Differentiated Ionic Electroresponse of Asymmetric Bio‐Hydrogels with Unremitting Power Output

Abstract

Cytomembranes with efficient ionic selectivity and energy circulation, essential for biological activities in multicellular organisms, are a source of inspiration for man‐made biomedical devices. However, current man‐made soft systems mainly imitate simple and passive cytomembranes behaviors, restrained by the grand challenge that lies at the meeting point of synchronous engineering of both (dynamic) ionic selectivity and (passive) transcellular‐like potential in one structure. Here a dynamically differentiated ionic electroresponse and passive incessant power output of an asymmetric bio‐hydrogel constructed using a simple self‐propagative flow approach are reported. The unprecedented freely formed p and n analogue hydrogels yield a transcellular‐like potential (110–200 mV) in response to diverse stimuli—where the cathode or anode is capable of perceivable electroresponse to water and/or salt media, respectively. A single hydrogel can generate an output power density of 135–190 mW m−2 superior to most bio‐inspired soft and/or green power sources. The scalable manufacturing and proof‐of‐concept demonstration elucidate the feasibility of mobilizing passive and dynamic behaviors in one structure. This work has the potential for realizing high‐performance soft power sources in parallel to electrostimulation for neural excitation/inhibition, extending into the previously inaccessible region of biomedical applications.

Electrically driven hydrogel actuators: working principle, material design and applications

“…78,79 Most natural hydrogels exhibit a certain degree of ionization in water, rendering them electrically responsive. Notable natural hydrogels employed in electrically driven applications include chitosan, 72,80 silk fibroin, 81,82 gelatin, 83,84 cellulose, 85,86 alginate, 87,88 agarose, 89 and dual network hydrogels formed from these materials in combination with each other or synthetic polymers. 90 For instance, Sun et al fabricated chitosan/ PEG fibers through a wet spinning process from a mixed chitosan and PEG solution, investigating the influence of factors such as fiber diameter, crosslink density, electric field strength, pH, and ionic concentration on the electrically driven properties of the fibers 91,92 Kim et al reported a chitosan/ P(HEMA) hydrogel system featuring an interpenetrating polymer network structure, demonstrating rapid deformation capabilities with a bending angle of 351 achieved in 18 seconds at a voltage of 10 V. 70 Purely natural polymer-based hydrogels exhibit superior biocompatibility and degradability compared to synthetic counterparts.…”

“…Fig.4Main molecular structure of E-hydrogel actuators including homopolymers, copolymers and naturally derived polymers 65,[69][70][71][72][73]. …”

Ion‐Diode‐Like Heterojunction for Improving Electricity Generation from Water Droplets by Capillary Infiltration

“…Moreover, the measured J-V curves also exhibit rectification behavior, which weakens with ion migration and water evaporation. [28][29][30] As the current response slowly decreases after reaching its peak due to water evaporation and saturation of ionic gradients, the rectification also weakens; therefore, we recorded the J-V and current-time curves of the WDHEG under a squarewave bias voltage (from +2 to −2 V) after operating for different times (Figure 3e,f). As shown in Figure 3e, ion rectification can be observed in the formed diode-like heterojunction, where the current at a positive voltage (+2 V) is considerably larger than that at a negative voltage (−2 V).…”

“…[28] Recently, an anion-cation heterostructured hydrogel with a current rectification ratio reaching 4.5 has been designed for moisture electricity generation; the hydrogel can adjust the ion gradients through ion rectification to achieve a long-term, uninterrupted output, with a voltage of 0.1 V and current of 0.4 μA. [29,30] Several HEGs based on the streaming potential and simultaneous use of asymmetric structures (e.g., heterojunctions) have been reported; however, their mechanism remains unclear. [18,24,30,31] Herein, we report a high-performance WDHEG induced by capillary infiltration.…”

Biomimetic Dual Absorption–Adsorption Networked MXene Aerogel-Pump for Integrated Water Harvesting and Power Generation System

“…Traditional commercial sorbents, such as silica gels and zeolites, commonly exhibit a low water collection capacity and require high energy consumption for water release. Tremendous efforts have been conducted to develop high-performance water harvest materials such as inorganic salts, metal–organic frameworks (MOFs), aerogels, natural wood, and hydrogel composites hygroscopic salts. , Although such materials provide constructive concepts for moisture capture, their poor cyclic durability and low water-releasing performance still hinder their broad applications, such as desiccants for dehumidification. Two key points should be considered for designing a high-performance atmospheric moisture harvester: (1) desiccants should provide strong attraction to moisture with favorable exposed active area to the air to water molecules capture continuously; (2) on the contrary, the interaction between water and desiccants should be weakened when releasing the captured moisture. , Therefore, the ideal water harvesters should exhibit both highly hygroscopic properties and facilitate concurrently efficient water transportation from the surface to the internal space concurrently.…”