Cascade Amplification Effect for Mechanical Stimuli Sensors by Designing the Current Path Through Carbon Fiber Beams

Inspired by the tandem structure can be used as an effective approach to improving the performance of optoelectronic devices such as solar cells and organic light emitting diodes, a series of mechanical sensors with high performance were fabricated on a flexible sheet (thickness, less than
$300~\mu \text{m}$
) based on tandem structures. In our designed tandem structure models, the single sensing unit consisting of one single carbon fiber beam presents nonlinear behavior when responding to force stimuli. Thus, the initial resistance and resistance change value of the tandem mechanical sensors could be enhanced by increasing the number of sensing units to lengthen the current path through carbon fiber beams and enable the sensor to respond to subtle force after preloading a large force. Moreover, the tandem mechanical sensors can measure force quantitatively due to the corresponding relationship between the resistance change rate and the loading force. These combined advantages of the tandem mechanical sensors were also demonstrated by the successful application in weighed, softness discrimination and texture discrimination, implying that these mechanical sensors could be used as mechanoreceptors like a finger touching in monitoring daily life sensations.