Plastic Gets Pavlovian Walking and Grasping Skills in New Functional Materials Experiment

Tiny, snail-like "actuators" are taught to associate light with heat in a novel twist on Pavlovian conditioning.

Gareth Halfacree
4 years agoRobotics
The team's experiment was based on Pavlov's Dog. (📷: Priimägi et al)

Researchers from Tampere University and Aalto University in Finland are teaching plastic a new trick, courtesy of Pavlovian conditioning: Walking and grasping under the command of light, marking the first time a synthetic actuator has been "taught" to move without a controlling computer.

"Our research is essentially asking the question if an inanimate material can somehow learn in a very simplistic sense," explains senior author Arri Priimägi of his team's work. "My colleague, Professor Olli Ikkala from Aalto University, posed the question: Can materials learn, and what does it mean if materials would learn? We then joined forces in this research to make robots that would somehow learn new tricks."

The result is a "conditioned" plastic, constructed of liquid crystal polymer networks and a coat of dye, formed into a soft actuator capable of converting energy into mechanical motion. The "learning" part of the process: Initially the actuator responds only to heat, but by "teaching" it to associate light with heat it begins to respond to light as well — at least enough to move at around 1mm per second, keeping rough pace with the average garden snail.

"At first, the liquid crystal polymer did not react to light at all, but during the process, it learned to move and grab objects under the guidance of light," co-author Ikkala explains. "The idea is the same as in [our] previous study, but now the conditioning includes tangible functions."

"This study that we did was inspired by Pavlov's dog experiment," claims Priimägi, referring to the classic conditioning experiments by Ivan Pavlov in which a dog was taught to salivate upon hearing a bell. "If you think about our system, heat corresponds to the food, and the light would correspond to the bell in Pavlov's experiment.

"Many will say that we are pushing this analogy too far," Priimägi admits. "In some sense, those people are right because compared to biological systems, the material we studied is very simple and limited. But under right circumstances, the analogy holds."

The secret sauce lies in the dye, which isn't merely an aesthetic add-on. "For material to learn, it must have a memory. When the material is heated, the dye originally spread on the surface of the liquid crystal polymer penetrates into the material, thus forming the memory," Ikkala explains. "Different dyes react to different wavelengths of light, so the initially neutral stimulus (colour of light) can be controlled by the dye applied onto it. Additionally, when designing the material, molecules must be positioned so that the material reacts as desired when heated."

The team has indicated it will continue to investigate these memory functions, seeing if it's possible to construct functional material which respond to other stimuli including electric fields, magnetism, changes in humidity, or particular chemicals, as well as whether the materials can be conditioned using entirely separate stimuli.

The research has been published in the journal Matter under open access terms.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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