A sensor-packed electronic glove may give robots an increased sense of touch and dexterity, similar to humans, allowing them to work with delicate objects. Developed by Stanford engineers, the team was able to show a glove-wearing robotic hand manipulating both a raspberry and ping-pong ball without causing damage.
“This technology puts us on a path to one day giving robots the sort of sensing capabilities found in human skin,” says Zhenan Bao, project researcher and chemical engineer.
Human Inspiration
To create such a design, the team first examined how layers of human skin band together to grant us with high levels of sensitivity. Stimuli, such as heat and pressure, are detected by the sensors in our outer skin layers, which, for example, are found abound in our palms and fingers. These touch sensors work together with one of the skin’s sublayers known as the spinosum, which is bumpy in nature resembling a landscape of hills and valleys.
When humans lightly touch an object, the sensors situated near the spinosum’s hilltops are triggered, according to Stanford. However, if someone touches an object with force, the outer skin will dive down into the spinosum’s valleys, and thus, sends back touch sensations with increased intensity. This sublayer of skin also detects the pressure’s direction (shear force).
The robotic glove’s sensors drew upon these facets of the human design as inspiration.
“Each sensor on the fingertip of the robotic glove is made of three flexible layers that work in concert. The top and bottom layers are electrically active. The researchers laid a grid of electrical lines on each of the two facing surfaces, like rows in a field, and turned these rows perpendicular to each other to create a dense array of small sensing pixels. They also made the bottom layer bumpy like the spinosum,” according to Stanford.
The duty to separate the top and bottom layers of electrodes was delegated to a rubber insulator. According to Stanford, “that separation was critical, because electrodes that are close without touching can store electrical energy.” Stored energy increased when the robotic finger pressed down, which pushed the top layer of electrodes closer to the bottom layer.
Put to the Test
The layered sensor system was fastened to fingers on a rubber glove placed over a robotic hand. As seen in the gif above, the pre-programmed, glove-wearing hand was able to touch a berry sans injury. The video below also demonstrates the system safely moving a ping-pong ball, which uses a sensor to measure the correct shear force.
Potential applications, according to the researchers, vary from robot-assisted surgery to repetitive, delicate tasks, like lifting eggs off a conveyor belt and into a carton. However, the above goals require essential programming, and the team hopes to create a version that can automatically apply the right force levels. Future goals also involve embedding the sensors directly into the skin-like robotic hand covering.
“We can program a robotic hand to touch a raspberry without crushing it, but we’re a long way from being able to touch and detect that it is raspberry and enable the robot to pick it up,” says Bao.
To learn more, read the paper, “A hierarchically patterned, bioinspired e-skin able to detect the direction of applied pressure for robotics,” published in Science Robotics.