fig3

Figure 3. Fabrication process and signal measurements of piezoelectric and capacitance-based mechanical strain sensors. (A) Schematic illustrations of mechanical sensor operating mechanisms: piezo-resistivity, capacitance, and piezoelectricity. Reprinted with permission from ref^[34]. Copyright 2020, Elsevier; (B) Fabrication method of PEDOT on a PS fiber for realizing textile sensors; (C) Optical images of linear- and zigzag-type textile strain sensors embedded in fabrics. Reproduced with permission from ref^[36]. Copyright 2017, American Chemical Society; (D) 3D images of the CSF strain sensor fabrication; (E) Photograph of the wearable sensors weaved into a stocking. The inset is a magnified image; (F) Resistance changes graph of the wearable sensor at the movements of flexing/extending, marching, jogging, jumping, and squatting-jumping. Reproduced with permission from ref^[37]. Copyright 2016, John Wiley and Sons; (G) Schematic of experimental setup for fabricating the flexible strain gauge through the spraying process. Reproduced with permission from ref^[39]. Copyright 2022, American Chemical Society; (H) Photograph of e-3DP for a planar array of soft strain sensors. Reproduced with permission from ref^[40]. Copyright 2014, John Wiley and Sons; (I) Microscopic images of the PDMS/hexane nanomesh with various weight ratios 1/40 (left) and 1/80 (right); (J) Photograph of nanomesh based-sensor (left side) and control device array (right side) attached on the face during speech of “a” (K) Strain distribution images during speech of “a” with nanomesh-based sensor (left) and control one (right). Reproduced with permission from ref^[41]. Copyright 2020, AAAS. PEDOT: Poly(3,4-ethylenedioxythiophene); PS: polyester; 3D: three-dimensional; CSF: carbonized silk fabric; e-3DP: embedded 3D printing; PDMS: polydimethylsiloxane.