Development of Electroplated Magnesium Microstructures for Biodegradable Devices and Energy Sources

This paper presents fabrication approaches for magnesium (Mg) microstructures embedded in biodegradable polymers using through-mold Mg electrodeposition and metaltransfer-molding. Biodegradable implantable electronics have garnered increasing interest from the medical community for the monitoring and treatment of transient diseases. Magnesium is a biodegradable metal with desirable properties, and the ability to micropattern Mg thick films (i.e., about >1 μm) with direct microelectromechanical systems (MEMS) integration would support the development of more sophisticated and clinically relevant biodegradable devices and microsystems. Magnesium microstructures were electroplated through micropatterned water-soluble molds in a nonaqueous electrolyte and transfer molded into a biodegradable polymer. Electroplated Mg compared favorably with commercial Mg foil based on elemental composition, crystal orientation, electrical resistivity, and corrosion behavior. Magnesium electroplated to a thickness of up to 50 μm showed a grain size of ~10 μm, and minimum feature dimensions of 100 μm in width and spacing. Completely biodegradable Mg and poly-L-lactic acid constructs were demonstrated. The application of Mg thick films toward biodegradable energy sources was explored through the fabrication and testing of biodegradable Mg/Fe batteries. The batteries exhibited a capacity and power of up to 2.85 mAh and 39 μW, respectively. Results confirmed the advantages of electrodeposited Mg microstructures for biodegradable MEMS applications.