Molding-Free Fully-Printed Flexible Tactile Sensors With Performance- Enhancing Microstructures

Flexible tactile sensors have attracted a lot of attention due to their potential applications in biomedical monitoring and electronic skins. In this paper, we propose and verify a molding-free full-printing method for such sensors using a single microelectronic printer. The sensors are capacitive or piezoresistive transduced, and they consist of two inkjet printed electrodes with direct-ink-writing (DIW) printed dielectric or conductive microstructures sandwiched in between. The complete printing process for one device, taking only several minutes with an additional couple of hours for curing, is extremely fast and low-price while also being highly reliable. The fabricated capacitive sensors mainly show two linear regimes of sensitivity, one as high as 1.0 kPa
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for a loaded pressure below 200 Pa, and the other much lower but for a wide pressure range up to 200 kPa. This performance results from careful optimization of the printing resolution and coverage ratio for the dielectric layer and is comparable to and with some parameters better than those related microstructured sensors of the same mechanism fabricated with slow and expensive molding processes. In addition, the piezoresistive sensors also prove the diversity of flexible devices that can be fabricated using the same process flow. Such sensors are harnessed to demonstrate their effectiveness in detecting both gentle and heavy contacts, and in artificial tactile feedback for robotics.