David Hu: Studying the Biomechanics of Animal Locomotion

David Hu ’97 is an Associate Professor of Mechanical Engineering and Biology at Georgia Tech. Dr. Hu has applied his expertise in the mechanics of interfaces between fluids such as air and water to the biomechanics of animal locomotion, publishing papers ranging from why frog tongues are so sticky to how fire ants form waterproof rafts. His work has been published in high impact journals including Nature (2003, 2005) and PNAS (2009, 2011, 2012, 2014) (all publications available in pdf at http://www.hu.gatech.edu/publications), and featured on Good Morning America, NPR, the New York Times (2013, 2017), National Geographic Magazine and USA Today. Dr. Hu has been recognized with the prestigious NSF CAREER award, Lockheed Inspirational Young Faculty award, and the lighthearted but coveted Ig Nobel prize. Below, he chats with Xinyi Zhou ’10 about his experiences in the Magnet, how he became a professor, and his research today.

Dr. David Hu, Georgia Tech (photo by Candler Hobbs)
Tell us a little about your Magnet experience -- what classes and clubs do you remember? What teachers were memorable? 

I remember I was in Ms. Sandoval’s class in Chemistry. I got a borderline grade on a final exam and she convinced me to join the cross-country team. Ever since then I've been running every day. The cross-country team was really, really good for me. It was a team of other nerds. I guess everyone in the Blair magnet is nerdy but cross-country was especially so. It's really challenging and uplifting to go running. She basically taught me a lifelong skill.

With Ms. George, she's probably retired, we used to go on this trip to Wallops Island. You go crawling around on your stomach in the mud, like a turtle.

Yeah, I went to Wallops! We did that.

That's great, they keep it alive! I grew up in the suburbs so that was my first experience of the real outdoors. I don't have any degrees in biology but I'm a professor of biology, and I think part of appreciating nature started with taking her Marine Biology class.

Another thing is the research projects in [junior] year. The teamwork was painful but useful to go through. I also started to realize there are some really smart people in Blair. 

The big thing about Blair was that I did the SRP (Senior Research Project), which got me into MIT. If I didn't do this research project that was supported by Blair -- I worked at NRL (Naval Research Laboratories) -- if I didn't do this project I don't think people would have recognized that I have any scientific talent . . . I was a Westinghouse semifinalist -- that was a really big deal for me; that was the first time I was nationally recognized.

How did you decide to major in mechanical engineering in college?

I think I've always been someone who likes hands-on things. I'm not convinced about things unless I see them with my own eyes. When I was at MIT, I took a physics class on mechanics and I really liked it. You could really predict things with a few simple equations. You could understand where to put the doorstopper or how do you design bookshelves so that they don't break when you put books on them. So I decided to pursue that part of physics. And I sort of did a double major in applied math, since you could do a minor in with your MechE degree and that was really influential.

So you then did a PhD in mathematics?

It was in fluid mechanics in the math department. MIT's math department is one of the four math departments in the US that have a lab. It might be more now, but they actually do experiments and do calculations to see how they get those results. I liked the natural world and I wanted to figure out tools to study and understand it. I met this professor named L. Mahadevan, he's at Harvard now, but he was in the MechE department, and the nice thing about MIT is every undergrad has to have an advisor. He's the first professor I met that seemed to do research about everyday life. He wrote papers on like, what's the best way to cut a turkey, how do knives work -- is it better to make them serrated or is it better to make it straight. He wrote papers on Venus flytraps and why flowers bloom and what the shapes of leaves are. As soon as I saw that, I knew that was what I wanted to end up doing in my career.

How does someone succeed in academia today, especially when you want to do something that seems less practical? How did you become a professor?


I think the thing that actually saved me is that we do calculations. We discover new kinds of physical principles and I can support it with math. That's the only thing that allows me to be silly and still be taken seriously sometimes. Because the math makes it so that the things we discover are permanent and real, they're always there.

Working on weird things, I don't think it's for everybody, but it's definitely for me. It gets you attention, and it can be good and bad. A lot of the grants I got were because program officers saw my stuff in the New York Times or the Washington Post or USA Today. People saw this and thought, this could lead to something that David didn't even think about yet. Attention is a double-edged sword; I was publicly criticized by a senator on Fox & Friends last year. It was very stressful. It's kind of unintentionally made me this spokesperson for weird science. All science should be done, but especially the weird science.

You had asked me how I got this job. The nice thing about studying animals these days is that there are a lot of applications in science and engineering. And this is not something I knew in college on in high school, or even in grad school; it's really something I noticed writing grants and making my name as a permanent faculty member. A lot of things that people are trying to do, are things that are done in nature, but almost impossible to make with robots and human made devices. We can make a lot of progress by understanding how things work. It's not a big field but it's big enough to have a lot of people working on it. It's enough to have a pretty good career. When I did the faculty job search I didn't have trouble finding a job. A lot of times people will take something they don't know they're looking for. I don't think anyone at Georgia Tech was saying, we're looking at someone who puts ants on water and puts snakes in socks. I was able to convince them that this is an interesting field and they'll be able to attract mechanical engineers. Georgia Tech made a bet on it and I think they bet pretty well.

