Moth Meets Robotic Flower
How Biomechanics Drives Nature-Inspired Technologies
IAS Senior Visiting Fellow Tom Daniel was the Founding Chair of the Department of Biology and is the Director of the new US Air Force Center of Excellence on Nature-Inspired Flight Technologies and Ideas at the University of Washington.
Prof Tom Daniel, IAS Senior Visiting Fellow, was destined to walk an interdisciplinary path. As refugees from Nazi Germany, his parents had no chance of a proper education before coming to the US. His grandmother, however, was one of the first female physicians in Germany. He spent his childhood in a small American town, burying himself in his grandmother’s books on diverse science subjects.
At a young age, he had already learned to appreciate interdisciplinary sciences and the force of nature, which eventually prompted him to pursue a degree in Life Science, Engineering and Physics. During his PhD degree at Duke University, he met his mentors, Stephen Wainwright and Steven Vogel, who were among the first generation of researchers in comparative biomechanics, a discipline that did not officially exist then.
After visiting their laboratories, Prof Daniel found his life’s calling: “Biomechanics is an impactful science that can give rise to many meaningful applications. The constant technical challenges also mean you get to work with mathematics, cameras and all sorts of interesting tools. And there is pure beauty and elegance in the complex movement of life in nature, which is a joy to behold.”
Indeed, Mother Nature has played a pivotal role in his work. The engineering journey is a series of trials and errors. Evolution is exactly the same. While nature could not build computer-like systems that excel at precise rapid calculations as they are not vital to survival, she has already solved a myriad of problems in the past millions of years.
“Nature is the most experienced and patient engineer ever. If we can derive the principles from her solutions and integrate them into engineering, it can create a huge impact on our lives. Even though we may not be able to reach our goals immediately, we can still make a big difference by moving the field forward,” Prof Daniel noted.
Why Biomechanics Matters
Biomechanics has already given birth to many brilliant technologies, devices and gadgets. Burrs—seeds or dry fruits that grab onto clothes and fur—gave rise to Velcro, the ubiquitous fastener that uses tiny hooks and loops to bind two strips together. The water-repellant paint called Lotusan is modeled on lotus leaves’ microstructure, which interacts with the surface tension of water droplets. Adhesion without glue was conceived by observing the ultra-tiny structures on the feet of geckos.
One of the more famous examples is probably the so-called “cheetah legs”. Cheetahs are known as the fastest animals on land. In the 1990s, biomechanists found an inherent mechanical system in cheetah legs, which deform like a spring when they run. Adopting the principle of muscle elasticity in cheetahs, these hook-shaped prosthetic limbs with a distinct curvature were invented so that amputees could enjoy running like anyone else.
For Prof Daniel, the application of animals’ flight control principles in aerial devices remains his key research area. He believes that flying drones constitute a booming multibillion industry, which has its roots in the unmanned quadcopter for aerial photography, DJI Phantom, developed by an HKUST graduate.
The DJI Phantom, which revolutionized the consumer drone market, was selected as one of the Top 10 Gadgets of 2014 by TIME Magazine.
In one of their studies, his team recorded how moths track flowers when feeding on nectar, using high-speed infrared cameras and 3D-printed robotic flowers with artificial petals and nectaries that can move in various frequencies and directions. The movements of the petals and nectaries stimulate the moths' visual and mechanical sensors respectively. As the petals and nectaries vibrate at different frequencies and in different directions, sensory conflicts ensue, revealing how moths fuse different visual and mechanical sensory information for flight control.
Despite having a brain the size of a sesame seed, moths are capable of tracking complex movements and performing advanced flight functions with the efficiency and accuracy that shame all manmade drones. The research showed that moths’ flower-tracking behavior is multisensory, and surprisingly, mechanical stimuli are the dominant attribute. Even when in sensory conflict, their neural systems do not reweigh the sensory distribution. Also, these creatures can slow their brains to improve their vision under low-light conditions.
“The results shed light on how engineers can design better sensor systems to create flying devices that are more stable and agile, and can adjust to different conditions for medical assistance, disaster relief and even delivery purposes,” Prof Daniel explained.
Using reverse engineering, Prof Daniel and his team built a robotic flower to study moths’ sensory mechanisms during flight.
Beyond Science: Ethics and Collaboration
One of Prof Daniel’s core beliefs is that scientists have a duty to ensure the virtuous cycle of science and nature. Instead of just taking and extracting from nature, we should use our technology and knowledge to better understand and appreciate nature.
He also cautioned researchers about the dark side of science. For instance, flying drones can be used to save lives, but in the wrong hands, they may be deployed to spy and invade privacy. Brain chip implants used to treat Parkinson’s disease can be hacked, and may alter the patient’s sense of identity.
“I believe that faculty, in particular, should instill the kind of mentality in students that they always remember to stop and think about the ethical implications of what they do,” he noted.
Prof Daniel places equal emphasis on the value of collaboration, something he cannot do without in his field. To him, the key to maximizing collaboration is diversity. Teams with members from different disciplines and cultural backgrounds bring a mix of technical skills, scientific outlooks and world views to the table. The more perspectives the team has, the more likely it will be able to solve the problem at hand.
This is particularly important with the convergence of sciences. Life science is becoming more computational and has begun to acquire other domains. Prof Daniel urged his fellow researchers to get out of their comfort zone and embrace interdisciplinary areas, especially biologists who tend to shy away from quantitative science because it is not something they are comfortable doing.
“The best science usually happens accidentally because that spark will be unique. A colleague of mine once chatted with a researcher in information science who was working on approximate computing, and he found a huge parallel between his work on neural systems and the computer that person was building. Such a cross-pollination needs to be encouraged and nurtured,” he said.
As the prior chair of his department, Prof Daniel also attempts to break down the walls between faculty members by asking them to pair up and present each other’s research areas. In this way, they are able to develop a fundamental understanding of each other’s work and explore uncharted research territories together. Meanwhile, he has been visiting HKUST at least once per year to share his research findings at various IAS activities, and engage in cross-regional research collaboration. He has joined forces with Prof I-Ming Hsing of Biomedical Engineering at HKUST on a project that interfaces between engineering and biology. With their expertise in robotics and autonomous systems, the duo is studying an engineered flight system through nature’s inspiration.