got to deal with that?
Tak-Sing Wong: Right, right. So the very first thing that comes to mind is what kind of material that is going to be repelled, because like having that knowledge then we know what kind of lubricant we should use, because for the concept of SLIPS we need to find a lubricant that is immiscible to whatever you want to repel. So the things cannot be mixed. Like for example you just want to repel water, then you can find a lubricant that doesn’t mix with water. But if you want to repel both water and oil, then you need to find a lubricant that is immiscible to both liquids, right. So that’s the very first thing to come in mind. And once we know which kind of lubricant that we are going to use, then we need to tailor the surface chemistry of the surface such that the lubricant can ahead on to the underlying solid and that’s the second thing. The third thing is the solid itself. In a lot of applications this solid is fixed. For example for a toilet, most of them are made of ceramic or like or some of them are made up of metals. So then like that solid material is fixed, so we don’t have that much freedom on that. So we pretty much work around that materials and then figure out a surface chemistry, because we know what kind of lubricant we need to use. Then we just work around with all this design criteria that we make the surface depending on specific applications.
David Kruse: And how do you figure out what, you know what type of liquid to use. I know you said if you want to repel water and oil, well you obviously can’t use oil because, and so is this just a body of materials out there that you and all the researchers know about. Are you like looking through kind of more novel materials?
Tak-Sing Wong: Right, yeah, so I think for the lubricant part like there are many off the shelf lubricants that just has been developed by a lot of like chemists or chemical engineers over the years. Some of the lubricant is highly water immiscible and some of them are both oil immiscible and water immiscible. Just to give you an idea there, for example one of the lubricant that we use is called proformative oil. So the surface chemistry is very similar to Teflon, so it’s kind of like liquid Teflon. So that particular lubricant is both immiscible oil and also water. So that is just one of the lubricants that we have been using for many different application. On top of that if your application requirement only requires to repel water for example, then you can use just oil for example, like plant oil. Because plant oil and water, they are not immiscible, so you can use those lubricants for that type of application. So that broad range of lubricant that you can get off the shelf and they have, they come with a specific property and immiscibility was definitely great, it’s just that you will find the right one.
David Kruse: Got you, okay. And what stage of the development is SLIPS in right now?
Tak-Sing Wong: So, for the SLIPS – so SLIPS the very publication it came out in 2011. So it’s been about five years now and so of course from the academic side there are great developments over the last five years. If you go to search in the literature, like Google’s column, you probably would see our very first, first publications is site for more than like 600, close to 700 times and so there is a lot of interest in that area. For the commercial aspect, that like my mentor, Johanna Isenberg at Harvard University, she and also one of my previous colleague Phil Kim, so they stated a company called SLIPS Technologies and now it’s based in Boston. So that company right now is focusing on commercialized SLIPS coating for industrial applications and that company started about for two years by now and I think they have been doing really, really well.
David Kruse: Interesting. Well they needed to start in Boston, that’s interesting.
Tak-Sing Wong: Yeah.
David Kruse: I’ll have to check that out. Yeah, I mean there is – if you can figure out, man there is so many applications, it’s very interesting.
Tak-Sing Wong: Yeah, there are many applications of that, yeah definitely.
David Kruse: And so I’m curious, maybe do you have another project that you could share that you are working on that you are excited about.
Tak-Sing Wong: Yeah, definitely. So like one of the interesting research direction that we are pursuing is what I call the cross species materials. So if you look at of field of Bio Pneumatic or Bio Inspired engineering, a lot of time people just look at one specific species, for example the lotus leaf and then they just replicate that specific species property, for example like a liquid tolerance right, just one species and then one property. People – but there are lot of possibilities here, because we can actually take the property of the lotus leaf, we pick the property of the butterfly wind, we pick the property of the Tokay gecko and combined all of them together into one material, so that this material will have multi function properties right. So this is kind of like crossing different species and combine them into one material. So this is like one active research direction that we have been looking at. So far we have developed a field of cross species materials. So one of them is we try to incorporate the property of the lotus leaf, the property of the pitcher plant, the property of the rice leaf, combine them together to create what we call directional slippery rough surface. So this material allows us to very efficiently remove water from steam or water vapor. So we can think about like applications such as a power plant or a dissertation plant where we have to constantly convert water steam into water droplet, so that we can remove the heat away from heat exchanger or we need to convert the steam into water, so that we can collect the finalized water for like collection, for example. Also another application is fog harvesting. So fog harvesting, the principal is you try to collect water from air. So like you know like in air we have a lot of water vapors in very tiny water droplet forms. But collecting them is not easy. So like using the slippery rough surfaces we can collect them from air very efficiently. So it potentially can be used in remote area where it is too expensive to build us a water dissertation plant, just by having the surface sitting there that we can start collecting water. So these are some just application examples where we can use the idea from different biological species combining into one material for like a multi functional engineering purposes.
David Kruse: And how do you decide what parts of those different plants, the rice leaf and the pitcher plant and the lotus leaf, how do you decide what to take from each one of those?
