Fluid wetting and penetration characteristics in T-shaped microchannels

Abstract A thorough understanding of media tightness in automotive electronics is crucial for ensuring more reliable and compact product designs, ultimately improving product quality. Concerning the fundamental characteristics of fluid leakage issues, the dynamic wetting and penetration behavior on small scales is of special interest and importance. In this work, four T-shaped microchannels with one inlet and two outlets are experimentally investigated in terms of contact angle dynamics and interface movement over time, generating novel insight into the wetting mechanisms and fluid distribution. With a main channel width of 1 mm, a crevice width of $$w = {0.3}\,\hbox {mm}, {0.4}\,\hbox {mm}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>w</mml:mi> <mml:mo>=</mml:mo> <mml:mrow> <mml:mn>0.3</mml:mn> </mml:mrow> <mml:mspace/> <mml:mtext>mm</mml:mtext> <mml:mo>,</mml:mo> <mml:mrow> <mml:mn>0.4</mml:mn> </mml:mrow> <mml:mspace/> <mml:mtext>mm</mml:mtext> </mml:mrow> </mml:math> and a rounding edge radius of $$r = {0.1}\,\hbox {mm}, {0.2}\,\hbox {mm}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>r</mml:mi> <mml:mo>=</mml:mo> <mml:mrow> <mml:mn>0.1</mml:mn> </mml:mrow> <mml:mspace/> <mml:mtext>mm</mml:mtext> <mml:mo>,</mml:mo> <mml:mrow> <mml:mn>0.2</mml:mn> </mml:mrow> <mml:mspace/> <mml:mtext>mm</mml:mtext> </mml:mrow> </mml:math> , the geometrical effects on the fluid penetration depth in the crevice and the interface edge pinning effect are analyzed quantitatively using an automated image processing procedure. It is found that the measured dynamic contact angles in all parts can be well described by molecular kinetic theory using local contact line velocities, even with local surface effects and abrupt geometry changes. Moreover, a smaller crevice width, a sharper edge and a larger flow velocity tend to enhance the interface pinning effect and prevent fluid penetration into the crevice. The rounding radius has a more significant effect on the interface pinning compared with crevice width. The experimental data and image processing algorithm are made publicly available.