Eric Sembrat's Test Bonanza

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Prof. Goldman’s recent work on snake locomotion on granular media published in Science and discussed in the NY Times.

Monday, October 13, 2014
Summary: 

Prof. Goldman’s recent work on snake locomotion on granular media published in Science and discussed in the NY Times.

Intro: 

Prof. Goldman’s recent work on snake locomotion on granular media published in Science and discussed in the NY Times.

Alumni: 

Snakes and snake-like robots show how sidewinders conquer sandy slopes

Thursday, October 9, 2014

The amazing ability of sidewinder snakes to quickly climb sandy slopes was once something biologists only vaguely understood and roboticists only dreamed of replicating. By studying the snakes in a unique bed of inclined sand and using a snake-like robot to test ideas spawned by observing the real animals, both biologists and roboticists have now gained long-sought insights.

In a study published in the October 10 issue of the journal Science, researchers from the Georgia Institute of Technology, Carnegie Mellon University, Oregon State University, and Zoo Atlanta report that sidewinders improve their ability to traverse sandy slopes by simply increasing the amount of their body area in contact with the granular surfaces they’re climbing.

As part of the study, the principles used by the sidewinders to gracefully climb sand dunes were tested using a modular snake robot developed at Carnegie Mellon. Before the study, the snake robot could use one component of sidewinding motion to move across level ground, but was unable to climb the inclined sand trackway the real snakes could readily ascend. In a real-world application – an archaeological mission in Red Sea caves – sandy inclines were especially challenging to the robot.

However, when the robot was programmed with the unique wave motion discovered in the sidewinders, it was able to climb slopes that had previously been unattainable. The research was funded by the National Science Foundation, the Army Research Office, and the Army Research Laboratory.

“Our initial idea was to use the robot as a physical model to learn what the snakes experienced,” said Daniel Goldman, an associate professor in Georgia Tech’s School of Physics. “By studying the animal and the physical model simultaneously, we learned important general principles that allowed us to not only understand the animal, but also to improve the robot.”

The detailed study showed that both horizontal and vertical motion had to be understood and then replicated on the snake-like robot for it to be useful on sloping sand.

“Think of the motion as an elliptical cylinder enveloped by a revolving tread, similar to that of a tank,” said Howie Choset, a Carnegie Mellon professor of robotics. “As the tread circulates around the cylinder, it is constantly placing itself down in front of the direction of motion and picking itself up in the back. The snake lifts some body segments while others remain on the ground, and as the slope increases, the cross section of the cylinder flattens.”

At Zoo Atlanta, the researchers observed several sidewinders as they moved in a large enclosure containing sand from the Arizona desert where the snakes live. The enclosure could be raised to create different angles in the sand, and air could be blown into the chamber from below, smoothing the sand after each snake was studied. Motion of the snakes was recorded using high-speed video cameras which helped the researchers understand how the animals were moving their bodies.

“We realized that the sidewinder snakes use a template for climbing on sand, two orthogonal waves that they can control independently,” said Hamid Marvi, a postdoctoral fellow at Carnegie Mellon who conducted the experiments while he was a graduate student in the laboratory of David Hu, an associate professor in Georgia Tech’s School of Mechanical Engineering. “We used the snake robot to systematically study the failure modes in sidewinding. We learned there are three different failure regimes, which we can avoid by carefully adjusting the aspect ratio of the two waves, thus controlling the area of the body in contact with the sand.”

Limbless animals like snakes can readily move through a broad range of surfaces, making them attractive to robot designers.

"The snake is one of the most versatile of all land animals, and we want to capture what they can do," said Ross Hatton, an assistant professor of mechanical engineering at Oregon State University who has studied the mathematical complexities of snake motion, and how they might be applied to robots. "The desert sidewinder is really extraordinary, with perhaps the fastest and most efficient natural motion we've ever observed for a snake."

Many people dislike snakes, but in this study, the venomous animals were easy study subjects who provided knowledge that may one day benefit humans, noted Joe Mendelson, director of research at Zoo Atlanta.

“If a robot gets stuck in the sand, that’s a problem, especially if that sand happens to be on another planet,” he said. “Sidewinders never get stuck in the sand, so they are helping us create robots that can avoid getting stuck in the sand. These venomous snakes are offering something to humanity.”

The modular snake robot used in this study was specifically designed to pass horizontal and vertical waves through its body to move in three-dimensional spaces.  The robot is two inches in diameter and 37 inches long; its body consists of 16 joints, each joint arranged perpendicular to the previous one.  That allows it to assume a number of configurations and to move using a variety of gaits – some similar to those of a biological snake.

“This type of robot often is described as biologically inspired, but too often the inspiration doesn’t extend beyond a casual observation of the biological system,” Choset said. “In this study, we got biology and robotics, mediated by physics, to work together in a way not previously seen.”

Choset’s robots appear well suited for urban search-and-rescue operations in which robots need to make their way through the rubble of collapsed structures, as well as archaeological explorations. Able to readily move through pipes, the robots also have been tested to evaluate their potential for inspecting nuclear power plants from the inside out.

