In-Situ Formation of Polyethylene Glycol (PEG) Hydrogel Membrane in Microfluidic Fuel Cells

Membranless microfluidic fuel cells operated under two co-laminar flows often face serious fuel cross-over problems, especially when the flow rates are close to zero. In this study, we show that polyethylene glycol (PEG) solutions can be cross-linked in situ in microfluidic channels to form a PEG hydrogel membrane. This membrane prevents mixing of two incompatible electrolyte solutions while allowing diffusion of certain fuel molecules and ions through the membrane. By using PEG monomers of different molecular weight and UV exposure time, the selectivity of the membrane can be tailored with high accuracy. As a proof of principle, we develop a glucose fuel cell with two incompatible electrolytes (acid and base) which do not mix together even at zero flow rate. This glucose fuel cell is able to generate an open circuit voltage up to 400 mV from 5 mM of glucose. This device will be potentially useful for biomedical devices which use glucose as a power source.