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Intelligent human-machine interfaces (HMIs) integrated wearable electronics are essential to promote the Internet of Things (IoT). Herein, a curcumin-assisted electroless deposition technology is developed for the first time to achieve stretchable strain sensing yarns (SSSYs) with high conductivity (0.2 Ω cm −1) and ultralight weight (1.5 mg cm −1). The isotropically deposited structural yarns can bear high uniaxial elongation (>>1100%) and still retain low resistivity after 5000 continuous stretching-releasing cycles under 50% strain. Apart from the high flexibility enabled by helical loaded structure, a precise strain sensing function can be facilitated under external forces with metal-coated conductive layers. Based on the mechanics analysis, the strain sensing responses are scaled with the dependences on structural variables and show good agreements with the experimental results. The application of interfacial enhanced yarns as wearable logic HMIs to remotely control the robotic hand and manipulate the color switching of light on the basis of gesture recognition is demonstrated. It is hoped that the SSSYs strategy can shed an extra light in future HMIs development and incoming IoT and artificial intelligence technologies.

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In this paper, the snap-through buckling of an initially curved microbeam subject to an electrostatic force, accounting for fringing field effect, is investigated. The general governing equations of the curved microbeam are developed using Euler-Bernoulli beam theory and used to develop a new criterion for the snap-through buckling of that beam. The size effect of the microbeam is accounted for using the modified couple stress theory, and intermolecular effects, such as van der Waals and Casimir forces, are also included in our snap-through formulations. The snap-through governing equations are solved using Galerkin decomposition of the deflection. The results of our work enable us to carefully characterize the snap-through behaviour of the initially curved microbeam. They further reveal the significant effect of the beam size, and to a much lesser extent, the effect of fringing field and intermolecular forces, upon the snap-through criterion for the curved beam.

a b s t r a c tIn this paper, we extend the earlier studies to investigate the effects of various parameters which govern the symmetric snap-through buckling of an initially curved microbeam subject to an electrostatic force. The governing formulations are developed using Euler-Bernoulli beam theory. The mid-plane stretching experienced during the snap-through buckling is considered using von Karman nonlinear strain, and the nonzero strain component is determined and solved using Galerkin decomposition approach. The studied parameters include: beam fixation type (double-clamped and simply-supported), arch shape, residual axial force, and uniform temperature variation. The results of our work reveal the significant effects of the type of the beam fixation, the residual force, and the temperature variation on the criterion for the symmetric snap-through buckling of microbeams, while the effect of the arch shape is somewhat insignificant.