A Paper-Based Oxygen Generation and Sensing Platform

Bioflex - Chronic wound management - Parchment paper - Hydrogen peroxide - Manganese dioxide

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

Flexible/stretchable pH Sensor Array

Bioflex - Chronic wound management

The pH level in a chronic wound bed is a key indicative parameter for assessment of the healing progress. Due to fragility and inability to measure multiple wound regions simultaneously, commercial glass microelectrodes are not well-suited for spatial mapping of the wound pH. To address this issue, we present an inexpensive flexible array of pH sensors fabricated on a polymer-coated commercial paper (palette paper). Each sensor consists of two screen-printed electrodes, an Ag/AgCl reference electrode and a carbon electrode coated with a conductive proton-selective polymeric (polyaniline, PANI) membrane. Laser-machining is used to create a self-aligned passivation layer with access holes that is bonded over the sensing and reference electrodes by lamination technology. Characterization of the pH sensors reveal a linear (r2 = 0.9734) relationship between the output voltage and pH in the 4?0 pH range with an average sensitivity of ?0 mV/pH. The sensors feature a rise and fall time of 12 and 36 s for a pH swing of 8-6-8. The sensor biocompatibility is confirmed with human kertinocyte cells.

Publications

A facile fabrication technique for stretchable interconnects and transducers via laser carbonization

carbonization - pyrolysis - piezoresistance - stretchable - laser

This paper reports a biaxial stretchable interconnect on an elastomeric substrate. To increase the stretchability of interconnects, a 2-D diamond-shaped geometry of gold on a polydimethylsiloxane substrate was adopted in which the potentially breakable points were covered with room temperature liquid alloy. Finite element model simulations were performed to identify the most vulnerable points subjected to stress concentration and optimize the design process. Simulations also indicated an optimum gold thickness and linewidth that result in a minimum stress when the substrate is stretched. Four different geometries were designed, fabricated, and characterized. These included: 1) 2-D diamond-shaped gold lines connected at circular junctions with an intersection angle of 90deg; 2) 2-D diamond-shaped gold lines connected at circular junctions with intersection angles of 120deg and 60deg; 3) 2-D diamond-shaped gold lines separated at circular junctions with an intersection angle of 90deg; and 4) 2-D diamond-shaped gold lines separated at circular junctions with intersection angles of 120 deg and 60deg. A maximum stretchability (DeltaL/L) of ~ 60% was achieved for the design in which the lines and circles were separated and had intersection angles of 120deg and 60deg. A resistance variation of (DeltaR/R) ~ 30% was measured for this configuration.

Publications

Smart Diaper

Autonomous (urine-activated) wireless diaper-embedded UTI (Urinary Tract Infection) monitoring platform

The invented diaper-embedded system is comprised of a flexible urine-activated paper battery, a colorimetric detection unit (LED/strip/photodiode), associated circuitry, wireless transmitter, and metallic traces integrated on a hydrophobic flexible substrate. It provides a fully autonomous (stays dormant before urination) and wireless monitoring of UTI upon the urination, which does not require any operation/intervention from the patient/caregiver. The entire detection and data transmission process completes within 30 minute from the beginning of the urination.

Project website Publications

Paper-based electrochemical power source

Disposable - Water-activated - paper substrate

An inexpensive, rapid and simple method to fabricate flexible zinc-copper electrochemical batteries on a hydrophobic (wax) paper through laser-assisted patterning of metal tapes and salt-impregnated filter papers, with lamination employed for packaging. Experiment results showed that a 3-cell battery lit a green LED (1.70 V) for half an hour and achieved a power density of 0.22 mW/cm2.

Publication