Underpass fabrication between Si-based straight-line and arc-shaped open microchannels

Si-based double-layer underpass open microchannels have been designed and fabricated for microfluidic applications in the field of microelectromechanical systems. The top channel has been carefully designed into S-shaped, spiral, and F-shaped configurations along the ⟨100⟩ crystal direction to facilitate fluid steering, velocity modulation, splitting, and fusion. Meanwhile, the bottom channel has been prepared along the ⟨110⟩ direction, enabling it to be semi-buried into the top channel at a 45-deg angle. A 25% tetramethylammonium hydroxide solution has been utilized to create a distinctive overlapping microchannel structure by removing material from the overlapping part of the two layers of channels. This resulted in intersecting microchannels that are not connected, exhibiting significant structural advantages over traditional single-layer microchannels. With this innovative design, two distinct liquids can be delivered independently and efficiently in the same area.