Figure 1.

Principle and demonstration of vacuum-pressure accelerated movement (V-PAM) in microfluidic chips. (a) V-PAM module composed of a gas-permeable, thin PDMS membrane sandwiched between dead-end microfluidic channels to be filled with biofluid solutions and vacuum channels. A pressure (P) applied at the inlet of microfluidic channels drove liquid into the channel while pushing air trapped at the channel dead end to permeate through the PDMS membrane to the vacuum channel, where a vacuum (V) was maintained to enhance gas permeation through the PDMS membrane. (b) Top view of a microfluidic channel overlaid on top of a vacuum channel with the PDMS membrane sandwiched in between. To prevent deformation of PDMS membranes, an array of rectangular support pillars with a width of W and separated by a distance D was included in the vacuum channel. (c) Bright field images showing filling processes of dye solutions in straight, dead-end microchannels without (top) or with (bottom) V-PAM modules implemented. Images were recorded at different time points after the onset of the filling process (t = 0 s) as indicated. P: 12.5 psi, V: 12.5 psi, W: 100 μm, and D: 50 μm. Vacuum channel length (L) was the same as the length of microfluidic channels, ca. 1 cm. (d) Plot of fluid filling distance as a function of filling time t.