October 26, 2009
Just by a Whisker
>From rats to robots: The story of the humble whisker
The excitement builds ...
The cameras are ready to roll ...
The lights ... ready to shine ...
And the talent is ready for her close-up ...
The movie star is a rat!
Nearby, robotic devices and robotic parts are scattered about, some looking like props from a science fiction movie.
But this isn't anything even close to a movie set. It's the Hartmann Lab at Northwestern University, just outside of Chicago. And the science going on here is quite real. It's a place where biology and engineering seem to cross paths. It's all part of research that originates from one question.
"The big question that our laboratory is interested in is how do animals, including humans, manage to go and gather sensory data from the world and somehow turn that into a perception of the world," says Mitra Hartmann, associate professor at Northwestern's McCormick School of Engineering.
With funding from the National Science Foundation (NSF), Hartmann and her students are beginning to get a feel for how animals perceive the world around them. The team starts by looking at one of the most powerful sensory systems in nature: the rat whisker system.
Feeling the way
"Rats use their whiskers in a manner quite similar to the way that humans use their hands to explore different objects," says Hartmann.
High speed imagery is the best way for Hartmann's team to capture the motion of whiskers, which can move back and forth, or whisk, up to 25 times a second. Rats can not see detail with their eyes. So they are equipped with two sets of 30 whiskers each that help them sense the world around them.
As a rat whisker encounters an object, the object causes the whisker to bend. Those forces and movements are sensed by nerves located in a follicle at the base of the whisker and are sent to the brain for interpretation.
Hartmann says, "Using their whiskers, rats can figure out an object's shape, size, orientation or texture. There was one study that suggested that rats are able to do texture discriminations as well as you can do with your fingertips. So they are really very sensitive."
One of the questions Hartmann's team is focusing on right now is how rats interpret shapes. Biomedical engineering student Blythe Towal uses laser technology to shed new light on how rats' head and whisker movements might change as they explore different shapes. The laser light helps the researchers see the fine detail of each individual whisker's movement. Ultimately, the scientists aim to compare that data with electrical signals from the rat's brain to better understand how rats perceive the object they are exploring.
Hartmann and her team take what they learn about perception in animals to look at ways they might create artificial sensing. That's the engineering part of our story.
Just a stone's throw from the where the rats are photographed, a Chia Pet® sculpture in the form of a head is being checked out by a set of artificial wire whiskers. The whiskers come complete with sensors that send information about their forces and movements to a computer.
Biomedical engineering student Chris Schroeder is exploring prediction. For example, if you put your hands along a curved wall in the dark, you can predict the continuing shape of that wall. Chris is having artificial whiskers run along curved objects. Using data from the whiskers, the computer can predict to Schroeder how the curve of an object will continue.
"We can sweep the whisker along the object and we can extract the object's contour continuously as we are sweeping the whisker along." The computer can draw a 3-D image of what the whiskers are sensing.
New types of sensors
Hartmann believes the incremental steps her team is making towards understanding perception will lead to some revolutionary technologies. One application that others have raised is that planetary rovers might one day come complete with a set of whiskers to give precise details about a planet's surface. Other robots like bomb detection devices might use whiskers to survey dark areas.
"Cameras don't work in the dark unless you have an extra light source, and they can be confused by glare or reflections or fog. So you can certainly imagine whiskers on an autonomous navigation system to explore the world in a way that cameras couldn't do."
Hartmann also envisions prosthetic devices such as artificial limbs that move based on how they sense the world around them. She admits those breakthroughs are far off. Until then, she and her team are forging a new path of research: discovering what they can about biology, to help advance technology.
Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.