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Flexible pressure sensors with high sensitivity and wide pressure response range are attracting considerable research interest for their potential applications as e-skins. Nowadays, it seems a dilemma to realize high-performance, multifunctional pressure sensors with a cost-effective, scalable strategy, which can simplify wearable sensing systems without additional signal processing, enabling device miniaturization and low power consumption. Herein, pressure sensors with ultrahigh sensitivity and a broad response pressure range are developed with a low-cost, facile method by combining strain-induced percolation behavior and contact area contributions. Because of their special surface structure and strain-induced conductive network formation behavior, these unique pressure sensors exhibit wide sensing range of 1 Pa to 500 kPa, ultrahigh sensitivity (1 × 106 and 3.1 × 104 kPa–1 in the pressure ranges of 1 Pa to 20 kPa and 20–500 kPa, respectively), fast signal response (<50 ms), low detection limit (1 Pa), and high stability over 500 loading/unloading cycles. These characteristics allow the devices to work as e-skins to monitor human pulse signals and finger touch. Moreover, these sensors illustrate precise electrical response to mechanical vibration, bending, and temperature stimuli, which afford the ability of detecting cell phone call-in vibration signals, joint bending, spatial pressure, and temperature distributions, indicating promising applications in next-generation wearable, multifunctional e-skins.

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In this study, the orientation, structure and mechanical performance of a series of uniaxially oriented films based on olefin block copolymers (OBC) have been investigated in terms of the differences in hard block content and draw ratio (DR). Three OBCs with different hard block contents of 35 wt%, 25 wt% and 12 wt% were used. For un-stretched films, a change from close-packed spherulites into tiny crystallites is observed with decreasing hard block content, accompanied by an almost linear decrease in crystallinity.However, the change in mechanical properties does not follow the same path, with obviously higher tensile strength and modulus for OBC-35, but a lower and almost the same tensile strength and modulus for OBC-25 and OBC-12, in spite of the big difference in hard block content and crystallinity between them. For melt-stretched films, the degree of orientation of the amorphous phase is almost the same and slightly increases with the increase in the draw ratio for the three OBCs, disregarding their hard block contents. Crystalline orientation and shish content are much higher for OBC-35, and an obvious increase is seen as the draw ratio increases from 4.95 to 8, corresponding to the sharp increase in Young's modulus and stress. For OBC-25 and OBC-12, similar crystalline orientation and shish content are seen, which increase linearly with draw ratio and are consistent with the linear increase in modulus and stress as the draw ratio increases. Our study demonstrates the importance of the hard block content of OBC to determine the mechanical properties and the response to external stretching. A critical hard block content exists (in this case 35 wt%), above which a strong network is constructed by the hard block crystalline phase, resulting in a higher tensile strength and modulus. This strong network is destroyed as the draw ratio reaches a certain value (herein, 4.95 to 8), leading to an obvious increase in crystalline orientation, as well as a sharp increase in tensile strength and modulus. When the hard block is below the critical content (herein, 25 wt% and 12 wt%), the network constructed by the hard block is weak and less dependent on its content.