Micropillar array is widely used in bionics, thermodynamics and biomedicine because of its advantages in improving surface tribological properties and enhancing heat transfer [1, 2]. Through-mask electrochemical etching is one of the main methods to fabricate metal micropillar array in large scale [3].

In this study, we studied the etching effect of micropillar array with the method of megasonic assisted through-mask electrochemical etching. An anode vibrating type megasonic source at 1MHz was set up. Micropillar arrays were etched at megasionc intensity of 2W/cm^2. Fig. 1(a) shows the fabrication process of the micropillar array. The mask is prepared by photolithography. During the etching process, anode acts as an acoustic source and radiates megasonic waves simultaneously. Fig. 1(b) shows the micropillar arrays which were etched without megasonic and with megasonic agitation. Uniform micropillars were achieved with megasonic agitation compared to without megasonic agitation. Fig. 1(c) and Fig. 1(d) shows the measured height and diameter of the micropillars. Higher micro columns were obtained with megasonic agitation when the diameters of the micro columns are almost identical. Micropillars with an average diameter of 116.95μm and an average height of 11.31μm were obtained with megasonic agitation. Fig. 1(e) shows the etching factor of the micropillars. Average etching factor of the micropillars etched without megasonic agitation and with megasonic are 2.07 and 2.87, respectively. The method of megasonic assisted through-mask electrochemical etching can achieve much higher etching factor than without megasonic agitation. This work opens new promising fields for development of extensive fabrication methods of micropillar array.

Reference

[1] R. Xiao, R. Enright, E. N. Wang. Langmuir, 26(19) 15070-15075 (2010)

[2] M. Shojaeian, A. Koşar. Exp. Thermal Fluid Sci., 63 45-73 (2015)

[3] T. Baldhoff, V. Nock, A. T. Marshall, J. Electrochem. Soc., 165 (16) E841-E855 (2018)