Abstract
Measurement of the internal stress and strain distributions within soft materials is necessary in the field of skin contact safety. However, conventional interactive force sensors cannot efficiently obtain or estimate these distributions. Herein, a shear strain sensor system consisting of distributed built-in piezoelectric polyvinylidene fluoride (PVDF) polymer films was developed to measure the internal shear strain field of a soft material. A shear strain sensing model was mathematically established, based on the piezoelectricity and mechanical behavior of a bending cantilever beam, to explain the sensing principle. An experiment in three-dimensional measurement of the shear strain distribution within an artificial skin was designed and conducted to assess the sensitivity of the sensing model. This sensor system could visualize the shear strain field and was sensitive to different contact conditions. The measurement results agreed well with the results of numerical simulation of the substrate, based on contact mechanics. The proposed sensor system was confirmed to provide a new sensing method for the field of shape analysis. The sensor system can be applied to develop sufficiently sensitive electronic skin and can significantly contribute to skin damage analysis and skin contact safety assessment.
Highlights
Soft materials play important roles in everyday life and in a wide range of technological applications.The mechanical properties of soft materials are characterized in terms of elasticity, plasticity, and viscosity [1].Some soft materials exhibit anisotropy or multilayer structures
In regards to the position of the neutral layer, which appears in the equations above, the calculation of the distance from the center of the polyvinylidene fluoride (PVDF) layer to the neutral axis hc is discussed based on the mechanical structure of the sensor element
The measurement results indicated that the internal shear strain field within an artificial skin could be visualized by the proposed sensor system
Summary
Soft materials play important roles in everyday life and in a wide range of technological applications. This safety standard clearly states that degrees of skin–robot friction and shear stress should be reduced to avoid injury, quantitative requirements for achieving this goal are not stated Pressure ulcers are another type of injury to the skin and underlying tissue that result from prolonged pressure and frictional forces [11]. Recent research in electronic artificial skin has assembled excellent designs with high sensitivity, stretchability, and reliability [20,21] These measurement targets were still limited in terms of the interactive force, by embedding the sensing element within a substrate, built-in structures as these provide a good starting point for designing a sensor system for internal stress or strain distribution measurements. We monitored the internal mechanical conditions of a soft material using a novel sensor system with a distributed built-in sensing element composed of PVDF polymer film. The effect of the shape of the contactor on the strain distribution was investigated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
