Abstract
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.
Highlights
A novel tactile sensing device (SensAct) with a soft touch/pressure sensor structures,[6] morphology,[7] and transduction methods.[8]
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 integrated touch sensing, actuation, and computation into soft 3D structures[10] is a salient feature of human skin[11] which helps to tune some of the functionalities.[1e] electronic skin (eSkin) with such features could enable a new generation of truly smart and complex systems such expansion/contraction (%69.8 μm expansion in nonvibration state and %111.5 μm as robots having human like dexterity, peak-to-peak in the vibration state)
The selfcontrollable actuation of SensAct could provide eSkin the ability to tune stiffness and the vibration states could be utilized for controlled haptic feedback
Summary
During simultaneous operation of sensor and actuator in SensAct (Figure 2c), an external pressure on the sensing layer results in change in resistance (ΔR). This resistance shift causes a change in the current (ΔI) produced by the actuating control module which is utilized to drive the actuating coil. Actuation occurs and the sensing layer moves away from the coil (expansion mode) or closer to the coil (contraction mode) depending on the direction of current This means that the current through the coil can be modulated by the amount of external force on the sensing layer, which in turn controls the position of the sensing layer. Further details of the control mechanism including the actuation control module are shown in Figure S3, Supporting Information
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