Brown researchers build robotic bat wing

The strong, flapping flight of bats offers great possibilities for the design of small aircraft, among other applications. By building a robotic bat wing, Brown researchers have uncovered flight secrets of real bats: the function of ligaments, the elasticity of skin, the structural support of musculature, skeletal flexibility, upstroke, downstroke.

PROVIDENCE, R.I. [Brown University] — Researchers at Brown University have developed a robotic bat wing that is providing valuable new information about dynamics of flapping flight in real bats.

The robot, which mimics the wing shape and motion of the lesser dog-faced fruit bat, is designed to flap while attached to a force transducer in a wind tunnel. As the lifelike wing flaps, the force transducer records the aerodynamic forces generated by the moving wing. By measuring the power output of the three servo motors that control the robot’s seven movable joints, researchers can evaluate the energy required to execute wing movements.

Wing of bat in life and lab
A robotic bat wing lets researchers measure forces, joint
movements, and flight parameters - and learn more about
how the real thing operates in nature.
Credit: Breuer and Swartz Labs/Brown University

Testing showed the robot can match the basic flight parameters of bats, producing enough thrust to overcome drag and enough lift to carry the weight of the model species.

A paper describing the robot and presenting results from preliminary experiments is published in the journal Bioinspiration and Biomimetics. The work was done in labs of Brown professors Kenneth Breuer and Sharon Swartz, who are the senior authors on the paper. Breuer, an engineer, and Swartz, a biologist, have studied bat flight and anatomy for years.

The faux flapper generates data that could never be collected directly from live animals, said Joseph Bahlman, a graduate student at Brown who led the project. Bats can’t fly when connected to instruments that record aerodynamic forces directly, so that isn’t an option — and bats don’t take requests.


Brown U. researchers build a "robatic" bat wing from Brown University on Vimeo.

“We can’t ask a bat to flap at a frequency of eight hertz then raise it to nine hertz so we can see what difference that makes,” Bahlman said. “They don’t really cooperate that way.”

But the model does exactly what the researchers want it to do. They can control each of its movement capabilities — kinematic parameters — individually. That way they can adjust one parameter while keeping the rest constant to isolate the effects.

“We can answer questions like, ‘Does increasing wing beat frequency improve lift and what’s the energetic cost of doing that?’” Bahlman said. “We can directly measure the relationship between these kinematic parameters, aerodynamic forces, and energetics.”

Detailed experimental results from the robot will be described in future research papers, but this first paper includes some preliminary results from a few case studies.

One experiment looked at the aerodynamic effects of wing folding. Bats and some birds fold their wings back during the upstroke. Previous research from Brown had found that folding helped the bats save energy, but how folding affected aerodynamic forces wasn’t clear. Testing with the robot wing shows that folding is all about lift.

Studying an animal with unique abilities
Over the years, Kenneth Breuer, an engineer, and
Sharon Swartz, a biologist, have developed a large
archive of bat data, from wind tunnels to field
studies and slow-motion video.

In a flapping animal, positive lift is generated by the downstroke, but some of that lift is undone by the subsequent upstroke, which generates negative lift. By running trials with and without wing folding, the robot showed that folding the wing on the upstroke dramatically decreases that negative lift, increasing net lift by 50 percent.

Data like that will not only give new insights into the mechanics of bat flight, it could aid the design of small flapping aircraft. The research was funded by the U.S. Air Force Office of Scientific Research and the National Science Foundation..

Inspired by the real thing

Bat wings are complex things. They span most of the length of a bat’s body, from shoulder to foot. They are supported and moved by two arm bones and five finger-like digits. Over those bones is a super-elastic skin that can stretch up to 400 percent without tearing. The eight-inch robot mimics that anatomy with plastic bones carefully fabricated on a 3-D printer to match proportions of a real bat. The skin is made of a silicone elastomer. The joints are actuated by servo motors that pull on tendon-like cables, which in turn pull on the joints.

The robot doesn’t quite match the complexity of a real bat’s wing, which has 25 joints and 34 degrees of freedom. An exact simulation isn’t feasible given today’s technology and wouldn’t be desirable anyway, Bahlman said. Part of why the model is useful is that it distills bat flapping down to five fundamental parameters: flapping frequency, flapping amplitude, the angle of the flap relative to the ground, the amount of time used for the downstroke, and the extent to which the wings can fold back.

