Hydrogels, as a series of three-dimensional, crosslinked, hydrophilic network polymers, exhibit extraordinary properties in softness, mechanical robustness and biocompatibility, which have been extensively utilized in various fields, especially for electronic devices. However, since hydrogels contain plenty of water, the mechanical and electrochemical properties are susceptible to temperature. The thermal characteristics of hydrogels can significantly affect the performance of flexible electronic devices. In this review, recent research on the thermal characteristics of hydrogels and their applications in electronic devices is summarized. The focus of future work is also proposed. The thermal stability, thermoresponsiveness and thermal conductivity of hydrogels are discussed in detail. Anti-freezing and anti-drying properties are the critical points for the thermal stability of hydrogels. Methods such as introducing soluble ions and organic solvents into hydrogels, forming ionogels, modifying polymer chains and incorporating nanomaterials can improve the thermal stability of hydrogels under extreme environments. In addition, the critical solution temperature is crucial for thermoresponsive hydrogels. The thermoresponsive capacity of hydrogels is usually affected by the composition, concentration, crosslinking degree and hydrophilic/hydrophobic characteristics of copolymers. In addition, the thermal conductivity of hydrogels plays a vital role in the electronics applications. Adding nanocomposites into hydrogels is an effective way to enhance the thermal conductivity of hydrogels.

The rapid development of micro/nano systems promotes the progress of micro energy storage devices. As one of the most significant representatives of micro energy storage devices, micro hydrogen fuel cells were initially studied by many laboratories and companies. However, hydrogen storage problems have restricted its further commercialization. The γ-graphdiyne (γ-GDY) has broad application prospects in the fields of energy storage and gas adsorption due to its unique structure with rigid nano-network and numerous uniform pores. However, the existence of various defects in γ-GDY caused varying degrees of influence on gas adsorption performance. In this study, Lithium (Li) was added into the intrinsic γ-GDY and vacancy defect γ-GDY (γ-VGDY) to obtain the Li-GDY and Li-VGDY, respectively. The first-principles calculation method was applied and the hydrogen storage performances of them were analysed. The results indicated that the best adsorption point of intrinsic γ-GDY is H2 point, which located at the centre of a large triangular hole of an acetylene chain. With large capacity hydrogen storage, doping Li atom could improve the hydrogen adsorption property of intrinsic γ-GDY; meanwhile, vacancy defect inspires the hydrogen storage performance further of Li-VGDY. The mass hydrogen storage density for Li₂H₅₆-GDY and Li₂H₅₆-VGDY model were 13.02% and 14.66%, respectively. Moreover, the Li₂H₅₆-GDY and Li₂H₅₆-VGDY model had same volumetric storage density, with values that could achieve 5.22 × 10⁴ kg/m³.

Mini-grooved flat heat pipe (MGFHP) possesses the advantages of high compactness, no mechanical component, super thermal conductivity, and excellent temperature uniformity, which can meet the demand for electronic devices efficiently cooling. In this research, visual and heat transfer experiments were performed to investigate the flow and thermal characteristics inside the MGFHP. Fluid flow and distribution are observed to be quite different in the MGFHP containing different working fluids, which is affected by the physical properties of working fluid, the surface state of the grooved wick, and limited working space. Additionally, the input heat, working fluid type, filling ratio, and wettability obviously affect the thermal conductivity and temperature uniformity of the MGFHP. The deionized water-filled MGFHP possesses lower thermal resistance and higher heat transfer capacity than anhydrous ethanol or hexane filled MGFHP, especially for the copper oxide MGFHP filled with deionized water with a filling ratio of 1.0. Thermal resistance, maximum temperature, and temperature nonuniformity at the condensation section of deionized water-filled copper oxide MGFHP are lower than those of the original copper MGFHP by 31.1%, 3.7 °C, and 0.11 °C for the anhydrous ethanol filled MGFHP and 34.4%, 3.1 °C, and 0.13 °C for the hexane filled MGFHP, respectively.

Mini-grooved flat heat pipe (FHP) is an efficient approach to cool the electronics within small space. As it was hard to measure the flow and thermal characteristics inside the FHP, a novel three-dimensional model was set up to couple velocity, pressure, temperature, and mass transport inside the FHP, anticipating understanding the working mechanisms of FHP filled with different working fluids under transient and steady states. Temperature-dependent physical properties of working fluid and simulated thermal conductivity of wick were employed. The numerical results were validated by experiment with the maximum deviations in thermal resistance and maximum temperature of 17.9% and 5.0%, respectively. It was found that working fluid types, properties and input heat affected the FHP performance. The deionized water filled FHP shows more excellent thermal characteristics. Under input heat of 10 W, the thermal resistance, maximum temperature, and temperature nonuniformity of deionized water filled FHP were numerically lower than those of anhydrous ethanol filled FHP by 48.1%, 11.5% and 56.4%, and lower than those of hexane filled FHP by 54.4%, 14.3% and 62.6%, respectively. However, the starting performance of deionized water filled FHP is comparatively poorer. FHP filled with anhydrous ethanol or hexane is more appealing for electronics cooling.

Combining biomass co-firing with oxy-fuel combustion is a promising Bioenergy with Carbon Capture and Storage (BECCS) technology. It has the potential to achieve a large-scale reduction in carbon emissions from traditional power plants, making it a powerful tool for addressing global climate change. However, mercury in the fuel can be released into the flue gas during combustion, posing a significant threat to the environment and human health. More importantly, mercury can also cause the fracture of metal equipment via amalgamation, which is a major risk for the system. Therefore, compared to conventional coal-fired power plants, the requirements for the mercury concentration in BECCS systems are much stricter. This article reviews the latest progress in mercury control under oxy-fuel biomass co-firing conditions, clarifies the impact of biomass co-firing on mercury species transformation, reveals the influence mechanisms of various flue gas components on elemental mercury oxidation under oxy-fuel combustion conditions, evaluates the advantages and disadvantages of various mercury removal methods, and finally provides an outlook for mercury control in BECCS systems. Research shows that after biomass co-firing, the concentrations of chlorine and alkali metals in the flue gas increase, which is beneficial for homogeneous and heterogeneous mercury oxidation. The changes in the particulate matter content could affect the transformation of gaseous mercury to particulate mercury. The high concentrations of CO₂ and H₂O in oxy-fuel flue gas inhibit mercury oxidation, while the effects of NO_x and SO₂ are dual-sided. Higher concentrations of fly ash in oxy-fuel flue gas are conducive to the removal of Hg⁰. Additionally, under oxy-fuel conditions, CO₂ and metal ions such as Fe²⁺ can inhibit the re-emission of mercury in WFGD systems. The development of efficient adsorbents and catalysts is the key to achieving deep mercury removal. Fully utilizing the advantages of chlorine, alkali metals, and CO₂ in oxy-fuel biomass co-firing flue gas will be the future focus of deep mercury removal from BECCS systems.