Electrically Induced Decomposition of Thin-Film Nitrocellulose Membranes for On-Demand Biosensor Activation

Implantable or subcutaneous biosensors used for continuous health monitoring have a limited functional lifetime which requires frequent replacement and therefore may be highly discomforting to the patient and become costly. One possible solution to this problem is the use of biosensor arrays where each individual reserve sensor can be activated on-demand when the previous one becomes inoperative due to biofouling or enzyme degradation. Each reserve biosensor in the array is housed in an individiual Polydimethylsiloxane (PDMS) well and is protected from exposure to bodily fluids such a s interstitial fluid (ISF) by a thin-film nitrocellulose me mbrane. Controlled activation is achieved by decomposing over an individual sensor well. Electrically activated decomposition of the nitrocellulose membrane is caused by passing an electric current through a Au/Ti filament placed on top of the membrane. By applyingan energy of 7 mJ to the Au/Ti filament with cross-sectional area of $8\times 10^{7}\mathrm{cm}^{2}$ , a current density of ≈ 10 5 –10 6 A/cm 2 causes explosive decomposition of thin-film Au. Having a thermal decomposition temperature of ≈ 200°C, nitrocellulose is locally heated directly under the Au/Ti filament. This leads to opening of the nitrocellulose membrane allowing for exposure of biosensor to the biofluid.