Experimental data aside, Bahlman said there were many lessons learned just in building the robot and getting it to work properly. “We learned a lot about how bats work from trying to duplicate them and having things go wrong,” he said.

During testing, for example, the tongue and groove joint used for the robot’s elbow broke repeatedly. The forces on the wing would spread open the groove, and eventually break it open. Bahlman eventually wrapped steel cable around the joint to keep it intact, similar to the way ligaments hold joints together in real animals.

The fact that the elbow was a characteristic weak point in the robot might help to explain the musculature of elbows in real bats. Bats have a large set of muscles at the elbow that are not positioned to flex the joint. In humans, these muscles are used in the motion that helps us turn our palms up or down. Bats can’t make that motion, however, so the fact that these muscles are so large was something of a mystery. Bahlman’s experience with the robot suggests these muscles may be adapted to resist bending in a direction that would break the joint open.

The wing membrane provided more lessons. It often tore at the leading edge, prompting Bahlman to reinforce that spot with elastic threads. The fix ended up looking a lot like the tendon and muscle that reinforce leading edges in bats, underscoring how important those structures are.

Now that the model is operational, Bahlman has lots of plans for it.

“The next step is to start playing with the materials,” he said. “We’d like to try different wing materials, different amounts of flexibility on the bones, looking to see if there are beneficial tradeoffs in these material properties.”

- by Kevin Stacey

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Brown Engineering Alumni H. David Hibbitt Ph.D. ’72 and Enrique Lavernia ’82 Elected to the National Academy of Engineering

Brown University engineering alumni H. David Hibbitt Ph.D. ’72 and Enrique Lavernia ’82 have been elected to the National Academy of Engineering (NAE). Hibbitt, founder and retired chairman of ABAQUS Inc. (now known as Dassault Systèmes Simulia Corp.), was honored for creation and development of the ABAQUS finite element code for nonlinear structural analysis and its worldwide dissemination. He is one of 11 new foreign associates elected.

“I have been truly fortunate in having so many talented colleagues who chose to join our efforts, so I view this award as coming to me as the representative of that team,” said Hibbitt. “It is a great honor for us all. It is the outcome of work by an amazingly strong team of applied mechanics people, mathematicians, and computer scientists, all working together to deliver the Abaqus software suite. Several others in that team also came from Brown Engineering, including Paul Sorensen ’71 Sc.M.’75 Ph.D.’77, Joop Nagtegaal Ph.D. ’73, David Berman ’84 Sc.M.’85, Mark Bohm ’84, and David Reynolds Sc.M.’91 Ph.D.’93.”

Lavernia, Dean of the College of Engineering, and Distinguished Professor of Chemical Engineering and Materials Science at University of California, Davis, was recognized for contributions to novel processing of metals and alloys, and for leadership in engineering education. He is one of 69 new members elected. The total U.S. membership is now 2,250 members and the number of foreign associates is now 211.

“This is a spectacular achievement for David and Enrique and we are extremely happy for them,” said Dean Larry Larson. “To have two alumni elected in one year from Brown is a wonderful accomplishment.”

Maurice Herlihy, professor of computer science at Brown, was also elected to the NAE this year for concurrent computing techniques for linearizability, non-blocking data structures, and transactional memory.

Michael Ortiz, who was a professor at Brown from 1984-1995 and is now a professor at California Institute of Technology, was elected for contributions to computational mechanics to advance the underpinnings of solid mechanics.

Election to the National Academy of Engineering is among the highest professional distinctions accorded to an engineer. Academy membership honors those who have made outstanding contributions to “engineering research, practice, or education, including, where appropriate, significant contributions to the engineering literature,” and to the “pioneering of new and developing fields of technology, making major advancements in traditional fields of engineering, or developing/implementing innovative approaches to engineering education.”

