(a) Image of the device with syringe and needle inserted. (b) Solid model of the device with all interconnected components: patient-to-chip syringe interface, membrane pump, fluidic resistor, and downstream component. An operator injects the patient sample into the device using the collection syringe directly. The sample is fully contained within the membrane pump, which inflates under the fluid pressure. Subsequently, the pump deflates and pushes the sample downstream, as regulated by the membrane characteristics and the fluidic resistor. (c) Exploded view of the device showing the PMMA and silicone layers. The top PMMA layer is 1.5 mm thick, the silicone layer is 1.6 mm thick, and the bottom PMMA layer is 3.0 mm thick.
Patient-to-chip syringe interface. (a) Magnified view showing the silicone seal, guiding channel for the needle, and check valve. (b) Schematic of the simple check valve enabled by the layered membrane pump design (open under forward pressure and closed under backpressure).
Membrane pump. (a) Magnified view showing stored sample volume. (b) Schematic of the membrane pump inflated under fluid pressure.
Experimental setup used to determine the characteristic time constant of the fluidic RC circuit (shown magnified in the current view).
Pumping capacitance for linear and nonlinear deflections. The capacitance steadily increases when deflection is linear, however, it drops sharply at a transition pressure ( ) as the deflection becomes nonlinear. For different pump radii (3.5 mm (solid), 4.0 mm (dashed), and 4.5 mm (dotted-dashed)) at a fixed membrane thickness of 1.6 mm and elastic modulus of 1600 kPa, the transition pressure decreases with increasing radius. The transition pressures for each pump are indicated in the figure.
Deflection-pressure relationship of the membrane pump for two different membrane thicknesses, 0.5 mm (dashed) and 1.6 mm (solid), at a fixed pump radius of 2.5 mm. For the 0.5 mm thick membrane, linear deflection transitions to nonlinear deflection beyond 0.5 mm, while there is no transition for the 1.6 mm thick membrane. The inset images showthe central portion of the pumps as viewed from the side at 20.7 kPa, 55.2 kPa, and 103.4 kPa for the 0.5 mm thick membrane (left), and at 83.6 kPa and 138.1 kPa for the 1.6 mm thick membrane (right). The dashed lines indicate the base of the spherical cap.
Comparison of pressure and flow rate outputs for DI water and mouse whole blood for different total fluidic resistances. (a) Pressure and (b) flow rate outputs of the membrane pump for DI water for three different fluidic resistors: small (solid), medium (dashed), and large (dotted-dashed) with total resistances of 0.8 kPa min/μl, 1.7 kPa min/μl, and 2.5 kPa min/μl, respectively. The characteristic time constants of the small, medium, and large fluidic circuits were 21 s, 42 s, and 63 s, respectively, with a fixed total capacitance of 0.4 μl/kPa. (c) Pressure and (d) flow rate outputs for mouse whole blood using the same three devices as for DI water. The high viscosity and hematocrit of the whole blood increased the total resistances to 2.2 kPa min/μl, 3.2 kPa min/μl, and 4.0 kPa min/μl, resulting in time constants of 53 s, 74 s, and 97 s for small, medium, and large resistors, respectively. The characteristic time constants were calculated using volume outputs at time intervals of 0.5 min, 1 min, and 2 min (as indicated by arrows) given the volume is the time-integral of the flow rate.
Comparison of pressure and flow rate outputs for DI water and mouse whole blood for different total pumping capacitances. (a) Pressure and (b) flow rate outputs of the membrane pump for a single pump (solid), three pumps in parallel (dashed), and six pumps in parallel (dotted-dashed) with total capacitances of 0.4 μl/kPa, 1.2 μl/kPa, and 2.4 μl/kPa, respectively. The characteristic time constants for the single, three, and six pumps in parallel are 22 s, 62 s, and 121 s, respectively, at a fixed total resistance of 0.8 kPa min/μl. (c) Pressure and (d) flow rate outputs for mouse whole blood using the same three devices as for DI water. The high viscosity and hematocrit of the whole blood increased the total resistance to 2.2 kPa min/μl for the same total capacitances, resulting in time constants of 52 s, 147 s, and 321 s for the single pump, three pumps in parallel, and six pumps in parallel, respectively. The characteristic time constants were calculated using volume outputs at time intervals of 0.5 min, 1 min, and 2 min (as indicated by arrows) given the volume is the time-integral of the flow rate. The pump networks are shown schematically in the figure.
Article metrics loading...
Full text loading...