Wireless and Flexible Tactile Sensing Array Based on an Adjustable Resonator with Machine‐Learning Perception

Abstract

between systems and objects. [1][2][3][4][5] Sensor arrays have been demonstrated to realize high-sensitivity haptic position sensing, [6] objects recognition, [7] force direction detection, [8,9] modulus measurement, [10] texture recognition, [11] and other comprehensive multisensory functions. [3,12,13] However, when numerous sensors are implemented in the human body or installed on machines with complex actions, power supplies and signal lines become intractable obstacles. [14,15] To solve this issue, passive and wireless radiofrequency (RF) resonant sensors, have received considerable attention as promising candidates for hard-to-wire scenarios. [16][17][18][19][20] These sensors can be flexibly mounted on the moving part or inside the sealing equipment because they use RF electromagnetic waves to exchange energy and signals directly, eliminating the need of wiring and batteries. Examples include the wind-pressure probes on the propellers, [18] noninvasive detection inside the pipelines, [21,22] and the longendurance monitoring of air chambers and tire pressure. [23,24] Moreover, the combination of RF technology and soft materials can build a bridge from the human body to machines, such applications involve nanowire contact lenses for intraocular pressure monitoring, [17] arterial-pulse sensors for bloodflow monitoring, [16] and biodegradable implanted devices for intracranial pressure measurement. [25,26] Although wireless RF sensing technology has demonstrated considerable application potential, the array construction of RF tactile sensors still faces several challenges. In typical sensor array based on split-ring resonator (SRR) arrays [27][28][29] or compact inductor-capacitor (LC) arrays, [30][31][32] sensor units are required to operate at various frequencies. According to the existing methods, different inductance geometries need to be constructed for this purpose, which requires a complex micromachining process owing to the limited device area. Simultaneously, different inductances result in an irregular and incalculable mutual inductance between neighbors, which causes clutter interference while reading. Moreover, the shift of the resonant peak in the scatter spectrum is typically read as a response to the applied pressure. A common drawback is that the frequency sensor array needs to provide an independent operating frequency range for each sensitive Intelligent soft robotics and wearable electronics require flexible, wireless radio frequency (RF) pressure sensors for human-like tactile perception of their moving parts. Existing devices face two challenges for array extension: the construction of sensitive units over a limited area and the handling of resonant peaks overlapping within the channel width. Herein, a simply adjustable RF-resonator-based tactile array (RFTA) is reported, in which the initial frequency of each resonator unit is regulated by doping polydimethylsiloxane (PDMS) dielectric layers with various concentrations of multiwalled carbon nanotubes (MWCNTs). An array is constructed usi...

Integration of Flexible Touch Panels and Machine Learning: Applications and Techniques

“…In a report by Xu et al, [118] a flexible RF-resonator-based tactile array (RFTA), as shown in Figure 8f, was introduced. This array can accurately identify tactile positions through ML and differentiate between various objects during the grasping process by soft robotic hands.…”

Single-Line Multi-Channel Flexible Stress Sensor Arrays

“…SLMC measurement can simultaneously measure multiple sensor signals using one or two signal wires. Depending on the mechanism, SLMC measurement can be classified into various types, including RLC resonant sensing [ 15 , 28 , 29 , 32 ], transmission line sensing [ 16 ], ionic conductor sensing [ 33 , 36 ], triboelectric sensing [ 42 , 43 ], piezoresistive sensing [ 41 ], and distributed fiber optic sensing [ 34 ].…”

“…To address this challenge, the single-line multi-channel (SLMC) signal measurement has been developed, enabling simultaneous detection of multiple sensor signals through one or two signal wires [ 15 , 16 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. By utilizing SLMC technology, the flexible stress sensor array can measure the magnitude and location of the stress by one or two signal lines.…”

Recent Advances in Tactile Sensory Systems: Mechanisms, Fabrication, and Applications

“…This greatly increases both the energy consumption and the complexity of the system. Typically, the tactile sensors are spatially separated from the neuromorphic devices, limiting the development and application of highly integrated intelligent sensing networks [ 27 , 30 , 31 , 32 , 33 ]. Therefore, research into a biomimetic neuromorphic tactile sensing system coupled with intrinsic sensing mechanisms may be an effective solution.…”