Hibbitt and Lavernia join an exclusive group of 12 Brown engineering alumni already in the NAE that includes: Walter J. Weber ’56 (elected 1985), William F. Allen ’41 (elected 1986), T. Dixon Dudderar PhD’66 (elected 1992), Wai-Fah Chen PhD’66 (elected 1995), George J. Dvorak (elected 1995), Marc S. Newkirk ’69 (elected 1997), Hratch Gregory Semerjian Sc.M.’68 Ph.D.’72 (elected 2000), Chain T. Liu Sc.M.’64 Ph.D.’67 (elected 2004), Robert M. McMeeking PhD’75 (elected 2005), Jean-Yves Parlange Ph.D.’62 (elected 2006), Alan I. Taub ’76 (elected 2006), and Ares J. Rosakis ScM’80 PhD’83 (elected 2011).

Ten current or former Brown engineering faculty members have been elected to the National Academy of Engineering, including Huajian Gao, Walter H. Annenberg Professor of Engineering, who was elected in 2012. Other members include: Vice President for Research and Otis Randall University Professor Clyde Briant (elected 2010), Subra Suresh (elected 2002), Professor Emeritus Alan Needleman (elected 2000), Professor Emeritus L.B. Freund (elected 1994), Rush C. Hawkins University Professor Rod Clifton (elected 1989), Joseph Kestin (elected 1982), James R. Rice (elected 1980), Daniel C. Drucker (elected 1967), and William Prager (elected 1965).

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Robert Rome Named Associate Dean for Development and Planning at Brown University School of Engineering

Robert Rome has been named to the newly created position of associate dean for development and planning at the School of Engineering at Brown University. Rome began his duties on February 4 and is responsible for development of expanded master’s programs, growth of industry connections, planning for space growth of the School, communications, development, and diversity initiatives.

Rome comes to College Hill from the University of California San Diego, where he was the chief operations officer of the Department of Electrical and Computer Engineering. He brings a wealth of experience in development, student affairs, graduate program development, and financial management.

Rome holds a bachelor’s degree in psychology from American University and a master’s degree in education from the University of Pennsylvania.

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A better way to culture central nervous cells

A protein associated with neuron damage in Alzheimer's patients provides a superior scaffold for growing central nervous system cells in the lab. The findings could have clinical implications for producing neural implants and offers new insights on the complex link between the apoE4 apolipoprotein and Alzheimer's disease. Results appear in the journal Biomaterials.

PROVIDENCE, R.I. [Brown University] — A protein associated with neuron damage in people with Alzheimer’s disease is surprisingly useful in promoting neuron growth in the lab, according to a new study by engineering researchers at Brown University. The findings, in press at the journal Biomaterials, suggest a better method of growing neurons outside the body that might then be implanted to treat people with neurodegenerative diseases.

A more dependable scaffold for neural cell culture
Rat central nervous system cells cultured in the apoE4
protein (right) fare better, with more axons and dendrites
than cells cultured in laminin (left). Ironically, apoE4 is
associated with the neural deficits of Alzheimer's disease
in the body. Credit: Palmore Lab/Brown University

The research compared the effects of two proteins that can be used as an artificial scaffold for growing neurons (nerve cells) from the central nervous system. The study found that central nervous system neurons from rats cultured in apolipoprotein E-4 (apoE4) grew better than neurons cultured in laminin, which had been considered the gold standard for growing mammalian neurons in the lab.

“Most scientists assumed that laminin was the best protein for growing CNS (central nervous system),” said Kwang-Min Kim, a biomedical engineering graduate student at Brown University and lead author of the study, “but we demonstrated that apoE4 has substantially better performance for mammalian CNS neurons.”

Kim performed the research under the direction of Tayhas Palmore, professor of engineering and medical science and Kim’s Ph.D. adviser. Also involved in the project was Janice Vicenty, an undergraduate from the University of Puerto Rico, who was working in the Palmore lab as a summer research fellow through the Leadership Alliance.

