100x Longevity Improvement of Optoelectronic Implants Through Balancing Integral Electric Fields.

Abstract

Photonics and Optoelectronics are becoming increasingly important for use in implantable devices. In animal trials, although not desirable, failure can lead to the direct replacement of either the component or the test subject. In human implementations, however, the longevity of implantable devices typically needs to exceed 5 years and, in some cases, decades. Traditional hermetic metal packages, per definition, are impervious to water vapour. However, such packaging is unsuitable for structures which are millimetre sized or less. Brain probes encompassing optical micro-emitters must, therefore, use protective passivation/encapsulation layers such as silicon oxynitrides/silicone. However, such protection is prone to electrolytic failure driven by the LED-driving voltages. In this paper, we describe an electrical driving methodology which can improve device lifetime of encapsulated devices by balancing time-averaged electric fields to zero. We have tested the method on commercial optrodes to demonstrate platform independence. We show that, with this method, the time to failure can be increased by over two orders of magnitude.