I think the number one concern of graduate students is that their advisor seems really stressed and the prospects for a job seem really slim. I've seen this all around me, but if you are really original, and fearless, sometimes there's this saint that protects you. It's like when you're playing Hearts and you're shooting the moon. It helps you stand out from the crowd and that's half the game.

How would you describe your underlying approach to research?

I've been a professional scientist for about ten years, if you count the PhD it's almost 15 years now, of making money off coming up with ideas that people didn't think of, and trying to figure out if those ideas are true and telling it to the whole world. I think that's what my job is. I don't think a lot of scientists think of the last part as part of their job. But it's part of the job I've really practiced and really liked. My approach to research is one part, I try to be as original as possible. I try to figure out what is the one thing in this field that would be really surprising and bring a lot of new understanding. Two, I try to tell it to as many people as possible and tell the story of this research in a way that is almost like a fiction book. Nature's so bizarre. We use a lot of photography in my lab. I hired the whole Georgia Tech yearbook team to join my lab and we took a lot of science photos. Photos of mosquitoes getting hit by raindrops (that one actually got into National Geographic), photos of elephants urinating, and these things, people have never seen that. But when you look at it through the lens of photography it's really beautiful. I think that's part of my secret -- I look at where photos are really important and useful.

Looking at your papers, it seems like you use a lot of different techniques -- how do you make progress in research when you need a lot of diverse expertise?

I'm driven by questions, so once we have the question right, and we have the right animal, then we figure out what tools solve the problem. That's where the students come in. One thing I've realized about science is you get out of touch [of bench work] really quickly. The only way I can get results is because the students bring skills to the table I don't have, that didn't even exist before. There are a few students who are makers and 3D print things.

Studying biology, there are no rules. It's like the wild wild west, you really have to figure out what's going to do the job and you often have to figure out new tools for every animal. I meet the student and see what skills they have and what projects could fit. I don't really have the tools anymore; I just have a really good eye for projects. We do what's called table top science -- we're usually measuring things or trying to visualize things. So I try not to get too too high tech. I've published a lot of papers just by describing what happens, and trying to understand why that happens. That's where the math comes in.

Going back to science outreach, what do you think are the current challenges in explaining the value of science to the public? How do we reach people who don't read National Geographic and might not read newspapers like the New York Times either?

Dr. Hu accepts the Ig Nobel Prize
I agree with you -- the New York Times and National Geographic are basically to an audience that already believes that science is discovering truth and science is important and nature is beautiful and should be conserved. So when we publish, I try to tell our news people to get this stuff into other [news outlets], such as USA Today. When we measured the length of eyelashes, we got into beauty blogs. I think my response to the senator was also read because I wrote a response in Scientific American so there's a chance that science skeptics actually read it. I've tried to self-invite to the Republican National Convention but I haven't been invited yet. I think it's a big challenge but the more we put our stuff out there, the more we use photographs and video, the more chances that someone on the other side is going to see it. Because photographs aren't really pro-science or anti-science, they're just documenting the way things are. The more anti-science people see these beautiful things, they might actually see the other point of view.

I teach a class at Georgia Tech about science communication. We get together every two weeks and we talk about photography, storytelling, website making -- how to prepare for when your research is picked up by the news. We make this press kit for journalists, so they have all the interesting tidbits and any pictures that can help get it disseminated. There's a lot of pushback among academics. There's a lot of people that don't see the importance of talking to journalists, many professors disdain it, and you can be a grad student for five years and never learn how to talk to journalists, and I think it's really bad for the field.

Math is very difficult to talk to general audiences. Even though a lot of people look at my papers and see the math, they think I'm a mathematician, I talk about the story that the math tells. My pee pee paper (pdf) came from changing diapers, my eyelash paper (pdf) from my daughter being born and she had long eyelashes. And I also do it because I like to look back and think of my family and where I was in life at the time.

It seems like you get your ideas from everyday life.

Yeah. That's the great thing about biology, the vestiges of evolution are all around us. In one lifetime I won't be able to understand all the things but if I can kind of understand a few interesting tidbits that might have some engineering applications, I'll be pretty happy.

Is there any research you want to talk about right now?


There’s this article that's going to come out tomorrow in Bioinspiration and Biomimetics on why bees are so hairy. We find that they're hairy because they act like a carpet when the bees capture pollen -- they capture 30% of their weight in pollen every day! The pollen gets embedded on the tips of their hairs and that allows for easy grooming. They groom using their arms -- imagine their arms are covered in little Christmas trees, and the hairs on their arms are really tightly spaced so they can use them as tweezers to pick out pollen. They can remove over 15,000 particles in three minutes, they’re really fast. It's the first time anyone's tried to get quantitative, tried to count and figure out why bees are so good [at pollen capture and removal].