Tak-Sing Wong: Right, right, yeah that’s a great question. I think that involves a lot of creativity there. Because you can think of so many different natural species out there right and combining them, some of their functions are compatible, some of them are not. So let’s take the fog harvesting example as an application example. So for fog harvesting we want a surface, first of all we need it to be a high surface area so that it can collect a lot of water vapor per unit time and for that we want a surface to have to be rough or to have surface texture and that is something that we can take idea from the lotus leaf, because lotus leaf it consists of micro nano structures and it has a very high surface area. So that is one feature we can take from the lotus leaf. The second part that is important is once we collect the water on to the surface we need to remove them as fast as possible and on that we need a surface to be really slippery. So with that idea, we can take the idea from the pitcher plant, because pitcher plant as well as the lotus surface is very slippery. So we can combine a high surface area of the lotus with the lubricant surface of the pitcher plant and now we have two components there. And the final component is the rice leaf. So rice leaf on the surface it has directional micro groves which allows the liquid to be transported in one direction, and by combining this function into the high surface area and also the slippery component, then we can create a surface that first of all can collect water very efficiently because it has a high surface area. Second of all it’s so slippery so the liquid can be removed very fast and it’s directional, which insures that we can collect water in one specific location. So by combining these three functions which is inspired by these three different natural surfaces, we create a surface that allows us to collect water from air very efficiently. So that’s kind of the rational, the design idea of how we can get an idea from different plant species.
David Kruse: And what was it called, the water from air, the harvester, what was the…?
Tak-Sing Wong: We call that a slippery rough surface.
David Kruse: Okay, was there a harvesting in the name at all?
Tak-Sing Wong: Fog harvesting.
David Kruse: Fog harvesting.
Tak-Sing Wong: F-O-G harvesting.
David Kruse: Oh! Fog Harvesting, cool. All right, got you. That’s a good name. I like it. And how much surface area do you need or what have you done in your research, like how much water can you capture? I know it’s probably early stages, but just curious?
Tak-Sing Wong: Okay, so it’s all by comparison right. So like compared to typical smooth hydrophobic or we call it super hydrophobic surface. So the slippery rough surface can capture at least three to five, like three to five times more water than just this regular hydrophobic surfaces.
David Kruse: Interesting. Wow!
Tak-Sing Wong: And of course like we haven’t – we are still optimizing the surfaces and we expect that that can even capture more water in the future.
David Kruse: And with that project, do you start with the kind of application in mind or do you say, hey, we could probably pull these unique features from these different nature inspired material, you now the plants and leaves. So do you start with like kind of the problem you’re trying to figure out or do you figure out the problem after you have some unique technology that you pull together from multiple sources.
Tak-Sing Wong: Right, it actually goes both ways. Like the way we how we come up with projects or ideas in my lab, one way is we start with our big problem. For example water is a big problem, right, how we can get clean water. So then like starting with a big problem, then we start to look into nature. How insects or plants or animals solve this problem. Then we take ideas from their strategy to see whether we can translate that into big ideas or material so that we can use it, so that’s one approach. The second approach is we look at some lateral species to see if they have some really clever or cool strategies that we can learn, and then like we development fracturing technologies to build us structures or materials and then we look for engineering problems where we can apply these materials to. So it really is like a two way. Like one way is starting from the problems, we look for natures solution and the second is we look for some cool things in nature and then we look for problems how this cool strategy and materials can be used to solve some important problems.
David Kruse: Interesting. And what do you want to have your technology become like. All right, you mentioned that one, the SLIPS technology is that they started a company with it. Are you looking forward to work with companies or are you interested in just getting on to the research community or all of the above or kind of what are your goals with it?
Tak-Sing Wong: Yeah, like academically like of course we want to develop some new technology or now for a research area that we are certainly excited about so that they can start to follow and study further. But on the other than we just, we don’t just limit it on laboratory experiment. We really want to develop some technology that eventually everyone can be benefit from, like everyone can use it. So one of the long term goals that I have, like for example like if there is some technology that we can license to a company that would be great. And also like if the timing is right, then we probably will also start our own company to commercialize this technology, so that like everyone can use them eventually.
David Kruse: Got you, that makes sense, okay. And we are getting near the end of the podcast unfortunately, but do you – is there any other technology you want to mention?
Tak-Sing Wong: Right, yeah, so I think that’s pretty much the technologies that right now we are researching in the lab. The key is really like learning some highly engineered surfaces from nature and how we can use them for some very important applications. Non-sticky coating is a big research area in our group, because there is just so many things that you can do with it, there is so many applications and we are very excited about the potential of them.
David Kruse: Yeah, I mean if the most hospital services and medical devices are coated, I mean that would just save so many lives.
Tak-Sing Wong: That’s right, that’s right, that’s right.
David Kruse: It’s a major, major issue. I mean there is also – I actually had a fun question around that. Have you thought about testing it out on a water slide? Do you think it will improve the speed?
Tak-Sing Wong: Yeah, like those are like some possible applicants, like indeed before like some company group contacted us to see if we can put like SLIPS or slippery coating on to some of this application to improve the speed and things like that, yeah, those are defiantly some of the really cool applicators.
David Kruse: Yeah, they are awesome. We are in Wisconsin, so we are the home of the water part, especially the indoor water parks, so…
Tak-Sing Wong: Here we go.
David Kruse: That’s kind of more of a fun – that’s a little different than saving lives at a hospital, but they both have their value I guess in a different way.
Tak-Sing Wong: That’s right, that’s right, yeah.
David Kruse: Well yeah, unfortunately I think that just about does it. But I have many more questions, but we should probably stop now and I really appreciate you telling us, I mean telling us about what you are working on, but also just kind of how you think about stuff and how you come up with new ideas and how you put them together, that is quite interesting, so we definitely appreciate your time.
Tak-Sing Wong: Yeah, thank you. Thank you for having me again.
David Kruse: Yes, and thanks everyone for listening to another episode of Flyover Labs. Hope you enjoyed it as much as I did and we’ll see you next time. Thanks Tak-Sing and thanks everyone.
Tak-Sing Wong: Thank you.
David Kruse: Bye.