Hydrovoltaic Nanogenerators for Self‐Powered Sweat Electrolyte Analysis

Abstract

Human sweat comprises various electrolytes that are health status indicators. Conventional potentiometric electrolyte sensors require an electrical power source, which is expensive, bulky, and requires a complex architecture. Herein, this work demonstrates an electric nanogenerator fabricated using silicon nanowire (SiNW) arrays comprising modified carbon nanoparticles. The SiNW arrays platform is demonstrated as an effective self‐powered sensor for sweat electrolyte analysis. It has been shown that an evaporation‐induced water flow in nanochannels can yield an open‐circuit voltage (Voc) of 0.45 V and a short‐circuit current of 10.2 µA at room temperature as a result of overlapped electric double layers. The electrolyte in the water flow results in a Voc decrease due to the charge shielding effect. The Voc is inversely proportional to the electrolyte concentration. The fabricated hydrovoltaic device shows the capability for sensing electrolytes in human sweat, which is useful in evaluating the hydration status of volunteers following intense physical exercise. The device depicts a novel response mechanism compared to conventional electrochemical sensors. Furthermore, the hydrovoltaic device shows a maximum output power of 1.42 µW, and as such has been successfully shown to drive various electronic devices including light‐emitting diodes, a calculator, and an electronic timer.

A Transpiration-Driven Electrokinetic Power Generator with a Salt Pathway for Extended Service Life in Saltwater

“…Nano hydro technology offers a viable approach to tap into this resource for clean and renewable electricity generation. This technology capitalizes on the inherent self-generating activity at the interface of conducting nanomaterials, allowing nano hydroelectric devices to convert nanoscale hydrodynamic energy into electrical energy. , The electrical energy generated hinges on electrodynamic effects: when water interfaces with nanomaterials, it triggers adsorption and diffusion phenomena within the material, forming an electrical double layer (EDL) at the water–solid interface. , In the nanochannel, the overlapping EDL causes a separation of positively charged ions (e.g., H + ) and negatively charged ions (e.g., H 3 O – ), creating a gradient distribution and, consequently, a potential difference. , This potential difference manifests between the wet and dry zones of the device, where ion adsorption occurs, leading to electron migration from the wet zone to the external circuit and eventual flow to the dry zone, thereby generating an electron flow . Simultaneously, water evaporation on the nanomaterial encourages water flow through nanochannels via capillary forces, maintaining wetting asymmetry and sustaining potential differences, akin to transpiration in plants …”

“…15,16 The electrical energy generated hinges on electrodynamic effects: when water interfaces with nanomaterials, it triggers adsorption and diffusion phenomena within the material, forming an electrical double layer (EDL) at the water−solid interface. 13,17 In the nanochannel, the overlapping EDL causes a separation of positively charged ions (e.g., H + ) and negatively charged ions (e.g., H 3 O − ), creating a gradient distribution and, conse-quently, a potential difference. 18,19 This potential difference manifests between the wet and dry zones of the device, where ion adsorption occurs, leading to electron migration from the wet zone to the external circuit and eventual flow to the dry zone, thereby generating an electron flow.…”

Liquid–Solid Triboelectric Nanogenerator Arrays Based on Dynamic Electric‐Double‐Layer for Harvesting Water Wave Energy

“…[24][25][26] The EDLs create strong electric fields and contain huge energy. [26] Recently, based on the EDL theory, electricity has been generated from various dynamic processes of water including flowing, waving, dropping and evaporating, [26][27][28][29][30] in the form of liquid-solid TENGs, droplet generators, evaporation generators or others. These methods can avoid the problems of fully enclosed TENGs for water wave energy harvesting, but the output performance is still relatively low now.…”

Enhancing energy extraction from water microdroplets through synergistic electrokinetic and galvanic effects

“…Water evaporation power generation technology is thus promising for diverse applications, such as self-powered sensors and exible wearable power generation. [12][13][14][15] Notably, the immense potential for generating green electricity through water evaporation has fueled the development of various types of evaporative power generation materials, including biomass, 16,17 metal oxide, 18,19 and carbon-based materials. 20,21 Carbon black (CB) is a particularly attractive material for water evaporation power generation due to its abundance, cost-effectiveness, and facile preparation process.…”

“…Water evaporation power generation technology is thus promising for diverse applications, such as self-powered sensors and flexible wearable power generation. 12–15…”