One size doesn't fit all
Tayhas Palmore and Kwang-Min Kim showed that lamnin,
the preferred scaffold for peripheral nerve cells, is not the
best choice for culturing cells from the central nervous
system. The protein apoE4 works much better.
Credit: Mike Cohea/Brown University

The results are surprising partly because of the association of apoE4 with Alzheimer’s. Apolipoproteins are responsible for distributing and depositing cholesterols and other lipids in the brain. They come in three varieties: apoE2, apoE3 and apoE4. People with the gene that produces apoE4 are at higher risk for amyloid plaques and neurofibrillary tangles, the hallmarks of Alzheimer’s. But exactly how the protein itself contributes to Alzheimer’s is not known.

This study suggests that outside the body, where the protein can be separated from the cholesterols it normally carries, apoE4 is actually beneficial in promoting neuron growth.


Growing new neurons
In the body, neurons grow in what’s called an extracellular matrix (ECM), a protein-rich scaffold that provides cells with nutrients and a molecular structure in which to grow. To grow neurons in the lab, scientists try to mimic the ECM present in the body. Laminin is a common protein in the body’s ECM, and studies have shown that laminin aids the growth of neurons from the peripheral nervous system (nerve cells that grow outside the brain and spinal cord).

It was largely assumed, Kim said, that because laminin was good for growing peripheral nerve cells, it would also be good for growing central nerve cells. That turns out not to be the case.

Kim was inspired to test the effects of apoE4 by a previous study that found that a mixture of apoE4 and laminin promoted CNS cell growth better than laminin alone. “The previous work hadn’t tested the effects apoE4 by itself,” Kim said. “So we started working on a side-by-side comparison of apoE4 and laminin.”

Kim and his colleagues cultured rat hippocampal cells — a model for mammalian CNS neurons — in four different treatments: laminin, laminin and apoE4 mixed, apoE4 alone, and bare glass. They found that cells cultured in apoE4 alone performed substantially better than any other treatment. The apoE4 cells were more likely to adhere to the protein scaffold, which is necessary for proper growth. They also showed more robust growth of axons and dendrites, the wire-like appendages that enable neurons to send and receive nerve signals.

Laminin doesn’t seem to be of much benefit at all for culturing CNS cells, according to the study. Cells cultured on laminin alone did not perform any better than cells cultured on bare glass.

That was another big surprise, Kim said, because laminin is so widely used in all kinds of neuron cultures.

A second part of the research looked at the chemical pathways through which proteins may enhance neuron growth. Previous work had found two neuron receptors, the gateways through which neurons interact with the outside world, that play a role in how external proteins trigger cell growth. However, when Kim blocked these two receptors, known as integrin and HSPG, he found that apoE4 still enhanced neuron growth. That finding suggests that neurons use an as yet unknown pathway to interact with apoE4.

“This discovery opens up a new target for researchers who are interested in identifying receptors that are important for spurring neural growth,” Palmore said.

Application to neural prosthetics
Unlike other cells in the body, nerve cells tend not to regenerate after being damaged by disease or trauma. So researchers hope that they can eventually implant lab-grown cells in the body to treat trauma or neurodegenerative diseases like Alzheimer’s.

“People are looking at all these different proteins to see if we can make a material — a scaffold — that to a neuron, looks and feels like their natural environment,” said Palmore. “The finding that apoE4 is a better protein to add to neural scaffolds is a good breakthrough because most people have been using laminin for the central nervous system models, which turns out to be less than optimal.”

The research was supported by the National Science Foundation (HRD-0548311) and the National Institutes of Health.

- by Kevin Stacey

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Brown Engineering Student Cory Hargus Wins Award at National Collegiate Research Conference

Brown engineering student Cory Hargus ’13.5 has won an Award of Excellence and a $250 prize at the second annual National Collegiate Research Conference at Harvard on January 26, 2013. He entered the poster presentation competition with his research titled, “Solar Enriched Biofuels Via Oxidizable Metal Catalysts.” Hargus was one of more than 200 students entering the poster competition.

A biomedical engineering concentrator, Hargus is a member of the AIChE (American Institute of Chemical Engineers) student group at Brown and a research assistant in the Peterson Catalyst Lab.

“Since the day he joined our group, Cory has continued to surprise me with the level of sophistication he employs in his research,” said Andrew Peterson, assistant professor of engineering. “He started this work as a 'side project' while he helped with experimental work, but he quickly broadened it into a sophisticated and innovative analysis, teaching himself the key concepts in thermodynamics and electronic structure he needed to succeed. The recognition he received in Cambridge this weekend is well-deserved.”

