We report electrically shielded capacitive stretchable force sensors, that simultaneously measure normal and shear strains, even near electric sparks. The device consists of an outer conductive stretchable shielding layer (carbon-loaded silicone) and a central silicone layer with embedded air channels and three liquid metal electrodes. We report sub-mN force resolution in both normal and shear directions, can measure forces larger than 10 N, and operate reliably after repeated loading to 20 N load. Performance is unaffected by nearby high DC and AC electric fields, allowing use in a wide range of robotic sensing applications.
We present fully-printed, stretchable, hydraulically-amplified mm-scale zipping electrostatic actuators for both quasi static and high frequency actuation. Inkjet printing of silicones, stretchable conductors and sacrificial materials enables high design flexibility of both actuators and array configurations. The 5 mm wide actuators generate displacement and forces well above haptic perception threshold values from DC to 200 Hz, as shown with user tests. Parallel fluid filling combined with independent sealing of each pouch enables arrays of self-contained fluidic actuators with no cross-talk. This work enables customizable wearables for realistic cutaneous haptic feedback.
Zipping electrostatic actuators operate by bending flexible electrodes using electrostatic forces. This principle allows the use of a wide range of dielectric and conductive materials. Additive Manufacturing (AM) techniques can be used to fabricate these actuators. The selective direct deposition of multiple materials improves the actuator design flexibility, as customized prototypes can be fabricated without masks and moulds. Here we present the first integration of AM techniques in the fabrication process of Hydraulically Amplified Taxels (HAXELs), a class of electrostatic actuators combining zipping electrodes deformation with the inflation of a stretchable material using fluidic coupling. We use an inkjet printer (jetlab® 4 by MicroFab) to deposit Polydimethylsiloxane (PDMS) as the stretchable material and Ethyl Cellulose as a sacrificial material for fluidic features patterning. We integrate gold-sputtered, laser-cut Mylar foils for the flexible part of the actuator by encapsulating them between the inkjet-printed layers. After dissolving the sacrificial material, a dielectric fluid can be injected in the fabricated actuators. Qualitative evaluation of a fabricated device is reported, showing electrode zipping. The presented fabrication process allows future fabrication of highly integrated actuators having arbitrary shapes.
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