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Moreover, TPU conductive polymer composed of conductive ingredients and insulating TPU matrix can be used in applications of smart sensors, electromagnetic shielding, and oil-water separation. [11][12][13][14][15][16] Through introducing a 3D porous structure to TPU conductive polymer while utilizing the advantageous abilities of light weight, large specific surface area, and high porosity of the porous structure, [17][18][19][20][21] the TPU conductive polymer foam can achieve excellent flexibility and piezoresistive performance by combining its mechanical and electrical properties, exhibiting great potential in applications of flexible pressure sensors. [22][23][24][25][26][27] In recent years, TPU conductive polymer foam has been extensively studied in field of flexible pressure sensors. This material can further be subdivided into carbon black (CB)/TPU conductive foam, carbon nanotubes (CNT)/TPU conductive foam, and graphene (G)/TPU conductive foam in terms of the conductive filler types. The 0D CB featuring with outstanding advantages in good conductivity, small size, cost-efficient, and easy availability, which can be prepared the conductive TPU foam. [28][29][30][31] Guan et al. prepared a CB/TPU foam which exhibits its performance in measuring range (20 Pa to 1.2 MPa) and sensitivity (1.12 kPa −1 ). [22] The CB/TPU foam fabricated by Zhai et al. displays a response/relaxation time (150/150 ms), workable detection range (584.4 kPa) and durability (more than 10 000 cycles at 15 kPa). [32] The 1D CNT featuring with exceptional mechanical properties, high electrical conductivity, large vertical and horizontal ratio, has been acknowledged as an ideal filler for conductive polymer composite materials. [33][34][35] Liu et al. prepared a compressible (90%) CNT/TPU foam which displays piezoresistive recoverability (50 cycles). [23] In order to improve electromechanical properties of the TPU conductive foam, two methods involving conductive foam pore design and conductive composite matrix control can be adopted. Huang et al. prepared a CNT/TPU conductive foam with aligned porous structure, realizing a linear detection range of 77% (0.92 MPa) and 2000 (6 kPa) cycle stability. [24] Wei et al. prepared a herringbone structured CNT/EP/TPU foam by using epoxy resin (EP) as Flexible pressure sensors based on thermoplastic polyurethane (TPU) conductive polymer foam can be applied to health monitoring, motion detection, and electronic skin. For satisfying the demand of long-term use in highpressure range, the TPU conductive polymer foam requires improvements in detection range, stability, and repeatability. In this paper, a flexible conductive reduced graphene oxide (rGO)/thermoplastic polyurethane (TPU) porous foam with ultra-wide pressure detection range and high-stability is proposed. First, an elastic and flexible TPU polymer foam matrix is fabricated via freezedrying. Then, the rGO/TPU foam is prepared by dip-coating it into graphene oxide (GO) solution followed by chemical reduction. The electromechanical properties ...

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Flexible pressure sensors have attracted a considerable amount of attention in various fields including robotics and healthcare applications, among others. However, it remains significantly challenging to design and fabricate a flexible capacitive pressure sensor with a quite broad linearity detection range due to the nonlinear stress–strain relation of the hyperelastic polymer-based dielectric material. Along these lines, in this work, a novel flexible capacitive pressure sensor with microstructured composite dielectric layer (MCDL) is demonstrated. The MCDL was prepared by enforcing a solvent-free planetary mixing and replica molding method, while the performances of the flexible capacitive pressure sensor were characterized by performing various experimental tests. More specifically, the proposed capacitive pressure sensor with 4.0 wt % cone-type MCDL could perceive external pressure loads with a broad detection range of 0–1.3 MPa, which yielded a high sensitivity value of 3.97 × 10−3 kPa−1 in a relative wide linear range of 0–600 kPa. Moreover, the developed pressure sensor exhibited excellent repeatability during the application of 1000 consecutive cycles and a fast response time of 150 ms. Finally, the developed sensor was utilized for wearable monitoring and spatial pressure distribution sensing applications, which indicates the great perspectives of our approach for potential use in the robotics and healthcare fields.

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Electronic skin with high sensitivity, rapid response, and long-term stability has great value in robotics, biomedicine, and in other fields. However, electronic skin still has challenges in terms of sensitivity and response time. In order to solve this problem, flexible electronic skin with high sensitivity and the fast response was proposed, based on piezoresistive graphene films. The electronic skin was a pressure sensor array, composed of a 4 × 4 tactile sensing unit. Each sensing unit contained three layers: The underlying substrate (polyimide substrate), the middle layer (graphene/polyethylene terephthalate film), and the upper substrate bump (polydimethylsiloxane). The results of the measurement and analysis experiments, designed in this paper, indicated that the flexible electronic skin achieved a positive resistance characteristic in the range of 0 kPa–600 kPa, a sensitivity of 10.80 Ω /kPa in the range of 0 kPa–4 kPa, a loading response time of 10 ms, and a spatial resolution of 5 mm. In addition, the electronic skin realized shape detection on a regular-shaped object, based on the change in the resistance value of each unit. The high sensitivity flexible electronic skin designed in this paper has important application prospects in medical diagnosis, artificial intelligence, and other fields.