With the increasing demand for small and portable electronic devices, new energy conversion systems that can harvest energy from body motion and ambient environment are needed. Triboelectricity has recently become promising among the various energy conversion mechanisms because triboelectric devices can be small, flexible, and portable.   These devices can also harvest small-magnitude and low-frequency mechanical energy that is otherwise wasted in our daily life, such as human motion, and low-frequency vibrations. Fundamentally, triboelectricity is contact electrification induced when two materials with different surface work functions are brought into contact with each other. The triboelectric output performance is closely related to the materials’ properties employed. Material properties, such as dielectric permittivity, electrical conductivity, and dielectric loss, in addition to geometric parameters and mechanical properties, such as relative compliance and elastic limit, have been shown to impact the response. In this study, the effect of electrical conductivity and surface contact area on the electrical output of a triboelectric device is investigated both experimentally and computationally. 

 

Polymers serve as the predominant choice for triboelectric materials owing to their superior dielectric properties and favorable mechanical properties. Among the polymeric materials that have good triboelectric behavior is polydimethylsiloxane (PDMS) which is used as the matrix material in this study.  It is inexpensive, easy to fabricate, biocompatible, and its triboelectric polarity is already known. The electrical conductivity of PDMS is tuned by adding different weight percent of carbon nanotube (CNT). Experiments are conducted using a vertical contact and separation mode with Teflon as the complimentary contacting material. The open circuit voltage (V~oc~) and short circuit current (I~sc~) of the CNT-PDMS/Teflon system are measured with an electrometer and a picoammeter respectively. The relationship between electrical conductivity and the triboelectric output performance is obtained by correlating the V~oc ~and I~sc ~with different weight percent CNT-PDMS materials. In addition, the output performance is also related to the contact area of the two contacting materials. The maximization of the true contact area between a pair of materials should yield the highest electrical output. In order to increase the true contact area between the two materials, material surfaces are embedded with various geometric structures. The introduction of these structures may either augment or reduce the true contact area depending on an array of geometrical parameters and mechanical properties. In this study, the dependence of the true contact area on these aspects is investigated computationally. This study aims to contribute a deep understanding of the effect of material’s electrical conductivity and contact area on the performance of triboelectric devices and paves the way to fabricating new material for high power output and stable triboelectric performance.


On the Effects of Electrical Conductivity on the Triboelectric Behavior of a PDMS-Based Composite Material

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

SMASIS2020 - Virtual Conference

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.