二氧化碳輔助熱融合PMMA接合製程開發研究

Abstract

聚甲基丙烯酸甲酯（polymethyl methacrylate；PMMA），具有高透明度、低廉、易成型、良好生物相容性等優點，常用於製作微流體元件。本論文主要在開發PMMA更有效、更低溫的接合技術。 傳統熱融合接合需加熱至玻璃轉移溫度以上，易破壞微結構；加上傳統以壓板施壓，中心壓力比邊緣大，施壓不均造成殘留應力太大。而有機溶劑接合，需塗佈清除有機溶劑，易留下雜質或傷損微結構。本研究利用二氧化碳為PMMA氣體溶劑及氣體等向均壓施壓之特性，降低PMMA接合溫度，並全面均勻施壓。 經實驗證實，利用二氧化碳對分子鏈糾纏程度鬆散的表面有較佳的促進移動性效果，促使聚合物表面分子鏈穿越接合面，在近室溫下（40 ℃）即具接合效果（強度619 kPa, 接合面積34.76 %）。本製程成功在低於玻璃轉移溫度下（80 ℃）完成微流道元件接合，並維持良好的微結構特徵。 本研究進一步控制二氧化碳滲入與排氣時間方式，開發兩段式二氧化碳輔助熱融合接合製程，使板材獲得均勻收縮；實驗結果顯示，兩段式二氧化碳輔助製程確實可大幅提昇平坦度，並有效增加強度（700 kPa）與接合面積（86.87 %）。 本研究更進一步藉旋塗PMMA甲苯溶液於接合面，利用此表面層增加分子鏈擴散數量，並配合兩段式二氧化碳輔助熱融合接合製程，成功在低於玻璃轉移溫度下完成接合，並大幅提昇接合強度至860 kPa。

Poly-methyl methacrylate (PMMA), which has adventages of high optical transmittance, low-cost, simple fabrication and excellent biocompatibility, is commonly used in manufacturing microfluidic device. This thesis is devoted to the development of effective low-temperature PMMA bonding technology. Traditional thermal fusion bonding must heat the PMMA to above the glass transition temperature, which may distort the microstructures and induce residual stress. In addition, the pressure distribution is not uniform when the substrates are pressed by hot platens. On the other hand, organic solvent bonding comprises coating and removing solvent, which may induce impurities and harm the microstructure. This research uses carbon dioxide (CO2) as gas solvent and as pressuring agent as well. The bonding temperature thus is lowered and the pressing pressure becomes uniform. A bonding area of 34.76 % and bonding strength of 619 kPa have been achieved even the PMMA plates are bonded at a temperature as low as 40 ℃. This bonding process has been successfully applied to the packaging of microchannel device with processing temperature below the glass transition temperature (80 ℃). Besides, in this study an innovative two-stage CO2-assisted thermal fusion bonding process has been developed which takes the soaking and releasing times of CO2 into account. The experimental results shows that this new process significantly enhances the flatness after bonding process and increases bonding area to 86.87 % and bonding strength to 700 kPa. Furthermore, by coating a layer of PMMA solution on bonding surface, the diffusion number of chain increases, and thus increases the bonding strength up to 860 kPa with the two-stage CO2-assisted process.