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Brown/RISD/Erfurt Team Selected to Compete in 2014 Solar Decathlon Europe

Team Inside Out, composed of students from Brown University, Rhode Island School of Design and University of Applied Sciences of Erfurt (Germany), has been selected to compete in the Solar Decathlon Europe 2014 competition. The Brown/RISD/Erfurt team is one of only 20 teams from 16 countries selected to participate in the international competition which will be held in Versailles, France, in June-July 2014.

These 20 teams now have 18 months to work on the design, production and implementation of their respective projects, to be assembled and presented in Versailles. The teams will have to meet the challenge of fully designing and constructing an energy independent solar house.

The Solar Decathlon team brings together a diverse group of participants from Brown, RISD and Erfurt. Its evolution goes can be traced to Jonathan Knowles, professor of architecture at RISD, who led the RISD Solar Decathlon team in the 2005 edition of the competition. His positive experience in 2005 inspired him to start building the current team. The University of Applied Sciences of Erfurt was a natural partner for several reasons, including Prof. Knowles’ longstanding collaboration with Prof. Rolf Gruber, Erfurt’s expertise in passive architecture, and Erfurt’s proximity to the 2014 Solar Decathlon competition site in Versailles.

“Brown University offers talented students and strength in science and engineering that will help develop the project’s technical innovations that are an important component of the competition,” said Derek Stein, assistant professor of physics and the faculty liaison for the team.

The Solar Decathlon core team members from Brown include engineering students Matt Breuer ’14, Montana Feiger ’14, Isby Lubin ’16, Beverly Xu ’14, and Gareth Rose ’16 in addition to Howard Carter ’16, Jonah Fay ’12.5, Sage Green ’14, and Haily Tran ’16.

The students have already developed the project’s concept of a “woven” house, whose reconfigurable walls will be made of textiles, and whose various uses will be intertwined with the needs of the community. The team is rethinking what materials can go into energy and cost-efficient housing, as well as what designs will promote efficient interactions between people and their environment.

“We are designing the house to have impacts beyond its walls; users will interact with elements of the house playfully, and we will design positive feedbacks to teach users about sustainability best practices,” said Breuer. “As part of this, we are weaving the systems that are traditionally kept in the background into the foreground - users will be aware of the presence of electrical, heating, and water systems and how their behavior impacts their resource consumption. We hope this will strengthen the relationship that users have with their living space and will promote a responsible and environmentally friendly lifestyle.”

About Solar Decathlon
The Solar Decathlon is an international competition organized every other year by the Department of Energy (DOE) in the United States. Since 2010, a Solar Decathlon has been organized in Europe in the alternating years between the American competitions. The first two European competitions were held in Madrid. The next competition, to be held in June/July 2014, is being organized by France and will take place in Versailles. A competition will also be held in 2013 in the United States and China.

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Professor Nitin Padture Honored by IIT Bombay

Nitin Padture, professor of engineering and director of the Center for Advanced Materials Research at Brown University, received a Distinguished Service Award from his undergraduate alma mater, the Indian Institute of Technology in Bombay. Since 1999 the awards have been given to IIT Bombay alumni who have contributed in a notable and sustained manner to the progress of the Institute.

Padture was honored as the co-leader of the Class of 1985 Legacy Projects, which include promoting entrepreneurship, supporting recruitment of top junior faculty at IITB, and supporting a Faculty Wellness Fund to benefit retired IITB faculty members and their families lacking medical coverage. Padture received the award last month at IITB’s alumni day.

Padture's research and teaching interests are in the broad areas of synthesis/processing and properties of advanced materials used in applications ranging from jet engines to solar cells to computer chips, impacting transportation, energy, and information technology sectors. He has published 125 journal papers, which have been cited over 5,000 times, is co-inventor of four patents, and he has delivered over 150 invited/keynote/plenary talks in the U.S. and abroad. Padture is the recipient of several awards and is Fellow of the American Ceramic Society and Fellow of the American Association for the Advancement of Science. He is editor of a prominent international journal, Scripta Materialia.

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