使用銅網電極製作之可撓式駐極體能量擷取器

Abstract

能量擷取(Energy harvesting)是從環境中的能量源收集可用的能量來做為低功率元件的電源供應，而藉由微機電系統(MEMS)的製程技術，可將能量擷取系統與低功率元件整合。近年來這些低功率元件也被運用在醫療相關領域中，對於需要植入人體的侵入式裝置，若使用電池做為其能量來源，則會有更換不方便等缺點，故對於這些元件而言，使用能量擷取將比使用電池更加適合。人體為一種能量源，人體運動多為非週期性及隨機的運動，而具有可撓性之能量擷取器可貼附於人體，並從人體運動中收集能量做為低功率負載之電源供應。 本論文提出針對人體運動之靜電式駐極體能量擷取器，為了使裝具有可撓性及生物相容性，本論文使用聚二甲基矽氧烷(PDMS)作為基板，並以Parylene C作為駐極體。在本實驗室先前研究成果中，使用濺鍍方式製作之電極經多次變形後，電極易龜裂而造成裝置壽命降低。本論文使用銅網做為電極，其優點除降低製作成本外，更改善電極可靠度不佳的問題。針對不同應用，本論文共製作兩種不同設計的能量擷取器，其不同之處在於電極間格物，第一種設計使用環狀間格物，可針對人體行走及跑步中收集能量，第二種設計使用圓柱陣列間格物，可從人打字中收集能量。在1000 MΩ的負載及下壓頻率為20 Hz的條件下，產生之輸出功率分別為3.15 μW及2.26 μW，功率密度分別為15 μW/cm3及23 μW/cm3。若將能量擷取器實際用於人體運動，兩種設計在1000 MΩ的負載下，使用手指下壓可產生約300 nW的輸出功率，手指彎曲則約為5 nW。

Energy harvesting is the process of scavenging energy from ambient energy sources in environment to serve as power supply for low-power electronics devices. By Micro-Electro-Mechanical System (MEMS) fabrication technology, energy harvesting system can be integrated with low-power devices. For invasive devices in biomedical applications, batteries are discouraged due to its cost of operations for replacement. Therefore, energy harvesting is more suitable then batteries for low-power devices. Human motion which is usually complicated and aperiodic can be an energy source. Flexible energy harvesters can scavenge energy from human motion by attaching them to human bodies, and power up low-power devices. In this thesis, electrostatic flexible electret energy harvesters for human motion are proposed. For flexibility and biocompatibility, the substrate was polydimethylsiloxane (PDMS) and Parylene C was used as electret. In our previous work, the sputtered electrode were prone to cracks upon the deformation of the devices, thus limiting the lifetime. To improve the reliability, flexible electret energy harvesters with embedded copper mesh are proposed. In this thesis, two prototypes of energy harvesters have been fabricated. Prototype I has square spacer of rings and is suitable for harvesting energy from walking. Prototype II has arrays of spacer posts and is suitable for harvesting energy from finger typing. The output power for the two prototypes were 3.15 μW and 2.26 μW, corresponding to power density of 15 μW/cm3 and 23 μW/cm3 at test frequency of 20 Hz with a 1000-MΩ load, respectively. In human motion test, the harvester was attached to a human finger. With a 1000-MΩ load, the output power were approximately 300 nW for finger tapping, and 5 nW for finger bending.