Harvesting Energy from Fluid-based Triboelectric Nanogenerator and its Versatile Applications as Mechanical Transducer

Abstract

With the increasing demand of electricity supply and usage of portable electronics in our day to day life, self-powered system has brought a revolutionary change in the recent decades to mitigate the excess pressure on power grid. Following the other nanogenerators like piezoelectric, thermoelectric, triboelectric nanogenerator (TENG) has come up with the utilization of waste mechanical energy into useful power sources. The main advantages of TENG over traditional battery systems are that it doesn’t need to be replaced over time, can continuously harvest energy from the ambient source that can be stored in the capacitors for future supply, very flexible. Triboelectric nanogenerator (TENG) comprises of the contact electrification and electrostatic induction. When two dissimilar materials are bought into physical contact with each other due to electrostatic induction there is a redistribution of charges with the opposite sign on the two surfaces according to tribopolarities. After a while, separation occurs by means of any external mechanical force which induces triboelectricity that can generate a potential drop and drive the electrons to flow between the electrodes attached with the surfaces. TENG has four fundamental modes till now, including, vertical contact-separation mode, lateral sliding mode, singe electrode mode, freestanding sliding mode. In addition, a lot of structures, prototypes and functions have already been reported and are still going on. Mostly triboelectric devices involve solid-solid contact electrification. The charge generation through friction process solely depends on the difference of the ability of the two surfaces to loss or gain electrons. Electrical output can be improved via change of the surface morphological properties in this process. Nevertheless, the performance can be greatly influenced by the air humidity, dust, which causes instability of the output values of the solid-solid TENG without any encapsulation.Also wear abrasion due to physical collision deteriorates the long-term output stability of the TENG. However, liquid-solid contact electrification has demonstrated the capability of stable response with full contact separation process with the counter solid part. The output shows regular behavior for long term application with good wear resistance while using the liquid for contact. In liquidsolid TENG, the liquid can change its shape and mostly work as a positive tribomaterial that exhibit feasibility to be used in flexible and wearable sensor applications. Considering possible advantages of the liquid in TENG application, in this thesis, I’ve taken in account the fluid-structure interaction problem for two cases peristaltic flow in elastic tubing as energy harvester and velocity sensor on the other hand, PDMS based microfluidic platform to sense the pressure and frequencies of the rotary actuator that manipulates the motion discrete liquid column in the channel over thin polymeric film. In the first investigation, a relationship has been developed between the peristaltic laminar flow dynamics while interacting with the PVDF microporous membrane and the generation of voltage and current. Moreover, the described energy harvester can also work as flow sensor. From the second investigation, it is found that, the MEMS device can be effectively used as the transducer to measure the certain frequencies and pressures of rotary actuator