Water wave energy exhibits great potential to alleviate the global energy crisis. However, harvesting and utilizing wave energy are challenging due to its irregularity, randomness, and low frequency. Triboelectric nanogenerators (TENGs) have gained significant attention for harvesting wave energy with high efficiency. This study presents a novel ellipsoidal, pendulum-like TENG integrating both liquid-liquid (L-L) and solid-solid (S-S) triboelectricity (LS-TENG). This innovative design enables continuous wave energy harvesting and self-powered marine environment monitoring under various conditions, including temperature, humidity, and light intensity. The binary immiscible liquids within the LS-TENG’s inner soft balloon create dynamic, and self-adjustable L-L contact interfaces, significantly increasing the L-L contact area and enhancing L-L contact electrification (CE). The unique self-adaptive, soft S-S contact increases the S-S contact area compared to traditional hard point contact, better adapting to the irregular movements of waves and promoting efficient S-S CE. The LS-TENG achieves highly efficient wave energy harvesting by coupling L-L and S-S CE. Furthermore, the unique soft contact design protects the S-S interfaces from mechanical wear and damage during long-term work. The LS-TENG's novel structure provides an innovative and effective way for water wave energy harvesting.

Computer vision techniques are real-time, immersive, and perceptual human-computer interaction technology. Excellent display effect, dynamic surface flexibility, and safe bio-adhesion are essential for various human–computer interaction applications, such as metaverse interfaces, skin-like sensors, and optoelectronic medical devices. However, realizing the flexible matching of inorganic optoelectronic devices and organisms remains a grand challenge for current display technologies. Here, we proposed a novel strategy by combining the optoelectronic advantages of inorganic micro light emitting diode (micro-LED) display and the extraordinary mechanical/biological compatibility of organic materials to overcome this challenge. A highly elastic (greater than 2000% strain), highly transparent (94% visible light transmittance), biocompatible conductive hydrogel composite electrode layer was fabricated. For the first time, we realized the on-chip electrical interconnection of 4900 LED units to form a blue-green light display patch with high resolution (264 PPI), low power consumption (4.4 mW) and adaptive surface attachment. This work demonstrates an integrated scheme and potential applications of flexible high-resolution microdisplays, such as wearable full-color micro-LED smart curved display devices and conformable biomedical monitoring systems.

Visualization is a direct, efficient, and simple interface method to realize the interaction between human and machine, whereas the flexible display unit, as the major bottleneck, still deeply hinders the advances of wearable and virtual reality devices. To obtain flexible optoelectronic devices, one of the effective methods is to transfer a high-efficient and long-lifetime inorganic optoelectronic film from its rigid epitaxial substrate to a foreign flexible/soft substrate. Additionally, piezo-phototronic effect is a fundamental theory for guiding the design of flexible optoelectronic devices. Herein, we demonstrate a flexible, stretchable, and transparent InGaN/GaN multiple quantum wells (MQWs)/polyacrylamide (PAAM) hydrogel-based light emitting diode coupling with the piezo-phototronic effect. The quantum well energy band and integrated luminous intensity (increased by more than 31.3%) are significantly modulated by external mechanical stimuli in the device. Benefiting from the small Young's modulus of hydrogel and weak Van der Waals force, the composite film can endure an extreme tensile condition of about 21.1% stretching with negligible tensile strains transmitted to the InGaN/GaN MQWs. And the stable photoluminescence characteristics can be observed. Moreover, the hydrogen-bond adsorption and excellent transparency of the hydrogel substrate greatly facilitate the packaging and luminescence of the optoelectronic device. And thus, such a novel integration scheme of inorganic semiconductor materials and organic hydrogel materials would help to guide the robust stretchable optoelectronic devices, and show great potential in emerging wearable devices and virtual reality applications.

Conductive hydrogels have become one of the most promising candidates for flexible electronics due to their excellent mechanical flexibility, durability of deformation, and good electrical conductivity. However, in real applications, severe environments occur frequently, such as extremely cold weather. General hydrogels always lack anti-freeze and anti-dehydration abilities. Consequently, the functions of electronic devices based on traditional hydrogels will quickly fail in extreme environments. Therefore, the development of environmentally robust hydrogels that can withstand extremely low temperatures, overcome dehydration, and ensure the stable operation of electronic devices has become increasingly important. Here, we report a kind of graphene oxide (GO) incorporated polyvinyl alcohol-polyacrylamide (PVA-PAAm) double network hydrogel (GPPD-hydrogel) which shows excellent anti-freeze ability. The GPPD-hydrogel exhibits not only good flexibility and ultra-high stretchability up to 2,000%, but ensures a high sensitivity when used as the strain sensor at −50 °C. More importantly, when serving as the electrode of a sandwich-structural triboelectric nanogenerator (TENG), the GPPD-hydrogel endows the TENG high and stable output performances even under −80 °C. Besides, the GPPD-hydrogel is demonstrated long-lasting moisture retention over 100 days. The GPPD-hydrogel provides a reliable and promising candidate for the new generation of wearable electronics.