For Goldman’s team, the work builds on earlier research studying how turtle hatchlings, crabs, sandfish lizards, and other animals move about on complex surfaces such as sand, leaves, and loose material. The team tests what it learns from the animals on robots, often gaining additional insights into how the animals move.

“We are interested in how animals move on different types of granular and complex surfaces,” Goldman said. “The idea of moving on flowing materials like sand can be useful in a broad sense. This is one of the nicest examples of collaboration between biology and robotics.”

In addition to those already mentioned, co-authors included Chaohui Gong and Matthew Travers from Carnegie Mellon University; and Nick Gravish and Henry Astley from Georgia Tech.

This research was supported by the National Science Foundation under awards CMMI-1000389, PHY-0848894, PHY-1205878, and PHY-1150760; by the Army Research Office under grants W911NF-11-1-0514 and W911NF1310092; and by the Army Research Lab MAST CTA under grant W911NF-08-2-0004; and by the Elizabeth Smithgall Watts endowment at Georgia Tech. The opinions expressed are those of the authors and do not necessarily represent the official views of the sponsoring agencies.

CITATION: Hamidreza Marvi et al., “Sidewinding with minimal slip: snake and robot ascent of sandy slopes,” Science 2014).

Research News
Georgia Institute of Technology
177 North Avenue
Atlanta, Georgia  30332-0181  USA

Media Relations Contacts: John Toon (404-894-6986) (jtoon@gatech.edu) or Brett Israel (404-385-1933) (brett.israel@comm.gatech.edu).
Writers: John Toon, Georgia Tech/Byron Spice, Carnegie Mellon University

Media Contact: 

John Toon

Research News

jtoon@gatech.edu

(404) 894-6986

Summary: 

Researchers from Georgia Tech, Carnegie Mellon, Oregon State University, and Zoo Atlanta report that sidewinders improve their ability to traverse sandy slopes by simply increasing the amount of their body area in contact with the granular surfaces they’re climbing. They've put that knowledge to work helping a snake-like robot.

Intro: 

Researchers from Georgia Tech, Carnegie Mellon, Oregon State University, and Zoo Atlanta report that sidewinders improve their ability to traverse sandy slopes by simply increasing the amount of their body area in contact with the granular surfaces they’re climbing. They've put that knowledge to work helping a snake-like robot.

Alumni: 

Prof. Fernandez-Nieves explores how co-flowing liquids stabilize chaotic “whipping” in microfluidic jets

Thursday, September 18, 2014
Summary: 

Prof. Fernandez-Nieves explores how co-flowing liquids stabilize chaotic “whipping” in microfluidic jets

Intro: 

Prof. Fernandez-Nieves explores how co-flowing liquids stabilize chaotic “whipping” in microfluidic jets

Alumni: 

Co-flowing liquids can stabilize chaotic “whipping” in microfluidic jets

Monday, September 8, 2014

Industrial wet spinning processes produce fibers from polymers and other materials by using tiny needles to eject continuous jets of liquid precursors. The electrically charged liquids ejected from the needles normally exhibit a chaotic “whipping” structure as they enter a secondary liquid that surrounds the microscopic jets.

But the liquid jets sometimes form a helical wave. And that was intriguing to Alberto Fernandez-Nieves, an associate professor in the School of Physics at the Georgia Institute of Technology.

By controlling the viscosity and speed of the secondary liquid surrounding the jets, a research team led by Fernandez-Nieves has now figured out how to convert the standard chaotic waveform to the stable helical form. Based on theoretical modeling and experiments using a microfluidic device, the findings could help improve industrial processes that are used for fiber formation and electrospray.

The research, conducted in collaboration with the University of Seville in Spain, was supported by the National Science Foundation (NSF). It was reported Sept. 8, 2014, in the early online edition of the journal Proceedings of the National Academy of Sciences (PNAS).

“We are developing an understanding of the basic coupling between hydrodynamic and electric fields in these systems,” said Fernandez-Nieves. “The issue we examined is fundamental physics, but it could potentially lead to something more interesting in fiber generation through electro-spinning.”

In conventional industrial processes, tiny metal needles apply an electric field as they eject the polymer-containing solution. In the laboratory, the researchers used a glass-based microfluidic device to create the jets so they could more closely examine what was happening. Using a conductive liquid, ethylene glycol, allowed them to apply an electrical field to produce electrified jets.

“When you charge these polymer solutions, the jets themselves move out of axis, which creates a chaotic phenomenon known as whipping,” Fernandez-Nieves explained. “This off-axis movement causes the jet to abruptly move in all directions, and in the industrial world, all that motion seems to be beneficial from the standpoint of making thinner fibers.”

The researchers experimented with many variables as their liquid jets emerged into a co-flowing secondary liquid inside the microfluidic device. Those variables included the applied electrical field, the flow rate of the ejected liquid and the secondary liquid, the viscosities of the liquids, the needle diameters and the physical geometry of microfluidic device.

While producing a whipped jet in a viscous dielectric material – polydimethylsiloxane oil – the researchers were surprised to see the chaotic motion switch over to a steady-state helical structure.

