壓電式微液珠制控平台之設計與製作

Abstract

利用表面聲波制動微液珠之微流道晶片是近幾年相當受重視之研究課題，經由指叉式電極所激發出的表面波對液珠內部造成擾動來驅動液珠，當使用斜交指指叉式電極當驅動源更可達到多重道微流晶片之功能，且一個合乎實用的實驗室晶片必須要擁有自動化特點。 本文結合斜交指叉式(SFIT)表面聲波元件之驅動與偵測兩項功能，配合圖控程式(LabVIEW) 來完成在二維全疏水平台上自動控制微液珠的驅動路徑、定點停滯以及自動轉彎和混合。文中針對雙水珠在SFIT之頻譜的上位置偵測做模擬，探討兩水珠之間距大小對不同的電極交叉長度(Aperture)之設計在頻譜偵測上的關係，以做為控制程式撰寫之參考依據。實驗中並針對液珠驅動時，頻率對最小驅動能量的關係做探討；以及對驅動時間以及驅動波源形式對水珠蒸發影響做探討，並針對此現象提出降低液珠蒸發的方法。為了增加三氯矽甲烷(OTS)疏水膜在壓電基材上的鍵結能力，以提升疏水薄膜的品質，本研究亦於微液珠驅動元件之微機電製程中，在鈮酸鋰(LiNbO3)基材上利用化學輔助氣相沉積(PECVD)系統製作一層厚度約200nm二氧化矽(SiO2)薄膜。 本研究之成果使SFIT微液珠驅動平台得以發展成為一完整的微液珠自動驅動元件，以節省運作時間和繁瑣人力。且無需利用親水點設計來控制水珠定點，以降低因多次檢測造成的交叉汙染影響。

Using surface acoustic wave (SAW) to detect and actuate micro droplet in a two dimensional platform is topic of current research interest. In the method, IDT is utilized to excite SAW and to drive the micro-droplet. By using slanted finger interdigital transducer (SFIT), multi-channel microfluidic becomes possible. In the present study, we combine the detection and actuation of micro droplets on a single device using SFIT. A LabVIEW program was written and used to automate the maneuvering and mixing of micro droplets on a two dimensional hydrophobic platform. This setup enables us to precisely drive multiple micro droplets onto predetermined location for mixing and through this automation decrease the process time of this complex process. Based on simulations of the frequency response of SFIT with two droplets onboard, we analyzed the relation between the different aperture design and the sensitivity of the device at determining the distance between the two droplets. In the experiments, the relationship between the actuation frequency and the minimum actuation power were investigated. We also studied the actuation time and actuation waveform that minimizes droplet evaporating. To increase the binding affinity between the OTS molecule and the substrate, creating a high quality hydrophobic film for our device, a 200 nm thick silicon oxide layer was deposited on the substrate. We note that results of this study can serve as an important reference for developing two dimensional micro droplet controlling device.