Flexible strain sensors occupying a large part of human body detection and wearable electronics, which have a wide sensing range and high sensitivity, are crucial in fully monitoring human motion signals. This study proposed a strategy to construct flexible strain sensors based on the V-groove/wrinkles hierarchical array. The V-groove array was prepared on a polydimethylsiloxane (PDMS) substrate through mold transfer printing. The gold film was sputtered on the prestretching PDMS substrate, and the V-groove/wrinkles hierarchical array was formed after strain release. Compared with the sensors based on single-scale wrinkle structures and a V-groove array, the fabricated strain sensor with the hierarchical array showed high sensitivity (maximum gauge factor up to 2,557.71) and a wide sensing range (up to 45%). In addition, the dynamic characteristics of the sensor were investigated in detail, indicating that the sensor had a fast response (less than 130 ms), a low detection limit (0.1% strain), and good stability (almost no performance loss after 10,000 cycles). In practical applications, the sensor was used to detect sizable physical motion and weak physiological signals, demonstrating great potential application value in human motion detection. This study could provide new ideas for preparing high-performance flexible strain sensors.

enlarge the signal of conventional Raman test, achieve trace detection, and even single-molecule detection. [4] Because of its unique fingerprint peak characteristics, non-destructive testing, fast response, and other advantages, [5,6] it is widely used in environmental monitoring, [7,8] food safety, [9][10][11] biomedicine, and other fields. [12][13][14] So far, there is no clear theoretical model that can explain the complex SERS phenomenon.However, electromagnetic enhancement (EM) and chemical enhancement (CM) are two kinds of SERS mechanisms that are generally accepted by the academic community. [15,16] The EM means that incident laser excites the surface of the precious metal nanostructure to form localized surface plasmon resonance, thereby amplifying the scattering signal. [17,18] The enhancement performance is the best in nanogaps (<10 nm) with small adjacent intervals, so these gaps are called hot spots, [19] which make it possible to detect single molecules. The enhancement factor (EF) of EM can reach 10 6 or higher, which is the dominant factor of signal enhancement. The CM mechanism is to form a chemical bond between adsorbed molecules and the surfaces of SERS substrate, resulting in charge transfer. The EF of CM is generally 10-100, [20] which is much smaller than EM. Meanwhile, the CM effect is often ignored in some experiments, because it just appears when the molecule is in contact with the substrate. [21] In summary, in order to design a high-performance SERS substrate, high-dimensional, and highdensity hot spots distribution must be considered.So far, a variety of SERS substrates have been reported. Most beginners build SERS substrates based on silver (Ag) nanoparticles. [22] Then 1D and 2D structures are introduced, such as nanorods, [23] nanowires, [24] graphene, [25] etc. Currently the most commonly used is the 3D hierarchical structures such as the nanoflowers array. [26][27][28] The ordered 3D structures can expand the distribution of hot spots, so that the SERS substrate has a larger enhancement factor. Besides, when used in practical applications, the uniformity and stability should not be ignored. Therefore, it is not only necessary to consider sufficient hot spots distribution, but also to precisely control the orderliness of the structures. Zhao et al. proposed a strategy to build the flexible SERS substrate, which was achieved by graphene oxide/Ag nanoparticles/pyramidal polymethyl methacrylate. [29] Zhu et al. used polystyrene sphere (PS) single-layer template electrodeposition to prepare a micro-bowl array assembled with Ag nanoparticles Surface-enhancement Raman scattering (SERS) is widely applied in environmental protection, biomedicine, origin traceability, food safety, and other fields as a crucial analysis and detection method. The construction strategy of excellent SERS substrates has always been a research hotspot. In this article, a 3D micro-lens array/wrinkle structures/silver nanoparticles SERS substrate (MLA/WS/AgNPs 3D-SERS) is prepared, which is enlightened by rose peta...

Flexible pressure sensors have been extensively explored for their widespread applications in wearable electronic devices such as medical diagnosis and motion monitoring. In this paper, a facile method is adopted to prepare the ordered hierarchical structure array and then it is applied to improve the performance of capacitive flexible pressure sensors. The results indicate that the pressure sensor based on hierarchical structure array is with high sensitivity (0.382 kPa‐1), fast response and recovery time (26 and 25 ms), and its minimum detection pressure can reach 4 Pa. Besides, the sensor based on hierarchical structure array has also been successfully applied to the dynamic pulse monitoring of the neck, limb movement monitoring, and pressure monitoring in water cup grasping process, which shows high stability and reliability, demonstrating its broad application prospects. This research could provide useful guidance for the preparation and applications of high‐performance flexible pressure sensors.