High-performance Droplet Electricity Generator Based on a Lubricant-infused Surface


Student thesis: Doctoral Thesis

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Awarding Institution
  • Zuankai WANG (Supervisor)
Award date6 Jun 2022


Water occupies around 70% of the earth’s area and embodies itself into a wide spectrum of forms ranging from microscale condensates to macroscale rainfall, from discretely falling droplet to continuously streaming flow, from dispersive vapor to cohesive ice. In spite of the large-scale energy exploitation of streaming flow through traditional hydroelectric technology, there are more untapped low-frequency water kinetic energies contained in a wide variety of formats such as mist/moisture, droplet, and wave, because of their intrinsic characteristics including discrete shapes, unconstrained distribution or capricious manifestations. In recent years, triboelectric nanogenerators (TENG), involving the coupling effect of the contact electrification and electrostatic induction, and droplet electricity generator, featuring with the transistor-like architecture, have held promise for the effective collection of the low-frequency water energy due to their simple design, a wide spectrum of material selection, and facile fabrication. However, at present, these low-frequency water energy harvesting technologies still face the dilemma of the unsatisfied scalability and poor stability of the long-standing operations under the practical conditions including the temperature, humidity and salinity. In this thesis, leveraging on the rational design of the dielectric layer and electrode structure, we achieve a cellular water energy harvester, in which a lubricant-armored transistor-like electricity generator is designed as a cellular building block that imparts desirable electrical performance and stability of water energy collection in a wide spectrum of harsh environments, ranging from high salinity to caustic acid-base, from low humidity to high humidity, and from low temperature to room temperature.

First, this thesis summarizes the recent progress of the surface charge-based water energy harvesting technologies, starting from the origin of surface charges and energy conversion methods based on the surface charges. Moving to the practical application of these harvesting technologies, main limitations in previous works are highlighted, which lays a rational foundation for designing advanced water energy harvester

Second, we report a lubricant-armored transistor-like electricity generator (LA-TEG), which enables a stable and efficient water energy harvesting leveraging on the design in marriage of the droplet electricity generator and the slippery lubricant-infused porous surface (SLIPS). The transistor-like electrode design allows for the reversible and efficient transfer of charges during the electricity generation, resulting in a great enhancement of power density by several orders of magnitude over its counterparts with the traditional electrode design. In addition, the slippery and configurable lubricant layer endows an outstanding performance stability of LA-TEG under various harsh conditions including high relative humidity, low temperature, high salinity and even high pH, owing to its capability to rapidly detach water and prevent the adsorption of ions in water.

Third, we discuss the performance optimization methods and scalability of the LA-TEG based on the printed circuit board (PCB) technology. Leveraging on the equivalent circuit model analysis and experimentally demonstrations, we find the mutually exclusive effect of the thickness of SLIPS layer and the salt concentrations in water on the performance enhancement, which finally leads to an optimized electrical performance of LA-TEG. In addition, with a favorable electrode design that is compromised of the transistor-like electrodes and connection circuits, the large-scale integration of LA-TEG units into the cellular water harvester is achieved with the remarkable versality in different formats of water energy harvesting such as the condensate, droplet, flow, and wave.

In summary, this thesis systemically investigated the high-performance droplet electricity generator based on a lubricant-infused surface. Such design exhibits the enhanced electrical performance and remarkable performance stability in various extreme environments. Leveraging on a commercial printed circuit board (PCB) technology, we designed a cellular water energy harvester consisting of variable numbers of LA-TEG units for a large-scale water energy harvesting. We believe that our work will yield important insights to the low-frequency water energy harvesting and therefore spur a wide range of applications.