A soft piezoresistive sensor with its unique characteristics, such as human skin, light weight, and multiple functions, yields a variety of possible practical applications to skin-attachable electronics, human-machine interfaces, and electronic skins. However, conventional filler-matrix piezoresistive sensors often suffer from unsatisfactory sensitivity or insufficient measurement range, as well as significant cross-correlation between out-of-plane pressure and in-plane extension. Here, a stretchable piezoresistive sensor (SPS) is realized by combining a hierarchically porous sensing element with a multimodulus device architecture via a full 3D printing process. As a result, the sensor exhibits high sensitivity (5.54 kPa −1 ), large measurement range (from 10 Pa to 800 kPa), limited cross-correlation, and excellent durability. Meanwhile, benefiting from the porous structure and mechanical mismatch design, which efficiently distributes the stress away from the sensing element, the device experiences only 7% resistance change at 50% stretching. This approach is employed to rapidly program and readily manufacture stylish, all-in-one, functional devices for various applications, demonstrating that the technique is promising for customized stretchable electronics.

Flexible pressure sensors present great potential in the application of human health monitoring, tactile function of prosthesis, and electronic skin for robotics. These applications require different trade-off between the sensitivity and sensing range, therefore, it is imperative to develop range-specific sensitivities in a single sensor. In this paper, a bioinspired strategy for a resistive pressure sensor using a graded porous material is proposed to measure pressures from several pascals to megapascals. Its fabrication is based on an easily accessible template method. The nest-architecture-based wide-range pressure sensor exhibits adequate sensitivity under an extensive pressure regime (20 Pa to 1.2 MPa). In addition, with rational structural design and subtle engineering of the material properties, the sensor achieves remarkable mechanical stability. To prove the concept, sensors were attached on a bicycle wheel to monitor the tire-pavement pressure and on human skin to detect biosignals such as venous and arterial blood pressure pulses.

In article number https://doi.org/10.1002/adfm.201807569, Zhengchun Peng and co‐workers fabricate a stretchable piezoresistive sensor by 3D‐printing of a multilayered sensing element of a hierarchically porous structure on a pair of 3D‐printed double helix interdigital electrodes on an elastomer substrate. The three layers are composed of the same polymer matrix but with a different modulus. The sensor demonstrates high sensitivity, large measurement range, limited cross‐correlation, stable stretch resistance, and excellent durability.

Epidermal sensing devices, which mimic functionalities and mechanical properties of natural skin, offer great potential for real-time health monitoring via continuous checking of vital signs. However, most existing skin-mounted electronics use a flexible film with high elastic modulus, which hinders physical activity and causes interfacial delamination and skin irritation. The compliance of hydrogel-based devices can firmly conform to complex, curved surfaces without introducing excessive interfacial stresses. However, most hydrogels still suffer from the weakness of stable and reproducible sensing. In this work, we report a skin-friendly epidermal electronic made of a resilient, self-healing, and recyclable polyvinyl alcohol (PVA) hydrogel. The hydrogel is reinforced through a ternary heterogeneous network for good mechanical robustness while maintaining high stretchability and exceptional conformability. Simultaneously, the abundant dynamic hydrogen bonds give the hydrogel rapid self-healing ability. The assembled hydrogel epidermal electronic is able to stably monitor multiple physiological signals as well as sense the strain level of the skin motion and joint bending. The unique, versatile, environmental and biological friendly epidermal electronics will have broad applications in health care, human-machine interface, augmented reality, and so on.

The development of stretchable strain sensors is crucial for the implementation of electronic skins and wearable electronics. Resistive‐type strain sensors are typically composed of an electrically conductive sensing layer coupled to a stretchable substrate. When a sensor is stretched, microstructural changes in the sensing layer lead to a strain‐dependent change in resistance. However, strain sensors with high sensitivity and specificity often suffer from a limited detection range along with reliability issues. Here, a novel strain sensor composed of Ag particles and long‐range entangled carbon nanotubes (CNTs) with a special composite design is proposed, in which a strain‐induced self‐locking effect is introduced at the interface between the CNT film and a percolating network consisting of Ag particle filler. As a result, the sensors achieve significantly enhanced performance such as large stretchability (≥120%), high gauge factor (3990.8), fast response time (<33 ms), and high mechanical durability. A range of wearable applications including radial artery, facial expression, and joint motion monitoring are demonstrated, which range from minute deformation to excessive stretching of the sensor.