A Multimodal Hydrogel Soft-Robotic Sensor for Multi-Functional Perception

Abstract

Soft robots, with their unique and outstanding capabilities of environmental conformation, natural sealing against elements, as well as being insensitive to magnetic/electrical effects, are ideal candidates for extreme environment applications. However, sensing for soft robots in such harsh conditions would still be challenging, especially under large temperature change and complex, large deformations. Existing soft sensing approaches using liquid-metal medium compromise between large deformation and environmental robustness, limiting their real-world applicability. In this work, we propose a multimodal solid-state soft sensor using hydrogel and silicone. By exploiting the conductance and transparency of hydrogel, we could deploy both optical and resistive sensing in one sensing component. This novel combination enables us to benefit from the in-situ measurement discrepancies between the optical and electrical signal, to extract multifunctional measurements. Following this approach, prototype solid-state soft sensors were designed and fabricated, a dedicated neural network was built to extract the sensory information. Stretching and twisting were measured using the same sensor even at large deformations. In addition, exploiting the distinctive responses against temperature change, we could estimate environmental temperatures simultaneously. Results are promising for the proposed solid-state multimodal approach of soft sensors for multifunctional perception under extreme conditions.

Hydrogels in Soft Robotics: Past, Present, and Future

“…It is the case of the proprioceptive sensor integrated in our pneumatic soft actuator, which provides the curvature of the actuator, allowing its automatic control. Some works combine conductivity with other stimuli-responses to create multipurpose sensors, like the sensor proposed by Cheng et al Thanks to the conductivity and optical transmission of the hydrogel used, the sensor can provide information about different mechanical strains (stretching and twisting) and ambient temperature by using neural networks to analyze all the sensed data.…”

Soft Optical Waveguides for Biomedical Applications, Wearable Devices, and Soft Robotics: A Review

“…[79] As information technology continues to advance, there is a desire for sensing devices to be multifunctional in order to obtain a range of information about bending, pressing and stretching, and to collect information into smart devices, like gamer gloves to analyze and extract them. [80][81][82][83][84][85] Heiden et al proposed a 3Dprinting process based on fused deposition modeling to fabricate stretchable waveguides capable of both proprioceptive and extrinsic sensations. [68] The proposed soft waveguide is a bare waveguide without cladding.…”

Shape perception of soft hand based on dual-signal comparison contact detection

“…Some flexible sensors can directly measure the bending angle or bending curvature. These sensors often use the change rule of physical quantities such as resistance (Butt et al , 2018; Nassour et al , 2018), capacitance (Rocha et al , 2018), luminous flux (Chen et al , 2019; Cheng et al , 2021; Wurdemann et al , 2015; Yang et al , 2020; Zhao et al , 2016) and magnetic field (Ozel et al , 2016) during bending, to realize their work. Among them, resistive bending sensors are the most common, including commercial bending sensors (Elgeneidy et al , 2018; Homberg et al , 2015; Soter et al , 2018; Vidisha, 2017; Wang and Hirai, 2016), coiled conductive polymer fibers (Tang et al , 2018), hydrogel (Wang et al , 2021), liquid metal (Adam Bilodeau et al , 2015).…”