This review describes the most recent developments in materials design and the advanced features of ionogels, as well as their emerging biomedical applications.

Water and energy are intimately intertwined, and it is high time to put forth integrated approaches to address the challenges and opportunities of the water–energy nexus. Herein, a novel fluidic photothermal structure integrated with a brine-drenching induced electricity generator is reported for simultaneous clean water and power production. The fluidic photothermal structure is capable of sustaining solar-thermal distillation systems (e.g. interfacial and multi-stage configurations) at high energy conversion efficiency while completely preventing salt formation from occurring in the long-term desalination process, by taking advantage of unidirectional brine fluid transportation. The brine-drenching induced electricity allows immediate power generation with a piece of wet fabric only. Furthermore, the fabric-based energy generator exhibits remarkable programmable properties, and we have also demonstrated that power generation is also achievable with different water sources such as human sweat, groundwater and rainwater, which opens up exciting applications in various fields of energy harvesting and water detection systems, and provides a promising solution for sustainable powering of wearable devices and electronics.

In the era of big data, developing next-generation self-powered continuous energy harvesting systems is of great importance. Taking advantage of fallen leaves’ specific structural advantage gifted by nature, we propose a facile approach to convert fallen leaves into energy harvesters from ubiquitous moisture, based on surface treatments and asymmetric coating of hygroscopic iron hydrogels. Upon moisture absorption, a water gradient is established between areas with/without hydrogel coating, and maintained due to gel-like behaviors and leaf veins for water retention and diffusion restriction, thus forming electrical double layers over the leaf surface and showing capacitance-like behavior for energy charging and discharging. Besides, the specific leaf cell structures with small grooves enabled uniform carbon coatings instead of aggregations, and high electrical conductivity, resulting in 49 μA/cm² and 497 μW/cm³ electrical output, achieving competitive performance with the state-of-art and potential for lower environmental impact compared to other types of energy harvesters.

The rapid proliferation of flexible electronics necessitates the development of self-powered energy harvesting systems with continuous power output and sensing signal monitoring. In this study, inspired by transient voltage output (0.2 volts, 4 days) is proposed by replacing movable water droplets with “confined” moisture, harvested and locked by a hygroscopic polymeric gel with high sorption capacity and rapid sorption-desorption kinetics. Further analysis reveals the capacitive behavior of SEHSI, leading to excellent tactile sensing capabilities with high sensitivity and rapid responsiveness, and humidity and temperature response with robust cyclic stability for over 10,000 cycles. Such all-in-one powering and sensing platforms demonstrate promising application potential in self-powered human-machine interactions, including breath status monitoring, contactless motion detection, and braille detection. Our design establishes a promising approach to developing self-powered energy harvesting and sensing systems for human-machine interfaces.

The application of lithium metal anodes is hindered by safety issues originating from unwanted Li dendritic growth. To address this issue, designing 3D porous Cu current collectors is an effective strategy to modify Li deposition behaviour. However, known fabrication processes for these porous collectors are usually complicated, expensive and non-scalable. There is also lack of investigation into their mechanical strength, which is an important factor for practical applications. Herein, we develop a simple, low-cost and scalable process to fabricate a robust Cu porous framework via extrusion 3D-printing. The 3D-printed Cu framework (3DP-Cu) can well maintain as-built microchannels between filaments even under a high compressive pressure of ∼1.4 MPa, enabling it to host massive Li deposition, prevent Li dendrite growth and mitigate large volume changes during charging/discharging. Therefore, 3DP-Cu achieves a significantly high areal capacity of 20 mA h cm⁻² with uniformly plated Li at a rate of 1 mA cm⁻². Moreover, stable Li plating/stripping behaviour is obtained in symmetric cells even at a high rate of 10 mA cm⁻², owing to the great ability to dissipate high local current densities efficiently by the porous network within filaments. Importantly, robocasting enables structural designs in any desired configurations and dimensions, thereby inspiring the fabrication of customized batteries.