Stretchy Wearable Patch Allows Two-Way Communication With Robots

Multifunctional metal-oxide semiconductor used to build flexible RRAM, transistors, and sensors

2 min read
A stretchy, wearable patch on a human hand (right) controls a robot hand (left).
Gif: Cunjiang Yu/IEEE Spectrum

Engineers at the University of Houston are trying to make the melding of humans and machines a little easier on the humans. They’ve developed an easy-to-manufacture flexible electronics patch that, when attached to a human, translates the person’s motion and other commands to a robot and receives temperature feedback from the robot.

Led by University of Houston assistant professor Cunjiang Yu, the team developed transistors, RRAM memory cells, strain sensors, UV-light detectors, temperature sensors, and heaters all using the same set of materials in a low-temperature manufacturing process. They integrated the different devices into a 4-micrometer-thick adhesive plastic patch.

A paper describing the Houston researchers’ work appears this week in Science Advances.

With the patch on the back of a volunteer’s hand, the researchers were able to control a robot hand—causing it to close or open according to what the human’s hand motion did to the patch’s strain sensors. What’s more, they were able to close the human-robot control loop by providing temperature feedback from the robotic hand to the human one using the patch’s integrated heater circuits.

University of Houston engineers integrated several types of indium zinc oxide-based devices including (left to right): RRAM, FET, UV sensor, temperature sensor, and strain sensor.University of Houston engineers integrated several types of indium zinc oxide-based devices including (left to right): RRAM, FET, UV sensor, temperature sensor, and a strain sensor.Images: Cunjiang Yu

The devices are all structures patterned using photolithography and are made up of 50-nanometer-thick gold conductors, indium zinc oxide (IZO) semiconductor, polyimide encapsulation, and (for the transistors) a common dielectric epoxy called SU-8. The conductors’ serpentine shape allows the devices to stretch with the polymide without breaking, but it’s the semiconductor’s versatility that is the real star of the show.

IZO acts as an electron-conducting semiconductor in the transistors and a photoconductor in the UV sensors. IZO’s resistance decreases with temperature, so it could act as a variable resistor in the temperature sensor (thermistor); its resistance increases with strain, so it can form a strain sensor. And in yet another structural arrangement of these materials, certain voltages will form or break conductive filaments in the IZO, yielding nonvolatile resistive memory (RRAM). The IZO maintains all this functionality even after being deposited as a colloid and drying to form a gel, a so-called sol-gel process.

“It’s quite astonishing,” says Yu. “Traditionally, to achieve multiple functions you might need the heterogeneous integration of materials, or multiple chips together. But now using one material you can do all this.”

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The Bionic-Hand Arms Race

The prosthetics industry is too focused on high-tech limbs that are complicated, costly, and often impractical

12 min read
A photograph of a young woman with brown eyes and neck length hair dyed rose gold sits at a white table. In one hand she holds a carbon fiber robotic arm and hand. Her other arm ends near her elbow. Her short sleeve shirt has a pattern on it of illustrated hands.

The author, Britt Young, holding her Ottobock bebionic bionic arm.

Gabriela Hasbun. Makeup: Maria Nguyen for MAC cosmetics; Hair: Joan Laqui for Living Proof

In Jules Verne’s 1865 novel From the Earth to the Moon, members of the fictitious Baltimore Gun Club, all disabled Civil War veterans, restlessly search for a new enemy to conquer. They had spent the war innovating new, deadlier weaponry. By the war’s end, with “not quite one arm between four persons, and exactly two legs between six,” these self-taught amputee-weaponsmiths decide to repurpose their skills toward a new projectile: a rocket ship.

The story of the Baltimore Gun Club propelling themselves to the moon is about the extraordinary masculine power of the veteran, who doesn’t simply “overcome” his disability; he derives power and ambition from it. Their “crutches, wooden legs, artificial arms, steel hooks, caoutchouc [rubber] jaws, silver craniums [and] platinum noses” don’t play leading roles in their personalities—they are merely tools on their bodies. These piecemeal men are unlikely crusaders of invention with an even more unlikely mission. And yet who better to design the next great leap in technology than men remade by technology themselves?

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