Compressive Behaviors of Micropillar Sheets Made of PDMS Material Using the Finite Element Method

Abstract

Thai Microelectronics Center fabricates micropillar sheets from soft lithography techniques and roll-to-roll process which were used as superhydrophobic and superoleophobic surfaces coated on marine structures and medical devices. This research aimed to study appropriate constitutive models and mechanical behaviours of PDMS micropillar sheets with two substrate thicknesses of 1,910 µm and 150 µm under compressive loading using ANSYS Mechanical APDL program. The constitutive models consisted of Mooney-Rivlin (2, 3 and 5 parameters), Ogden (1^st, 2^nd and 3^rd orders), Neo-Hookean, Polynomial (1^st and 2^nd orders), Arruda-Boyce, Gent and Yeoh (1^st, 2^nd and 3^rd orders) models were curved fitting with experiment data from uniaxial compression test. We found that the most accurate constitutive model was Mooney-Rivlin 5 parameter model for the low strain range . The compressive strength and the lateral collapse of micropillars depended on substrate thickness were studied. The lateral collapse of micropillars was found when the substrate thicknesses were 150 µm and 1,910 µm. As the substrate thickness decreased, the compressive strength decreased while the elastic stiffness increased. The maximum compressive forces per one micropillar were 21.060 µN and 18.549 µN for the 1,910 µm and 150 µm thick substrates respectively.