Micro-stereolithography photopolymer solidification patterns for various laser beam exposure conditions

Micro-stereolithography is a novel micro-manufacturing process that fabricates 3D microstructures by solidifying the photopolymer using a UV laser in a layer-by-layer fashion. In this paper, variation in the photopolymer solidification pattern due to the scanning pattern and pitch of a focused laser beam was investigated experimentally. Also, experiments were conducted to determine the effects of the layer thickness on the solidification width and depth in multi-layer solidification. The experimental results were compared to numerical simulations. The results showed that a zigzag-shaped scanning pattern was faster and more stable than a crank-shaped pattern. It was also determined that the scanning pitch should be selected according to solidification depth and width for a given scanning pattern, and that the layer thickness has little effect on the solidification depth. Based on the results, several microstructures were successfully fabricated, such as a micro-tube with a helical separation wall and a microlink.Nomenclature P_L The power of the laser beam - The wavelength of the laser beam - f The focal length of the focusing lens - z The depth from the surface of photopolymer - V_S The scanning feed of the laser beam - W₀(z) The Gaussian half-width of the focused laser beam at a given depth z - E_C The critical exposure of the photopolymer - D_P The penetration depth of the photopolymer - W_{0 min} The Gaussian half-width at the focal point - R The Gaussian half-width of the laser beam that passes into the focusing lens - w The scanning width of the laser beam - L The solidified width of the photopolymer - h The solidified depth of the photopolymer - D₁ The layer thickness - D₂ The total solidified depth in a multi-layer solidification