基於實驗、理論和有限元素法增加雷射誘導前向轉移於金屬積層製造之附著力與電特性

Abstract

近年來，雷射誘導前向轉移 (Laser-induced forward transfer, LIFT) 已成為一種廣泛使用的製造技術。這種先進的一步式、非接觸式、省時且經濟高效的方法已在各種電子、生物和化學應用的各種感測器的製造中得到普及。基於 LIFT 的製程技術具有高分辨率和靈活性等優點，因此，使用LIFT在積層製造上之各種應用中有著巨大的潛力。LIFT幾乎有能力轉移任何材料，可利用這種技術可以製作出各種具有複雜細節的結構。本論文聚焦在使用 LIFT 對金屬進行積層製造以展示未來的應用，因此，利用 LIFT 來轉移銅 (Cu)、銀 (Ag) 和鉑 (Pt)等金屬。 先期實驗顯示，沉積金屬材料和接收基板之間有低的附著力；沉積結構中的不連續性降低了導電率，再者，Ag 和 Pt 薄膜的脆性和不同材料特性的差異使得通過 LIFT 進行的積層製造極具挑戰性。因此，在本論文中作出了許多實驗來提高轉移質量。例如，使用雷射表面紋理化 (Laser surface texturing, LST) 和光聚合固化技術將表面粗糙度引入接收基板。此外，探討了在低壓和大氣環境中進行LIFT實驗。最後，LIFT轉移過程是根據實驗和相關表徵來進行優化，包括SEM、EDS、XRD 和電阻測試，以了解沉積材料作為軟性感測元件電極的可行性。此外，本論文也使用有限元素法 (Finite element method, FEM)來分析 LIFT 轉移過程，以有效地將實驗參數優化。最後，使用已建立的理論和FEM結果進行了能量研究，以實現影響 LIFT 過程的主要物理現象。

Laser-induced forward transfer (LIFT) has been a widely used manufacturing technique in recent times. The novel one-step and contactless method have gained popularity in the manufacturing of a wide range of sensors for various electronic, biological, and chemical applications. Nevertheless, LIFT based printing has advantages such as high resolution and flexibility. Additive manufacturing has shown significant potential in various applications. LIFT has the ability to manufacture almost any materials; therefore, utilizing such a process in additive manufacturing enables printing of a wide range of materials with intricate details. This research concerns about the additive manufacturing of metals via LIFT to demonstrate future applications. Therefore, this research utilizes LIFT for printing copper (Cu), silver (Ag) and platinum (Pt). However, experimental evidence has shown weak adhesion between the deposited material and receiver substrate. Moreover, the discontinuities in the deposit structure reduces the conductivity. In addition, the brittle nature and difference in distinct material properties of Ag and Pt thin films make additive manufacturing via LIFT extremely challenging. Therefore, numerous efforts are made in this work to enhance the printing quality. For instance, surface roughness is introduced to the receiver substrate using laser surface texturing (LST) and vat photopolymerization. Furthermore, conducting LIFT in low pressure and ambient environments are investigated. Simultaneously, the effects of the aforementioned efforts shall be investigated on soft and hard polymers with variable thickness based on their shore hardness. Finally, the LIFT process shall be optimized based on the aforementioned experiments and relevant characterizations. Scotch tape tests are carried out for determining the adhesion strength. Further characterizations include SEM, EDS, XRD and conductivity tests for understanding the feasibility of the deposited materials as flexible sensor electrodes. In addition, finite element methods (FEM) has been utilized for the LIFT process for effective implementation in process optimization. Finally, energy studies have been made using pre-established theory and FEM results for realizing the major physical phenomena affecting the LIFT process. Considering the potential benefits of the LIFT process, successful fabrication of sensor electrodes may be carried out in future.