Fabrication of Hybrid Nano/Microstructured Optic and Biosensor Components using Gas-Assisted Hot Embossing and AAO Mold

奈米結構的表面廣泛應用於太陽能聚光板抗反射、生物醫學檢測等。但目前奈米結構模具的製作，大多仰賴電子束或離子束等加工方式，加工時間長且昂貴。本研究結合陽極氧化鋁奈米孔洞模具製作及氣體輔助熱壓成型之技術，於PC薄膜表面製作出奈米結構並探討其於光學及生醫之應用。 本研究製作陽極氧化鋁(AAO)模具，首先以40 V、80 V及180 V的外加電壓獲得100 nm、160 nm及450 nm間距之奈米孔洞，另以時間及酸液濃度來控制孔洞直徑。接著使用氣體輔助熱壓製程將高分子PC薄膜均勻的充填於模具中，調整溫度及壓力可控制充填的深度，利用此複製方式，製作出次波長結構並加以應用於抗反射及生醫檢測。 在光學抗反射的應用上，以氣輔壓印控制奈米結構的高度約1 μm，藉脫模時規則性斷裂形成高約260 nm的尖錐狀結構；光學量測結果顯示，在光波長550 nm處，反射率由原先的8.9 ％降低至2 ％，此錐形次波長結構有抗反射效果。本研究進一步提出創新製程，利用兩次氣輔熱壓方式，先將奈米結構複製於PC，再以此有奈米結構之PC為基材複製微透鏡，可得表面有奈米結構的微透鏡，兼具透鏡光學性質以及奈米結構的抗反射效果，證實此法製作複合微奈米結構之潛力。 本研究另一方向是生醫檢測應用。將不同幾何形狀的AAO模具鍍上一層金膜，再以氣輔熱壓方式將具奈米結構之金膜轉印於PC基材上，於水和空氣兩種介質下測定其穿透率，因環境折射率的改變而導致穿透率的不同，以此特性可應用於生醫感測器。此外，本實驗利用氣輔熱壓方式將AAO結構製作於PC表面，形成間距約100 nm的錐型陣列，將其鍍金並檢測對-巰基苯甲酸(p-mercaptobenoic acid，PMBA)的拉曼散射光譜，由檢測證實此製程所提供之表面具有可放大檢測訊號的能力，達到表面增強拉曼散射(SERS)之效果，可用來判斷不同生物分子結構。Nanostructured surfaces are widely used for anti-reflection and bio-sensing. But the production of nanostructured mold most relies on expensive high-end facilities. This study presents an easy and low-cost approach. Anodic aluminum oxide (AAO) mold and gas-assisted hot embossing process are employed to fabricate the nanostructures on the surface of polycarbonate (PC). They are further used for optical and bio-sensing applications. The alumina oxide membranes with nanoholes of 100 nm, 160 nm and 450 nm in pitches were fabricated via two-step anodization, employing anodization voltage of 40 V, 80 V and 180 V respectively, and the pore size can be controlled by anodization time and concentration of electrolyte. The soften polymeric material can be filled into mold with periodic nanopores by gas-assisted hot embossing process, with the depth of filling determined by embossing temperature and pressure. Sub-wavelength structures (SWSs) can thus be produced. Two applications are investigated in this study. The first is the anti-reflection film. PC film with nanorods of 150 nm in diameter, 160 nm in pitch and 1 μm in height was protruded in the AAO mold. The cone-shaped nanostructures with height of 260 nm were then obtained when the PC film was stripped off from the AAO mold. The PC film with nanocone structures reduces the reflectivity from 8.9 % of a bare film to 2 % of a film with tapered SWSs at the wavelength of 550 nm. This technology is further used to fabricate microlens array with anti-reflective SWSs on it. The nanostructures and microlens array are fabricated on the same PC substrate by hot embossing in sequence. First, AAO template is used as the template for fabricating nanostructures on the PC film by hot embossing. Stainless steel mold of micro-holes array, with 145 μm in diameter and 200 μm in pitch, is then used as the mold to form microlens array. By protrusion of the nanostructured PC film into the micro-holes of the mold, an array of convex microlenses with anti-reflective nanostructures is formed. This proposed technique has proven effective and efficient in fabricating nano/micro hybrid lens array on the polymeric substrate. Another application is the biosensors. AAO molds with nanopores of 70 nm, 150 nm in diameter and 100 nm, 450 nm in pitch are coated with a layer of gold film, then a gas-assisted hot embossing process is used to imprint gold film nanostructure onto polymer (PC) substrates. Since localized surface plasmon resonance (LSPR) taking place in periodic-gold-film-nanostructured surface, the red shift can be detected, based on transmission spectra, when they are immersed in different solutions. In this study, the transmission spectrum in air and water are compared, showing the potential for biosensing applications. Another approach is to fabricate the nanocones on the surface of PC film by protruding the PC into nanopores of AAO and then tearing the PC film off the mold. The pitch of the nanocones is about 100 nm. The nanocones are subsequently coated with gold. When the gold-coated nanocones are immersed in monolayer-foring aqueous solutions of p-mercaptobenzoic acid (PMBA), the surface-enhanced Raman scattering (SERS) spectra is detected, showing that this surface has the function of enhancing the signal of the SERS. This reveals the potential of using this gold-coated periodic nanorod structures for sensing the molecular structure of different organisms based on SERS