Wearable assistive tactile communication interface based on integrated touch sensors and actuators

This paper presents the design and fabrication of a wearable tactile communication interface with vibrotactile feedback for assistive communication. The interface is based on finger Braille, which is a simple and efficient tactile communication method used by deafblind people. It consists of a flexible piezoresistive sensor and a vibrotactile actuator integrated together and positioned at the index, middle and ring fingers of both hands to represent the six dots of Braille. The sensors were made using flexible piezoresistive material whereas the actuator utilizes electromagnetic principle by means of a flexible coil and a tiny NdFeB permanent magnet. Both were integrated to realize a Bluetooth-enabled tactile communication glove which enables deafblind people to communicate using Braille codes. The evaluation with 20 end-users (10 deafblind and 10 sighted and hearing person) of the tactile interface under standardized conditions demonstrated that users can feel and distinguish the vibration at frequencies ranging from 10Hz to 200Hz which is within the perceivable frequency range for the FA-II receptors. The results show that it took non-experts in Braille within 25s and 55s to send and receive words like “BEST” and “JOURNAL”, with an accuracy of ~75% and 68% respectively

Bioinspired Inchworm- and Earthworm-like Soft Robots with Intrinsic Strain Sensing

Stimulus-responsive soft structures, with biological organs like intrinsic sensing, are needed to enable controlled movements and hence bring the transformative advances in soft robotics. Herein, bioinspired inchworm- and earthworm-like soft structures with intrinsic strain sensing achieved by seamless embedding of a graphite-paste-based sensor material are presented. The developed strain sensor exhibits a record stretchability (900%) and sensitivity (of 103 up to ≈200 and of the order of 105 at around 700% linear strain). With tiny permanent magnets incorporated at the ends of these soft structures, the sensory-feedback-based controlled movements of magnetically driven inchworm- and earthworm-like soft robots are also demonstrated. The presented results potentially boost the prospects of self-sensing in soft robots and advance the field toward cognitive soft robotics

SensAct: the soft and squishy tactile sensor with integrated flexible actuator

Herein, a novel tactile sensing device (SensAct) with a soft touch/pressure sensor seamlessly integrated on a flexible actuator is presented. The squishy touch sensor is developed with custom‐made graphite paste on a tiny permanent magnet, encapsulated in Sil‐Poxy, and the actuator (15 μ‐thick coil) is fabricated on polyimide by Lithographie Galvanoformung Abformung (LIGA) micromolding method. The actuator can operate in two modes (expansion and contraction/squeeze) and two states (vibration and nonvibration). The sensor was tested with up to 12 N applied forces and exhibited ≈70% average relative resistance variation (ΔR/Ro), ≈0.346 kPa−1 sensitivity, and ≈49 ms response time with excellent repeatability (≈12.7% coefficient of variation) at 5 N. During simultaneous sensing and actuation, the modulation of coil current, due to ΔR/Ro (≈14% at 2 N force) in the sensor, allows the close loop control (ΔI/Io ≈385%) of expansion/contraction (≈69.8 μm expansion in nonvibration state and ≈111.5 μm peak‐to‐peak in the vibration state). Finally, the soft sensor is embedded in the 3D‐printed fingertip of a robotic hand to demonstrate its use for pressure mapping along with remote vibrotactile stimulation using SensAct device. The self‐controllable actuation of SensAct could provide eSkin the ability to tune stiffness and the vibration states could be utilized for controlled haptic feedback

Graphite-based bioinspired piezoresistive soft strain sensors with performance optimized for low strain values

This paper presents the custom-made graphite-based piezoresistive strain sensor with gecko foot-inspired macroscopic features realized using a Velcro tape on Ecoflex substrate. The Velcro-based design provides an inexpensive and easy approach for the development of soft sensors with appreciable improvement in the performance even at low strain values. The sensor demonstrated excellent response (sensitivity of ∼16 500%, gauge factor of ∼3800) for 24% linear strain. The fabricated device showed a high gauge factor (>100) even for very low strain values. The sensor has been extensively characterized with a view to potentially use in soft robotics applications where high performance is needed at lower strain values. It is observed that the piezoresistive behavior of strain sensors is governed by several factors such as the supporting elastic medium, architecture of the strain sensor, material properties, strain rate and deformation sequence, and direction

Bioinspired inchworm- and earthworm-like soft robots with intrinsic strain sensing

Stimulus-responsive soft structures, with biological organs like intrinsic sensing, are needed to enable controlled movements and hence bring the transformative advances in soft robotics. Herein, bioinspired inchworm- and earthworm-like soft structures with intrinsic strain sensing achieved by seamless embedding of a graphite-paste-based sensor material are presented. The developed strain sensor exhibits a record stretchability (900%) and sensitivity (of 103 up to ≈200 and of the order of 105 at around 700% linear strain). With tiny permanent magnets incorporated at the ends of these soft structures, the sensory-feedback-based controlled movements of magnetically driven inchworm- and earthworm-like soft robots are also demonstrated. The presented results potentially boost the prospects of self-sensing in soft robots and advance the field toward cognitive soft robotics

Magnetic properties of FeCo alloy nanoparticles synthesized through instant chemical reduction

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