A Study on Gallium Coating and Wireless Platform for Implantable Biomedical Applications

Recent research interests in wearable or implantable devices have played a significant role in advancing MEMS technologies into emerging biomedical fields. Novel materials and methods have been extensively explored in creating intrinsically flexible biomedical devices. As a novel nontoxic alternative to mercury, gallium-based liquid metals have been utilized to form functional wearable devices thanks to their unique combination of electrical and fluid properties. However, the adherent tendency of oxidized liquid metals has been a fundamental challenge that needs to be addressed in order to unleash the full potentials. This work reports gallium coating as a simple remedy to convert various microfluidic materials to nonwetting surfaces against gallium-based liquid metals. Quantitative studies on the super-lyophobicity and surface topography are presented to evaluate gallium coated surfaces as nonwetting microfluidic platform for oxidized gallium-based liquid metal droplet manipulation. Implantable functional devices, on the other hand, require wireless operation capability in order to reduce invasiveness to biological bodies while fulfilling monitoring or therapeutic functions. Intramedullary fluid modulation has been reported to enhance bone density and can be employed as a potential treatment to osteoporosis. Aiming at replacing invasive methodology used in these in vivo studies, this work presents an implantable and wirelessly operated intramedullary fluid modulator for on-demand intramedullary fluid modulation. The pressure modulation is evaluated by theoretical model as well as ex vivo and in vivo experiments. Additionally, a wireless pressure sensing system with long range transmission capability is demonstrated as a complement to wireless intramedullary fluid modulator. Details on the system design is discussed, and evaluation results in terms of pressure response and transmission range is presented.