Whisker Alignment in Microparts Using Laser Stereolithography with Applied Electric Field

The purpose of this research is to produce microparts reinforced with unidirectional whiskers using laser stereolithography. Electrically conductive whiskers are added to a liquid photopolymer and an electric field is applied to the liquid photopolymer, which aligns the axes of the whiskers along the direction of the electric field. Then, the photopolymer is solidified with UV laser irradiation in a shape that is adjustable. When the electric field is applied, the whiskers are acted on by the moment that aligns them along the electric field in the liquid photopolymer. The liquid photopolymer does not begin to flow until the shear stress on the surface of the whisker reaches the value of the yield shear stress of the photopolymer. This characteristic is denoted as the Bingham property. Therefore, the whiskers do not rotate until the electric field is lower than the threshold value by means of the Bingham property. The Bingham property is measured and the values of the electric field required to rotate the whiskers are examined both theoretically and experimentally in this paper. Using the above results, solidified polymer structures containing unidirectional whiskers are fabricated.