Flexible haptics patch senses pressure too: Page 2 of 2

June 14, 2019 //By Julien Happich
Using readily available flexible foil materials, researchers from the University of California, Berkeley, have designed an ultra-thin haptics film capable of strong actuations but also suitable as a pressure sensor.

The equivalent piezoelectric coefficient of such a piezoelectret device (d33 value) was characterized to be 4050 pC/N, exceeding those of many traditional piezoelectric or piezoelectret materials or devices, meaning the soft actuator was able to produce a strong vibration force close to the vibration mode of a cell phone at 20mN. Meanwhile, the flexible pressure sensor part, operating without power, exhibited a minimum pressure detection limit of 1.84 Pa (the weight of dandelion seeds) with less than 1% readout variations for more than 6000 operations.

The sandwich-structured piezoelectret including two FEP layers on the top and bottom and a soft Ecoflex layer at the centre with circular-shape holes.

Power consumption for the prototype actuator was only 8.25mW under a driving input of 3.33V/μm, making the device suitable for low power wearables, whereas tapping the sensor with the fingertip generated enough charges to illuminate selected liquid crystal display pixels (showing the number of “1” in an experiment).

The researchers anticipate they could further optimize the geometry design of their sandwich-structured piezoelectret and its performances with other materials, possibly leading to large area actuator/sensor patches for practical mechanical human-machine interface applications.

Related article:

Thin flexible tactile actuator for wearable haptics

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