“We were able to stabilize the structure associated with the whipping behavior and found that the stable structure is a helix with a conical shape,” said Fernandez-Nieves. “You can picture it as a conical envelope, and inside the envelope you have a helix. Once the viscosity of the outer liquid is sufficient, you stabilize the structure and get this beautiful helix.”

Georgia Tech postdoctoral fellow Josefa Guerrero used a high-speed, microscope-based video camera operating at 50,000 frames per second to study the waveforms emerging from the experimental jets, which were less than five microns in diameter. The video allowed precise examination of the waveforms produced when the liquid flowed out of the glass needle and into the second liquid flowing around it.

Working with collaborators Javier Rivero-Rodriguez and Miguel Perez-Saborid at the University of Seville, the Georgia Tech team – Fernandez-Nieves, Guerrero and former postdoctoral fellow Venkata R. Gundabala – used hydrodynamics theory to help understand what they were seeing experimentally.

“By developing the model, we were able to balance the importance of the different forces in the experiment,” explained Fernandez-Nieves. “The helix was part of the solutions in the model and it reproduced some aspects of the experimentally observed helices.”

Once the jets were stabilized by the viscous secondary liquid, the properties of the helix were controlled by the electrical charge. In the experiment, the researchers applied approximately 1,000 volts to generate the jets.

“We learned that the outer fluid plays a major role in stabilizing the structure of the jets,” Fernandez-Nieves added. “Once the structure is stable, the details of the properties of the helical structure depend on the charge.”

Ultimately, the stable jets break up into spherical droplets. The researchers have not yet formed fibers with their experimental setup.

In future work, Fernandez-Nieves hopes to study other waveforms that may be produced by the system, and evaluate how controlling the liquid jets could improve industrial techniques used in fiber production and electrospray processes that generate clouds of droplets.

“We are interested in trying to map out those different behaviors,” he said. “For us as physicists, this is interesting because it allows us to explore, address and measure things that nobody could look at before in the way we can today. We are anxious to understand the applied impact.”

CITATION: Josefa Guerrero, et al., “Whipping of electrified jets,” Proceedings of the National Academy of Sciences, 2014.

This research was funded by the National Science Foundation (NSF) under award CBET-0967293. Any opinions expressed are those of the authors and do not necessarily reflect the officials views of the National Science Foundation.

Research News
Georgia Institute of Technology
177 North Avenue
Atlanta, Georgia  30332-0181  USA

Media Relations Assistance: John Toon (jtoon@gatech.edu) (404-894-6986) or Brett Israel (brett.israel@comm.gatech.edu) (404-385-1933).

Writer: John Toon

Media Contact: 

John Toon

Research News

jtoon@gatech.edu

(404) 894-6986

Summary: 

Industrial wet spinning processes produce fibers from polymers and other materials by using tiny needles to eject continuous jets of liquid precursors. The electrically charged liquids ejected from the needles normally exhibit a chaotic “whipping” structure as they enter a secondary liquid that surrounds the microscopic jets. A research team has now figured out how to convert the standard chaotic waveform to a stable helical form.

Intro: 

Industrial wet spinning processes produce fibers from polymers and other materials by using tiny needles to eject continuous jets of liquid precursors. The electrically charged liquids ejected from the needles normally exhibit a chaotic “whipping” structure as they enter a secondary liquid that surrounds the microscopic jets. A research team has now figured out how to convert the standard chaotic waveform to a stable helical form.

Alumni: 

School of Physics congratulates Perrin Schiebel for receiving a 2014 National Defense Science and Engineering Graduate Fellowship, NDSEG.

Friday, May 16, 2014
Summary: 

School of Physics congratulates Perrin Schiebel

for receiving a 2014 National Defense Science

and Engineering Graduate Fellowship, NDSEG.

Intro: 

School of Physics congratulates Perrin Schiebel

for receiving a 2014 National Defense Science

and Engineering Graduate Fellowship, NDSEG.

Alumni: 

School of Physics congratulates Associate Professor Daniel Goldman for receiving the PECASE award in Washington, DC.

Monday, April 28, 2014
Summary: 

School of Physics congratulates Associate Professor Daniel Goldman for receiving the PECASE award in Washington, DC.

Intro: 

School of Physics congratulates Associate Professor Daniel Goldman for receiving the PECASE award in Washington, DC.

Alumni: 

School of Physics congratulates Associate Professor Daniel Goldman for receiving the PECASE award in Washington, DC.

Monday, April 28, 2014
Summary: 

School of Physics congratulates Associate Professor Daniel Goldman for receiving the PECASE award in Washington, DC.

Intro: 

School of Physics congratulates Associate Professor Daniel Goldman for receiving the PECASE award in Washington, DC.

Alumni: 

Congratulations to Ben McInroe for winning prize for the best UROP talk

Friday, April 25, 2014
Summary: 

Congratulations to Ben McInroe for winning prize for the best UROP talk

Intro: 

Congratulations to Ben McInroe for winning prize for the best UROP talk

Alumni: 

School of Physics, Undergraduate prize winners 2014

Friday, April 18, 2014
Summary: 

School of Physics, Undergraduate prize winners 2014

Intro: 

School of Physics, Undergraduate prize winners 2014

Alumni: 

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