A flexible, parchment paper/PDMS based platform for local wound oxygenation is fabricated and characterized. The platform consists of a PDMS microfluidic network bonded to a parchment paper substrate. Generation of oxygen occurs by flowing H2O2 through the channels and chemically decomposing it via a catalyst embedded in laser-defined regions of the parchment paper. PDMS is bonded to parchment paper using partially cured PDMS followed by a brief air plasma treatment, resulting in a strong bond. For pressures below 110 Torr the parchment paper is observed to be impermeable to water and hydrogen peroxide. The oxygen permeability of parchment paper is measured to be 1.42 μL/(Torr mm2 min). Using a peroxide flow rate of 250 μL/min, oxygen generation in the catalyst spots raises the oxygen level on the opposite side of the parchment paper from atmospheric levels (21%) to 25.6%, with a long-term (30 h) generation rate of 0.1 μL O2/min/mm2. This rate is comparable to clinically proven levels for adequate healing. Device and material in vitro biocompatibility is confirmed with NIH 3T3 fibroblast cells via alamar blue assays.Publications
Piezoelectric receiver feeds AC signal to a full-wave rectifying circuit to create a constant DC voltage for electrolysis.
The electrolytically-generated gas pressure will be accumulated for pumping the drug out.
Flow rate of 0.1 μL/s with a backpressure of 24.2 Torr.
We present a microorganism-powered thermopneumatic pump that utilizes temperature-dependent slow-kinetics gas (carbon dioxide) generating fermentation of yeast as a pressure source. The pump consists of stacked layers of polydimethylsiloxane (PDMS) and a silicon substrate that form a drug reservoir, and a yeast-solution-filled working chamber. The pump operates by the displacement of a drug due to the generation of gas produced via yeast fermentation carried out at skin temperatures. The robustness of yeast allows for long shelf life under extreme environmental conditions (50 °C, >250 MPa, 5–8% humidity). The generation of carbon dioxide is a linear function of time for a given temperature, thus allowing for a controlled volume displacement. A polymeric prototype (dimensions 15 mm × 15 mm × 10 mm) with a slow flow rate of < 0.23 μL min−1 and maximum backpressure of 5.86 kPa capable of continuously pumping for over two hours is presented and characterized.Publications
We report a method for fabricating inexpensive microfluidic platforms on paper using laser treatment. Any paper with a hydrophobic surface coating (e.g., parchment paper, wax paper, palette paper) can be used for this purpose. We were able to selectively modify the surface structure and property (hydrophobic to hydrophilic) of several such papers using a CO2 laser. We created patterns down to a minimum feature size of 62 ± 1 µm. The modified surface exhibited a highly porous structure which helped to trap/localize chemical and biological aqueous reagents for analysis. The treated surfaces were stable over time and were used to self-assemble arrays of aqueous droplets. Furthermore, we selectively deposited silica microparticles on patterned areas to allow lateral diffusion from one end of a channel to the other. Finally, we demonstrated the applicability of this platform to perform chemical reactions using luminol-based hemoglobin detection.Publications
Our group has developed a variety of micropump devices based on skin contact actuation for controllable transdermal drug delivery. Liquid to vapor phase-change of low boiling point fluorocarbon compounds is employed as the actuation mechanism, requiring no other external power source than the body heat. The induced actuation can result to a gradient of 1000 Pa/oC which is sufficient to drive liquid drug through microneedle arrays. Flowrate performance of 28.8 μL/min and 28.9 kPa backpressure has been illustrated. Single as well as multiple dosage is feasible with the use of unidirectional flap valves. The developed devices exhibit low fabrication costs, employment of biocompatible materials and battery-less operation, making them ideal single- or multiple-use transdermal drug dispensers.Publications