Fig. 3. Backflow elimination, and flow optimization for cell adhesion in different surface treatments.

a Volumetric profile of the flow rate recorded during actuation which shows complete elimination of backflow during actuation. Each peak represents a valve. The high peaks are representative of the pumping valve (middle lifting gate valve) which is double the diameter of the two small gate valves (low peaks). A series of three peaks represent a full actuation cycle b Volume pumped per cycle as a function of actuation time and closing pressure of the microvalve. The valve actuation vacuum was −85 kPa, and the pressure varied from 0 to 45 kPa. For the experiment, an actuation time of 500 ms was selected at 45 kPa closing pressure. c The percentage of cells retained on the device under 45 kPa valve closing pressure and 500 ms actuation time for different PDMS surface treatments. (Ordinary one-way ANOVA; n = 4, **p < 0.05, no significant difference)