Fig. 4

The functions of the inlet port. a The inflow of biomolecules cultured at the bottom of the gradient chip inlet. The unintended cell culture area of (i) the inlet port of the improved gradient chip and (ii) the reservoir without the port. Mass fraction contours of biomolecules under flow rate conditions of (iii and iv) 0.342 μL/h and (v and vi) 3.42 μL/h. b Mass fraction graphs measured at the center of the microfluidic channel (red colored point) under flow rates of (i) 0.342 μL/h and (ii) 3.42 μL/h. The red points in the inset images indicate where the mass fractions of the biomolecules were measured. c As a passive valve to prevent flow between the inlets during chip handling: schematics of (i) the capillary force on the inlet port fluid and (ii) the hydrostatic force generated by the height difference between the inlet ports of the inclined gradient chip. d A graph of the forces applied to the fluid in the gradient chip inlets