Ultra-stable and tough bioinspired crack-based tactile sensor for small legged robots

Abstract

For legged robots, collecting tactile information is essential for stable posture and efficient gait. However, mounting sensors on small robots weighing less than 1 kg remain challenges in terms of the sensor’s durability, flexibility, sensitivity, and size. Crack-based sensors featuring ultra-sensitivity, small-size, and flexibility could be a promising candidate, but performance degradation due to crack growing by repeated use is a stumbling block. This paper presents an ultra-stable and tough bio-inspired crack-based sensor by controlling the crack depth using silver nanowire (Ag NW) mesh as a crack stop layer. The Ag NW mesh inspired by skin collagen structure effectively mitigated crack propagation. The sensor was very thin, lightweight, sensitive, and ultra-durable that maintains its sensitivity during 200,000 cycles of 0.5% strain. We demonstrate sensor’s feasibility by implementing the tactile sensation to bio-inspired robots, and propose statistical and deep learning-based analysis methods which successfully distinguished terrain type.

Strain versus Tunable Terahertz Nanogap Width: A Simple Formula and a Trench below

“…Indeed, the measured gap width precisely follows the simplistic phenomenological Equation (1) ( Figure 2 b). Strain singularities are formed where the gaps are located [ 66 , 67 , 68 ], which would exert enormous force on the PET below the Au gap at which nonlinear tearing will occur, generating trenches effectively canceling the initial singularity [ 69 , 70 ]. This trench will smooth out the opening and closing of the nanogap structure, ensuring repeatability of the performances [ 41 ], forming free-standing gaps on top of the PET trench to ensure the phenomenological validity of Equation (1).…”

The role of bio-inspired micro-/nano-structures in flexible tactile sensors

“…10(c). 121 The authors integrated the strain sensor into the robot's legs to understand the robot's gait, step frequency and terrain type by analyzing the peak-to-peak interval and peak height of the signals generated when the robot's feet touched the ground. Data were collected for the robot running on four types of terrain: flat, uphill, downhill, and gravel.…”

Advances in advanced solution‐synthesis‐based structural materials for tactile sensors and their intelligent applications

“…Conductor NWs are typically randomly interspersed on an elastic polymer substrate through methods such as spin‐coating, spray‐coating, or dip‐coating, to construct an active layer of tactile sensors 95–98 . However, the non‐uniform distribution of conductor NWs and the physical adhesion between the NWs and the polymer substrate may lead to stability issues during long‐term tactile sensing 99 .…”