Rapid manufacture of modifiable 2.5-dimensional (2.5D) microstructures for capillary force-driven fluidic velocity control

Abstract

A cost-effective, straightforward and modifiable 2.5D microfabrication methodology, as we term multi-layer-tape lithography, is presented here for the first time. It uses a commercial scalpel to prototype 2.5D multilevel microchannels on commercial tape as thin as 500 μm in minutes. Three functional microfluidic devices are applied with this methodology, and display high performance regarding microdroplet formation, multiphase flux and self-powered sequential fluid delivery. We find the microchannel height of a 2.5D microchip can efficiently control capillary force-driven flow velocity. The autonomous sample flow rates through 55 mm long microchannels are 0.1 μL s⁻¹, 0.21 μL s⁻¹ and 0.39 μL s⁻¹ when multilevel microchannel heights are 200 μm, 300 μm, and 400 μm, respectively. After detachment of two, one, and one layers of tape from the three microchannels of a 2.5D tape-master, the microchannel heights are modified to 100 μm, 250 μm and 300 μm, with the autonomous sample flow rate changing to 0.03 μL s⁻¹, 0.15 μL s⁻¹ and 0.28 μL s⁻¹, correspondingly. In contrast with 2D microfabrication technology, we anticipate that multi-layer tape lithography will pave the way for researchers, especially those from resource-limited labs, to develop cost-effective, practical, self-powered, and disposable 2.5D microfluidic devices.