Multimode Hydraulically Amplified Electrostatic Actuators for Wearable Haptics

Abstract

The sense of touch is underused in today’s virtual reality systems due to lack of wearable, soft, mm‐scale transducers to generate dynamic mechanical stimulus on the skin. Extremely thin actuators combining both high force and large displacement are a long‐standing challenge in soft actuators. Sub‐mm thick flexible hydraulically amplified electrostatic actuators are reported here, capable of both out‐of‐plane and in‐plane motion, providing normal and shear forces to the user’s fingertip, hand, or arm. Each actuator consists of a fluid‐filled cavity whose shell is made of a metalized polyester boundary and a central elastomer region. When a voltage is applied to the annular electrodes, the fluid is rapidly forced into the stretchable region, forming a raised bump. A 6 mm × 6 mm × 0.8 mm actuator weighs 90 mg, and generates forces of over 300 mN, out‐of‐plane displacements of 500 µm (over 60% strain), and lateral motion of 760 µm. Response time is below 5 ms, for a specific power of 100 W kg−1. In user tests, human subjects distinguished normal and different 2‐axis shear forces with over 80% accuracy. A flexible 5 × 5 array is demonstrated, integrated in a haptic sleeve.

Intelligent Soft Surgical Robots for Next‐Generation Minimally Invasive Surgery

“…The surface texture, topography, stiffness, deformation, applied force, and other desired information of the internal organs of the patient can be measured and fed back by the integrated sensing system of the surgical tools and then transmitted to the surgeon through tactile reproduction provided by the soft actuator array. Some researches using soft robotic technologies for haptic feedback have emerged in recent years, and a recent review of them can be found in the study by Yin et al [408] Common haptic feedback methods based on mechanical stimulation include vibrotactile stimulation, [409,410] normal pressing, [411,412] and skin stretch, [413,414] and the introduction of soft technologies can achieve safe, compact, and lightweight system integration as well as good simulation of tactile sensation of soft organs.…”

Soft Tunable Lenses Based on Zipping Electroactive Polymer Actuators

“…[ 17,18 ] Yet, DEAs require high driving voltages in the kilovolts range and suffer from dielectric breakdowns, which irreversibly damage the lens (Table S1, Supporting Information). Actuators based on the displacement of dielectric liquids via zipping electroactive polymers (ZEAP) survive dielectric breakdown and have promising applications as artificial muscles for soft robotics [ 19,20 ] and wearable haptic displays, [ 21 ] but they require high driving voltages as well.…”

“…Omitting this connection can lead to directional inflation of the membrane, which is beneficial for other applications that involve touch, such as buttons or brail displays. [ 21 ] Heat‐sealing the electrodes in regular steps along the edge of the electrodes introduces specific starting points for zipping to improve the zipping homogeneity (we use this for all our lenses) and partially reduces the threshold voltage (Figure S3, Supporting Information). The dielectric fluid is a low viscosity paraffin oil with a refractive index n = 1.48 (close to PDMS); it is injected with a syringe through an access tube and sealed.…”

A Soft Touch: Wearable Tactile Display of Softness Made of Electroactive Elastomers

“…[ 28–30 ] This actuation strategy, which so far has been demonstrated for miniature (up to a few millimeters) tactile interfaces with displacements lower than 1 mm, might be challenged for higher displacements by the need for a larger lateral size, due to the zipping effect required for pressurization. [ 29,30 ]…”