The flexible piezoelectret-based device is both a sensor and actuator that vibrates as feedback, similar to the way a smartphone vibrates when a user opens an app or makes a payment. The device, say the researchers, could eventually be used in clothes and other wearable technologies.
“There are many applications for this technology that can sense motion and give haptic feedback,” says Liwei Lin, mechanical engineering professor, co-director of the Berkeley Sensor & Actuator Center (BSAC) and one of the lead authors of a paper on the [project. “One application is AR/VR. Right now, if you are playing a game and hitting a wall, you only hear a sound. With our device, the sensor can detect if you are going to hit something, and the actuator can vibrate to simulate a physical impact.”
Because the vibrations generated can be customized, says Lin, this technology could also help people with visual or hearing impairments communicate with the world around them via vibrations.
“Our device is about 150 micrometers thick, similar to the diameter of human hair,” says Juwen Zhong, a postdoctoral researcher at BSAC and the other lead author on the paper. “Its flexibility and its ability to achieve both sensor and actuator functions is based on an innovative sandwich structure that harnesses piezoelectricity.”
The outside layers of the sandwich structure consist of fluorinated ethylene propylene elect films while the middle layer is an Ecoflex spacer, coated with gold aluminum electrodes on top and aluminum electrodes on the bottom. Under mechanical deformation caused by human movement, the sensor function of the device can generate electrical outputs without a power supply. These electrical outputs can then help turn on the actuator via electrostatic force to generate vibrations that can be felt by human skin.
Currently, say the researchers, the device’s actuating mode can generate up to 20 meganewtons – comparable to the vibrations of a cellphone – and can sense objects as light as a dandelion seed. The device is claimed to outperform popular piezoelectric materials, with the technology showing a high piezoelectric coefficient and low driving voltage, which is key to enhancing the sensor’s sensitivity and the amount of electricity needed to power the actuator.
Looking ahead, the researchers say they would like to make a patch prototype with more of these piezoelectric “pixels.” Their current prototype has nine pixels; adding more would allow them to generate vibrations that mimic different textures. They also hope to bring down the voltage required to power this device so that it can be easily powered.
“In the future, this sensor-actuator patch could potentially be made in the form of gloves and suits that provide touch feeling for immersion virtual experiences,” says Zhong. “So if you are on the West Coast and your mom is on the East Coast, and you are both wearing devices based on this technology, the sensors can sense that if you are making a hugging motion and the actuators will make you feel like you are hugging.”
Wearable e-skin sensor promises accurate voice recognition
Wearable haptics push boundaries for gamers
Graphene-based e-skin detects vibrations from audio to ultrasound
Flexible tactile actuator holds promise for wearable haptics