Living beings use mechanical interaction with the environment to gather essential cues for implementing necessary movements and actions. This process is mediated by biomechanics, primarily of the sensory structures, meaning that, at first, mechanical stimuli are morphologically computed. In the present paper, we select and review cases of specialized sensory organs for mechanical sensing—from both the animal and plant kingdoms—that distribute their intelligence in both structure and materials. A focus is set on biomechanical aspects, such as morphology and material characteristics of the selected sensory organs, and on how their sensing function is affected by them in natural environments. In this route, examples of artificial sensors that implement these principles are provided, and/or ways in which they can be translated artificially are suggested. Following a biomimetic approach, our aim is to make a step towards creating a toolbox with general tailoring principles, based on mechanical aspects tuned repeatedly in nature, such as orientation, shape, distribution, materials, and micromechanics. These should be used for a future methodical design of novel soft sensing systems for soft robotics.

This paper presents a novel wireless inductive sensing technology to measure body deformation of soft pneumatic actuators (SPAs). The proposed technology exploits a magnetorheological elastomer (MRE) both as actuator's highly deformable skin and as target of the inductive sensor. When the MRE skin is deformed by internal driving and/or external load, the distance between the MRE and sensing coil changes, thereby the inductance. A flat SPA with an MRE skin is developed as a case study to validate and evaluate the proposed technology. A multiphysics finite element model is built to simulate the characteristics of the soft actuator and sensor as a single system. Experimental results highlight that this inductive sensing technology can measure the skin deformation with an effective resolution as high as 3 µm (RMS) at null deformation (50 µm at maximum deformation), without any hysteresis. Moreover, with pressure information, it is possible to retrieve both the deformation caused by internal driving and external load. A typical pneumatic bending actuator was developed to demonstrate its easy implementation in soft actuators. The presented technology does not require wires or mechanical connections between electronics and the deformable body, providing a promising sensing solution for SPAs and other soft systems.

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