Wednesday, July 14, 2021

Secret Science Club Zoom Lecture Recap: Walk, Don't Run

Tonight, my great and good friends of the Secret Science Club presented a Zoom lecture featuring Dr David Hu, engineer and animal locomotion researcher. Dr Hu is a professor of mechanical engineering and biology and an adjunct professor of physics at Georgia Tech, and his latest book is How to Walk on Water and Climb up Walls: Animal Movement and the Robots of the Future. Dr Hu had a brush with the political world when Senator Jeff Flake called some of his research wasteful. I like him already, and the lecture is just starting. 

Dr Hu began his lecture with the heights of his career- the two times when he won the Ignobel Prize for studying how animals pee, and another one for studying the cubic feces of wombats. He recounted a 5/25/2016 Fox and Friends story about his 'wasteful' studies and his call-out by Jeff Flake, who accused him of being responsible for 15% of the nation's most wasteful studies (his study about how many times a dog needs to shake to get rid of moisture actually has a bearing on applying medication to the scalp). 

Dr Hu then joked about how he was admitted to MIT by mistake, then began the lecture with a video of water striders, which use hairs on their legs to repel water in order to walk on the surface. Dr Hu noted the beauty of fluid mechanics, showing a picture of a water strider walking on dyed water, and kicking up vortices. Wataer striders use their legs as oars which sweep across the miniscus of water.

Dr Hu then displayed a video of a basilisk lizard running across a body of water- its legs form an air cavity that it slaps against. 


If a human wants to run on water like a basilisk, it would need trashcan lid sized feet and legs fifteen times as strong. To emulate a water strider, the feet would have to have a 10 kilometer perimeter. 

Dr Hu noted that water strider emulating robots could search for oil slicks on the water. 

Dr Hu decided to study cats because they are 'champion animals'. Besides being champion sleepers, cats are super clean. Their tongues are covered with spikes (feliform papillae), which are used for grooming. Each papilla has a concavity which uses capillary action to fill itself with saliva, a natural detergent. The concavity in the papilla matches the hair. Cats use about three teaspoons of saliva each day for grooming, and use saliva to keep cool, in lieu of sweat. Dr Hu patented a cat tongue inspired hairbrush. He joked about cats' ability to form hairballs to deposit wherever they wish. 

Dr Hu then went on to discuss dogs- nobody had studied the drying shake of a dog, whcih starts at the head and travels back. Shedding water is a matter of life or death- a forty pound Labrador would retain about a pound of water after a dip. Fur evolved to keep animals warm and dry, so they need to be able to dry off. Mice, as well as dogs, shake. A rat closes its eyes before shaking because it produces about 20G with the shake. Why can't humans shake dry? Dogs have an adaptation, they have loose skin which can move under the centripetal forces produced with shaking. 

Having shown us enough cute mammals, Dr Hu focused on fire ants- ants are discete, but flow and coalesce like liquids. Not too far from the Georgia Tech campus, fire ants can be collected. In the lab, they put ants in buckets of water to demonstrate rafting behavior. The ants adhere to each other and form a water repellent mass with air pockets. 


The ants with coalesce to form a solid monolayer when there are many ants. and their structure is elastic. They link and delink to react to the environmental conditions. These models can be the basis of swarm robotz which could, for instance, build bridges. 

Dr Hu then shifted to a scatalogical vein. While he was changing his children's diapers, he decided to measure how long it taakes animals to urinate. Small animals don't have the mass to produce enough pressure to form a stream, and form droplets. Baby rats need their mothers to lick their urine from their urethra. He then showed a remarkable video of an elephant urinating and defecating simultaneously. An elephant has a bladder which can hold up to twenty gallons of urine, but most animals take an average of about twenty-one seconds to empty a bladder. Torricelli's Law relates the speed of fluid flowing from an orifice to height of the fluid column above it. The study of the duration of urination is important because it can be used to calibrate artificial collegen urethrae for medical patients. 

The lecture ended with cuboidal scat, which necessitated a trip to Australia, where he collaborated with wombat expert Dr Scott Carver. Because wombats are burrowers, their pouches face towards the back, so the joeys get pooped on. Wombats defecate in latrines, usually raised areas. Why does the bare-nosed wombat produce cubic poop? They probably use their poop as area markers to delinate their home ranges, building 'cairns' of poop. Wombats do noHy ahowed a CT scan of a wombat poophole. He showed a slide of a roadkilled womba, noting the ten meter long large intestine, sliced open to show how a fecal slurry has moisture removed until a dry fecal cube is formed. He compared the shaping of wombat poop to the fomation of the Giant's Causeway as rock cooled. Wombat intestines have stiff sections (four to one in proportion to soft sections) which contract quickly, forming the corners of a fecal poop cube. 

The lecture was followed with a Q&A session. Regarding funding, Dr Hu opined that he thinks biology is in trouble, with the ongoing extinction event and increased interest in human diseases. There are more tigers in captivity than in the wild, elephants may go extinct in our lifetime... he have a lot to learn, but little time. Regarding his kerfuffle with Flake, he urged scientists to fight back. He responded in Scientific American and Flake caved, asking Dr Hu to find the real wasteful spending. Dr Hu declined the offer. The funding for attacks on science continues, though. Why don't cats get sick more often when they swallow dirt? Dr Hu noted that the alimentary canal is one tube from mouth to anus. Stuff such as ticks gets digested, they clean their butts with their tongues, and are okay... if people did that, they'd probably get sick. Asked about robots based on biomimicry, Dr Hu noted that animals are the only models to base water walking or rubble crawling robots.  Dr Hu has upcoming research regarding earwax, which probably has insect-thwarting properties. 

Dr Hu delivered an informative, funny lecture, with a bit of political snark and a heaping dose of advocacy.  He's a very engaging speaker.  Kudos to him, and to Margaret and Dorian.   For a taste of the Secret Science Club experience, here's a video by the Good Doctor: 

Pour yourself a nice beverage and soak in that SCIENCE!!!


bowtiejack said...

Very nice. Thanks.

emjayay said...

I think it was Sarah Palin who made a big deal about some federally funded fruit fly research. Fruit flies are used for research because they are easy to raise and have very short generations. Basis science research is usually about stuff that seems trivial but can be important bits of information leading to increased knowledge and understanding and sometimes eventually major breakthroughs. Also Palin was a simple minded charlatan demagogue who was a step in paving the way to our former stupid con man president.

Richard said...

Hello emjayay. I remember those comments. I think it was a Republican talking point at the time. It probably was Sarah Palin who delivered the message. That's when i realized i will never be young anymore. It was a wake up.