TOWARD RELIABLE IMPLANTABLE DEVICES: ADDRESSING BIOTIC AND ABIOTIC FAILURE MODES IN MICROSCALE MEDICAL DEVICES
Implantable devices are widely used for a large number of sensing and stimulating applications. However, majority of implantable devices are faced with reliability issues that limit their long-term usability. For example, in implantable glaucoma drainage devices (GDD) that remove excess aqueous humor (AH) from the anterior chamber, the microscale channel of GDDs often gets obstructed due to biofouling and requires additional surgical intervention. Moreover, Platinum (Pt)-based microscale neurostimulation electrodes often corrode during its usage due to irreversible electrochemical reactions, which can diminish their long-term charge-injection performance and damage the surrounding neural substrate. In this work, I will demonstrate methods to mitigate these major challenges of biotic and abiotic nature towards highly reliable and superior implantable transducers. As a proof-of-concept, I will share our latest attempts to develop a smart “self-clearing” GDD by integrating magnetically-powered microactuators inside the drainage tube of GDD to combat biological occlusions. The magnetic microactuators can be controlled using externally applied magnetic fields to mechanically clear biofouling-based obstruction, thereby eliminating the need for additional surgical intervention. I will show that the microactuators are effective in removing proteinaceous film deposited on device surface as well as on the inner surface of the microchannel, which supports our hypothesis that a smart self-clearing GDD may be possible. As a second example, I will demonstrate that a monolayer of graphene can be used to virtually suppress Pt dissolution while maintaining excellent electrochemical functionality. The results of our work to date suggest that graphene can serve as an excellent diffusion barrier that can ameliorate the concerns for Pt dissolution in chronically implanted neurostimulation microelectrodes. In the future, I plan to evaluate the performance of our devices in vivo to demonstrate that our smart self-clearing GDD and graphene-coated Pt microelectrodes can be chronically and reliably implanted while maintaining their superior functional performance.