Cost-Efficient Flexible Supercapacitive Tactile Sensor With Superior Sensitivity and High Spatial Resolution for Human-Robot Interaction

Abstract

Tactile sensing is crucial for the safety, accuracy and robustness of the human-robot interactions in the fields of wearable equipment, service robots and healthcare robots. Although many efforts have been made, it still requires much work to develop functional and reliable flexible tactile sensors with superior sensitivity, wide measurement range, high spatial resolution and low cost based on simple structures and easy fabrication. Here, this paper introduces a flexible supercapacitive tactile sensor with outstanding and balanced performance. The tactile sensor contains two layers of flexible electrodes and a layer of ionic-gel coated microfiber matrix to form a supercapacitive sensing structure. The flexible electrodes and the ionic microfiber matrix are processed with scalable techniques such as screen printing and gel-coating, which guarantee the ultra-flexibility and low fabrication cost. The experimental data suggests strong linearity in the pressure-capacitance relationship and high sensitivity (135.9 nF•kPa −1 •cm 2 or 27.11 kPa −1). Wide pressure measurement range (from 0 kPa to 1200 kPa) is also achieved by balancing structure parameters. Dynamic responses of the tactile sensors could accurately reflect the applied pressure cycles from human-finger tapping and machine pressing. The tactile sensor can map the pressure distribution with a high spatial resolution (>2 points•mm −2) when connected with the specially designed electric circuitry. The spatial resolution from sub-mm to large area makes it promising for various sensing applications in human-robot interactions, from finger touch to body contact. The developed tactile sensor in this study owns superior applicability and universality which makes it a trustworthy candidate to benefit various applications in robotics, flexible electronics and bioengineered equipment.

Flexible Pseudocapacitive Iontronic Tactile Sensor Based on Microsphere‐Decorated Electrode and Microporous Polymer Electrolyte for Ultrasensitive Pressure Detection

“…Particularly, certain kind of polymers (e.g., polyvinyl alcohol (PVA), polyurethane (PU), and Polydimethylsiloxane (PDMS)) can be added into a liquid electrolyte to form a polymer electrolyte, which endows the whole sensor device superior elasticity, flexibility, and stretchability. [53][54][55] In the past, great efforts have been dedicated in the design and fabrication of various types of ionic electrolyte (e.g., acid/alkali/ salt/ionic liquid and hydrogel/ionic gel) by using the highly conductive carbon (e.g., carbon nanotubes [2,56] ), MXene, [1,57] and silver (e.g., silver nanowires, [58] silver nanoparticle [59] )based electrodes, where only the supercapacitive EDLC takes effect. While in the electrochemical capacitor (commonly known as supercapacitor) field, transition metal oxides (e.g., MnO 2 , Co 3 O 4 ) and conducting polymers (also known as π-conjugated polymers, e.g., polyaniline (PANi), polypyrrole (PPy), polythiophene (PTh) and its derivants) are widely used as the active electrode material to form the pseudocapacitor, which works on the fast redox reactions (also known as Faradaic reactions) at the surface and several-nanometer depth beneath the surface of the electrode.…”

“…It has been verified that pseudocapacitors possess much higher specific capacitance than EDLCs. [1,54,55] Thus it would be of great appealing to apply the pseudocapacitive working mechanism to the development of iontronic tactile sensors for the purpose of achieving further enhanced sensing performance, but rarely has it be done so far.…”

RobotSweater: Scalable, Generalizable, and Customizable Machine-Knitted Tactile Skins for Robots

“…Rigid tactile sensors can cover large areas using modular approaches [2]. Flexible tactile sensors can further fit on robots with complex geometries [3], [13].…”

“…Flexible and deformable robot skins [3], [4] have desired mechanical properties to adapt to various robots and cover curved surfaces. One prevalent flexible and deformable material is textile, and the textile manufacturing industry has automated fabrication procedures that generalize to different shapes and produce fabrics at scale.…”

Development of a Soft Tactile Sensor Array for Contact Localization Estimations

“…Soft tactile sensors are mainly designed using biological inspiration from human skin, which has distributed mechanical receptors that can sense force, stiffness, temperature, texture, and vibration [8], [9], [10]. These sensors are based on optical [11], [12], [13], [14], resistive [15], [16], [17], capacitive [18], [19], [20], [21], magnetic [22], [23], [24], [25], inductive [26], [27], [28] and piezoelectric [29], [30], [31], [32], [33] principles. Besides these soft tactile sensors, vision-based sensors are also used for tactile perception in robotics [34], [35], [36], [37], [38], [39].…”