The development of MEMS based biodegradable strain sensors and energy sources for monitoring bone healing

Abstract

A sensor that lasts forever is not always desirable. In recent years, the field of biodegradable electronics has developed to dually address transient disease states and to minimize environmental waste. This presentation focuses on the development of MEMS based biodegradable strain sensors and energy sources for monitoring bone healing. Current demonstrations of biodegradable devices in literature have been limited by materials and fabrication. As such, this research emphasizes the expansion of materials and fabrication schemes for the micropatterning and integration of biodegradable materials in MEMS. The non aqueous electrodeposition of magnesium (Mg), passivation schemes with pulse plated zinc (PP Zn) and fluorinated hydroxyapatite (FHA), barrier encapsulation strategies, as well as degradable conductive composites are examined and, subsequently, harnessed for the development of biodegradable piezoresistive strain sensors and galvanic energy sources. Analogous non degradable strain sensors were developed to provide a basis for comparison, as well as to better understand the intended design space. The results culminated in the in vivo deployment of a wireless strain sensing system within a rodent femoral defect model and cytotoxicity results confirming the biocompatibility of the examined materials. Together, this research demonstrated electroplated Mg based strain sensors and energy sources as a trajectory towards a fully biodegradable system and, beyond the scope of bone healing, supported the field of biodegradable MEMS through the expansion of materials fabrication and characterization for use in widgets not intended to last forever.