PDMS在微機電系統中的應用

Abstract

近年來，PDMS相關的研究越來越頻繁了，不論是微流道網路，或者是薄膜、微閥門，PDMS都展現了製造的方便性以及優良的機械特性。本每研究中將會提出兩個使用PDMS來製做的元件，首先是一個在上下電極板中包含有一個PDMS結構的軸向靜電致動器。這種致動器使用PDMS的彈性，當一個PDMS的結構受到上下電極板的擠壓，它會產生一個和壓縮量成非線性的回復力。靜電力的非線性特性會讓一個軸向的靜電力發生pull in的現像，而讓可移動的距離只有原間隙的1/3。但是利用這一個非線性的回復力可以增加軸向致動器的可移動距離。本研究中致動器的可移動距離達到了原間隙的54%。 第二個元件是使用PDMS製做懸臂樑。和一般微機電常用的結構層材料polysilicon相比，PDMS的楊氏系數大約比的小了5個數量級，所以這種元件的驅動電壓會很小。此外，適合PDMS的製程會能夠經由在製做此元件的過程中發展出來。然而在本研究中並沒有完成此一元件的製做，PDMS本身的楊氏系數小而讓它不容易懸浮。但是在本研究中以經成功的蝕刻定義了一層旋塗的PDMS膜。

PDMS is a frequently used material in MEMS applications. Whether the systems such as microfluidic networks or the devices such as membranes and valves, PDMS is easy to fabricate and exhibit excellent mechanical properties. In this study, PDMS will be used to fabricate two devices. The first one is a gap-closing actuator with PDMS posts placed between the electrodes. Such a device employs the elasticity of PDMS. When a small PDMS post is compressed by two parallel plates, it undergoes a large deformation and therefore provides elastic restring force that is nonlinear with the compressive displacement. The nonlinear elastic restoring force of the PDMS post will be used to balance the nonlinear electrostatic force. Because the elastic restoring force is nonlinear, the gap-closing actuator can achieve a larger controllable displacement than the actuator with linear elastic structure. The measured data of this device reveal that the nonlinear elastic restoring of the PDMS posts can extend the controllable displacement of a gap-closing actuator. The controllable displacement achieves the 54% of the original gap. The second device is PDMS cantilever beams. The Young’s modulus of PDMS is about 5 orders less than the polysilicon, which is a common by used structure material in MEMS. Therefore, to actuate such a device, the applied voltage will be much less. Besides, by fabricating such a device, the properties of PDMS can be obtained and the processes suitable for PDMS fabrication will be developed. But the results of the fabrication process reveal that the stiffness of PDMS is too small to suspend itself. However, processes to pattern a spun on PDMS layer was developed successfully.