# Progress of Capillary Flow-Related Hydrovoltaic Technology: Mechanisms and Device Applications
## 3 Device Applications
### Applications for Evaporation-Induced Electricity  
For evaporation-induced electricity, the main applications are focused on power sources and, more recently, hybrid functions of solar evaporation and electricity [30]. We highlight them respectively.  
In 2019, a study introduced a device that integrates water evaporation-induced electricity with a supercapacitor [62], creating a self-charging hybrid power system. This device features a porous carbon-based generator that efficiently converts the energy from water evaporation into electricity, which is then stored in a supercapacitor. The device demonstrated continuous power generation, achieving an open-circuit voltage of approximately 1.5 V and a power density of 50 mW/m\({}^{2}\), making it capable of continuously powering small electronic devices. The integration of these components enables an uninterrupted energy supply, making the device suitable for remote or off-grid applications where conventional power sources are unavailable (Figure 9a). This work highlights the potential of evaporation-induced electricity in enhancing the efficiency and sustainability of energy harvesting technologies, paving the way for its use as a reliable power source in self-powered devices.  
Another study utilized a combination of carbon nanospheres and TiO nanowires to fabricate a smart evaporation-induced electricity generator [63]. This device converts energy not only from the evaporation of water but also from methanol, acetone, and ethanol. Its output is particularly impressive, achieving an open-circuit voltage of up to 1.6 V with water and 2.0 V with methanol, comparable to conventional commercial batteries. By adjusting the evaporation rate and configuring multiple units in series or parallel, the device can reach an open-circuit voltage as high as 20 V. Moreover, its light-responsive properties make it suitable for applications such as self-powered light-control switches and other advanced smart electronics (Figure 9b).  
Evaporation-induced electricity has recently gained attention in the field of solar evaporation. A notable study explored a solar-driven ionic power generation unit that used a composite film made of conductive metal-organic frameworks (MOFs) layered on cellulose  
Figure 9: Applications for evaporation-induced electricity. (**a**) Power source application. Reproduced from ref. [62] with permission from Elsevier, copyright 2019. (**b**) Light\(-\)responsive switch. Reproduced from ref. [63] with permission from the Royal Society of Chemistry, copyright 2019. (**c,d**) Hybrid working mode combining solar thermal energy and water evaporation energy. Reproduced from ref. [64] with permission from the Royal Society of Chemistry, copyright 2021.  
nanofibers [64]. Under light illumination, a thermal gradient significantly enhances the water evaporation rate. By leveraging both ionic thermophoresis and streaming potential, this hybrid device can sustain a voltage output of approximately 1.1 V with a power density of up to 15 W/m\({}^{2}\). The integration of solar power greatly boosts the device's power generation performance (Figure 9c,d). Additionally, the use of MOFs and nanocellulose enhances the device performance while contributing to its lightweight and flexible design.  
In the future, the focus is expected to shift toward hybrid devices that leverage solar evaporation to simultaneously produce purified water and generate electricity. This dual-function approach offers a promising avenue for advancements in sustainable energy and resource management.