Fig. 1a shows the overall structure of the fabricated DMFS, which consists of seven layers. The pressure sensing part is composed of SBS/PDA/CNT composite, SBS/PS@PANI composite, Ag interdigital electrodes and PI substrate film. The temperature sensing part is composed of PI substrate film, Ag interdigital electrodes, SBS/PDA/CNT composite and PDMS film. It is obviously observed in the SEM image in the lower-right corner (Fig. 1a) of the SBS/PDA/CNT composite that CNT is evenly attached to the surface of the SBS fiber film with the help of PDA to improve the SBS surface wettability and enhance the adhesion between the CNT and SBS fiber skeleton. The staggered network inside CNT [46] is supported by fiber skeleton SBS, which supports the large network formed by the whole CNT network structure, similar to the cobweb-like structure [47]. A cobweb-like CNT network among adjacent SBS fibers could greatly enrich the conductive pathway and improve the electrical conductivity of the composite film. A “sea urchin” structure PS@PANI (Fig. S1) is observed in the SBS/PS@PANI composite and randomly distributes throughout the layered SBS, as shown in the upper-right SEM image in Fig. 1a, and the SEM cross-section images of the “sea urchin” structure PS@PANI along the thickness is supplied in Fig. S2. When the DMFS is subjected to external pressure, the dispersed PS@PANI can contact with each other closely and the tunneling effect occurs, ensuring the high sensitivity for pressure sensing. Fig. 1b indicates the key steps for the fabrication of the DMFS. Firstly, fiber films often have good elasticity [48–50], a highly stretchable SBS fiber film (Fig. S3) is fabricated using a simple and inexpensive electrospinning method. Then, in order to prepare the SBS/PDA/CNT composite, the surface of SBS fiber film is wrapped with a thin layer of PDA by using a self-polymerization process (Fig. S4), and then CNT water dispersion is dripped onto SBS fiber film. The comparison of the water contact angle testing results of SBS fiber film before and after polymerization of DA is shown in Fig. 1c, and it is easily seen that the water contact angle is significantly reduced after PDA deposition. The introduction of PDA significantly improves the hydrophilicity of SBS fiber film, which is instrumental for enhancing the attachment of CNT to the SBS fiber surface. Besides, the energy dispersion spectrometer (EDS) mapping images of the SBS/PDA/CNT composite in Fig. S5 further proves that the CNT adhered to SBS uniformly. Furthermore, we examine the Raman spectra of the SBS/PDA/CNT composite (Fig. 1d). Radial Breathing Mode (RBM) is located at the low frequency band (100-500 cm−1) and Tangential Band (G-band) is located near 1580 cm−1. There is also a D-band (about 1350 cm−1) in the Raman spectra of CNT, which further confirms the existence of CNT in the SBS/PDA/CNT composite [51]. In addition, for preparing the SBS/PS@PANI sensing fiber layer, the “sea urchin” PS microspheres with PANI spines is obtained by in-situ polymerization of aniline. For better embedding of PS@PANI, the SBS fiber film is treated by using an oxygen plasma treatment method. And then, a subsequent vaccum filtration process promote the solid “sea urchin” structure PS@PANI to adhere to the SBS fiber film for obtaining SBS/PS@PANI composite. The EDS mapping results of C, O and N elements shown in Fig. S6 provide further evidence that PS@PANI is uniformly attached on SBS fibers.This work was supported by the National Natural Science Foundation of China under Grant (62174068), Rizhao City Key Research and Development Program under Grant (2021ZDYF010102).
