Stanford making robots feel
Engineers are developing an artificial nervous system that could give robots reflexes and the ability to sense touch.
The artificial sensory nerve system can activate the twitch reflex in a cockroach and identify letters in the Braille alphabet.
It is an important step toward creating artificial skin for prosthetic limbs, to restore sensation to amputees and, perhaps, one day give robots some type of reflex capability.
“We take skin for granted but it’s a complex sensing, signaling and decision-making system,” said Zhenan Bao, a professor of chemical engineering at Stanford University.
“This artificial sensory nerve system is a step toward making skin-like sensory neural networks for all sorts of applications.”
The researchers constructed an artificial sensory nerve circuit that could be embedded in a future skin-like covering for neuro-prosthetic devices and soft robotics.
The nerve circuit brings together three existing components.
The first is a touch sensor that can detect minuscule forces. This sensor sends signals through the second component – a flexible electronic neuron. The touch sensor and electronic neuron are improved versions of inventions previously reported by the Bao lab.
Sensory signals from these components stimulate the third component, an artificial synaptic transistor modelled after human synapses.
In humans, when a sudden tap causes the knee muscles to stretch, certain sensors in those muscles send an impulse through a neuron. The neuron in turn sends a series of signals to the relevant synapses. The synaptic network recognizes the pattern of the sudden stretch and emits two signals simultaneously, one causing the knee muscles to contract reflexively and a second, less urgent signal to register the sensation in the brain.
“Biological synapses can relay signals, and also store information to make simple decisions,” said Tae-Woo Lee of Seoul National University, who spent his sabbatical year in Bao’s Stanford lab to initiate the collaborative work.
“The synaptic transistor performs these functions in the artificial nerve circuit.”
In one test they hooked up their artificial nerve to a cockroach leg and applied tiny increments of pressure to their touch sensor.
The electronic neuron converted the sensor signal into digital signals and relayed them through the synaptic transistor, causing the leg to twitch more or less vigorously as the pressure on the touch sensor increased or decreased.
They also showed that the artificial nerve could detect various touch sensations. In one experiment the artificial nerve was able to differentiate Braille letters. In another, they rolled a cylinder over the sensor in different directions and accurately detected the direction of the motion.
The group also hopes to create low-power, artificial sensor nets to cover robots, the idea being to make them more agile by providing some of the same feedback that humans derive from their skin.