Fig. 1. (Color online) Schematic of nanofibers/nanowires-based flexible and stretchable sensors.

Fig. 2. (Color online) Graphical summaries of advantages of possible flexible and stretchable sensors application of 1D nanofibers/nanowires materials.

Fig. 3. (Color online) (a) Illustration of the preparation and structure of the Au nanowires-based flexible pressure sensor. (b) Optical image of the Au nanowires-based flexible pressure sensor. Inset show the SEM image of Au nanowires (scale bar, 100 mm). (c) Optical image of device attached on the wrist. (d) pulse change records of device attached on the wrist. (e) Schematic illustration of the setup for acoustic vibration sensing. (f) The current responses to the acoustic vibrations from a piece of music. Reproduced from Ref. [70] with permission, Copyright 2014, Macmillan Publishers Limited. (g) Illustration of the preparation process of vertically arranged gold nanowires on microstructured PDMS films. (h) Schematic showing the sensor structure. (i) Response time and recovery time of vertically arranged gold nanowires-based flexible pressure sensor under both loading and unloading conditions. Reproduced from Ref. [71] with permission, Copyright 2019, American Chemical Society.

Fig. 4. (Color online) (a) Illustration of fabrication process of rGO/PVDF nanofibers-based flexible pressure sensor. (b) SEM image of rGO/PVDF nanofibers. (c) Illustration of a flexible pressure sensor structure. (d) Sensitivity of rGO/PVDF nanofibers-based flexible pressure sensor under different force conditions. (e) dynamic response curves of rGO/PVDF nanofibers-based flexible pressure sensor for different objects. (f, g) Response curves of rGO/PVDF nanofibers-based flexible pressure sensor attached on the wrist under different condition. Reproduced from Ref. [72] with permission, Copyright 2016, Elsevier B.V. (h, i) Structure and fabrication process of the PVR system. SEM image of the as-obtain (j) ZnO nanowire and (k) WO₃ film array. Enlarged SEM images of (j1, j2) the ZnO nanowire before and after spin-coating the photoresist layer and (k1, k2) The WO₃ film deposited on the ITO electrode. Reproduced from Ref. [74] with permission, Copyright 2017, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. (l) Pressure response of the PTNWs/G-based sensors. (m) dynamic pressure-sensing curves of the PTNWs/G-based sensors. Reproduced from Ref. [ 75] with permission, Copyright 2017, American Chemical Society.

Fig. 5. (Color online) (a) Schematic structure and (b) high-magnification SEM image of the P(VDF-TrFE)-based conductive fiber. (c) Pulse and (d) spoke response curves of the P(VDF-TrFE)-based fibrous sensor. (e) A data glove fixed with ten-fiber strain sensors. Reproduced from Ref. [85] with permission, Copyright 2016, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. (f) Illustration of preparation process and (g) optical image of Ag nanowires/PDMS-based sandwich-structured strain sensors. (h) Optical image of the Ag nanowires/PDMS-based strain sensor under bending and twisting. (i) optical images on top and cross-section of Ag nanowires/PDMS-based strain sensor. (j) Finger motion detection and (k) smart glove system by Ag nanowires/PDMS-based sandwich-structured strain sensors. Reproduced from Ref. [ 60] with permission, Copyright 2014, American Chemical Society.

Fig. 6. (Color online) (a) Illustration of fabrication process of SWCNT-based strain sensor. (b) Optical image of the SWCNT-based strain sensor under strain. (c) SEM image of SWCNT. (d) Stretchable wearable sensors on the human body. (e) Finger motion detection of stretchable wearable sensors. Reproduced from Ref. [87] with permission, Copyright 2011, Macmillan Publishers Limited. (f) Illustration of fabrication process of CNT-based strain sensor. (g) Optical images of the CNT-based strain sensor. (h) Top-view and (i) cross-section view SEM image of CNT materials. (j) Brushing test and (k) joystick movements of CNT-based strain sensors. Reproduced from Ref. [88] with permission, Copyright 2019, The Royal Society of Chemistry.

Table 1. Summary of various 1D nanostructure materials based flexible and stretchable sensors.