A pulse-powered microfluidic infusion pump: Preliminary human subject flow rate data

Conventional subcutaneous liquid drug delivery via powered infusion pumps or syringes imposes limitations, including bulkiness, embarrassment, and injection site pain. To address these, we have developed bio-inspired, featherweight, wrist-worn microfluidic infusion pumps that generate a fluid flow driven by the radial pulse. Our objective in this study was to investigate the effect of channel design and user parameters on the device flow rate produced on the wrist, purported to identify subject-specific optimal device designs.

We fabricated two-layer, pulse-driven microfluidic pumps using stereolithographic 3D printing and soft lithography techniques. Devices were tested by affixing them to the wrist above the radial pulse found, and the resulting flow rate was measured using video tracking and the Tracker software. Linear regression models were evaluated to correlate the resulting flow rate and channel design, and user variables. Channel design parameters included channel length, width, inlet depth, and outlet depth. User variables included age, race, sex, height, weight, heart rate, blood pressure, subcutaneous fat percentage, wrist circumference, and the three conditions (at rest, during wrist motion, and after jogging) of the subject.

The study found significant differences in the flow rate of the device between resting and wrist rotation (0.00105 μL/s rest, 0.00513 μL/s wrist rotation, p=0.0003) and between resting and after jogging conditions (0.00172 μL/s after jogging, p=0.0421). No other user or channel design variables demonstrated significant differences in the resting device flow rate. In application, the increased flow rate during physical activity or motion could introduce adverse medicinal responses, suggesting a future need for device design refinement. Channel geometry modification offers a design strategy for flow rate control, and we will explore more channel design combinations to identify optimal device designs tailored for specific subjects.