High-Performance Flexible Capacitive Proximity and Pressure Sensors with Spiral Electrodes for Continuous Human–Machine Interaction

Abstract

Flexible perception sensors play important roles in the artificial intelligence era. An integrated proximity and tactile pressure sensor, with the capability to continuously perceive the approach of an object until a pressure variation is sensed through contact and manipulation, is in demand for the improvement of proximity-sensing distance, flexibility, and integration. Herein, capacitive proximity and pressure dualmode sensors based on a novel complementary Archimedean spiral electrode design and dielectric calcium cross-linked alginate film are reported. The results of theoretical analysis and finite element simulation show that the electrode pattern design with a higher specific fringe length (i.e., fringe length divided by electrode cover area) significantly enhances the fringe field. As the dielectric layer, the flexible and transparent calcium cross-linked alginate film with crater-shaped morphology is prepared by a novel interfacial reaction method with ultrasonic spraying that improves the sensitivity and linearity of the tactile perception response. Sensors with optimized electrodes and dielectric layers exhibit unprecedented performance in terms of high sensitivity, long detection distance (∼55 mm), fast responding time (<10 ms), and highly linear response (R 2 = 0.995). Furthermore, the applications of the integrated perception sensors for noncontact tapping and swiping gesture recognition and continuous human−machine interaction for controlling image scaling are demonstrated.

Ionic skin: from imitating natural skin to beyond

“…At present, the methods of noncontact perception mainly include humidity sensing, 65,66 triboelectric sensing, [67][68][69] infrared radiation sensing, 70 magnetic sensing 71 and capacitive sensing. 72,73 The sensing modes suitable for ionic skin are mainly based on triboelectric sensors, humidity and capacitive sensors.…”

High-Performance Dual-Responsive Sensing Skin Enabled by Bioinspired Transduction of Coplanar Square-Loop Electrodes

“…Capacitive proximity and tactile sensing capabilities are significantly affected by the electrode pattern and dielectric structures. 34 To investigate the impact of various electrode configurations systematically, we simulated the electric field distribution for two types of parallel electrodes: (i) parallel plate and (ii) loop and square, as well as two types of coplanar electrodes: (iii) square ring and (iv) square-loop. The simulation setup is depicted in Figure S3 with detailed descriptions provided in the Experimental Section.…”

“…Despite the above advantages, some common challenges of capacitive DASs, such as a limited proximal sensing distance and low touch sensitivity, remain to be addressed. Specifically, since the capacitive DAS detects incoming objects through the disturbance in the fringe field, researchers have attempted to enhance the intensity of the fringe field by designing the parallel electrodes into interdigitated, disc-like, and spiral shapes. ,− Although designed electrode patterns have improved the relative performance of proximity perception to some extent, this enhancement comes at the cost of a compromised pressure-sensing ability. The maximum pressure sensitivities of these studies have dropped to about 5 MPa –1 while achieving excellent proximity-sensing capabilities .…”

Fiber-Based Noncontact Sensor with Stretchability for Underwater Wearable Sensing and VR Applications

“…Therefore, the noncontact sensing function and underwater detection capability will be the priorities of the next generation of HMI systems, especially in the COVID-19 pandemic and postepidemic period. ,,,, Conventional noncontact methods including radar and infrared sensors can be used to detect the approaching of hands, ,, but the complex signal processing circuit and relatively high cost limit their widespread adoption. One of the potential candidates to address these challenges is the wearable capacitive sensor built upon hydrophobic helical fibers, which primarily relies on the inductive coupling effect of the human body to induce capacitance changes. ,− …”