Development of minimally invasive, flexible implants for closed-loop cortical sensing and stimulation

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

Electrocorticography (ECoG) is a neural implanted interface consisting of an array of electrodes acting as sensors to record brain functionality. This type of neural-implant, placed either epi- or subdurally on the cortical surface, allows for both high spatial and temporal resolution of neural measurements and allows for large areas of the brain to be mapped. The integrated electrodes in the ECoG array measure the averaged local electrical field potentials produced by the neurons in the cerebral cortex through direct contact with the cortical surface. ECoG sensing arrays are currently in clinical use a diagnostic tool in surgical epilepsy treatment, guiding surgical intervention.

Previous studies aimed at ECoG sensing array development have focused on the use of flexible, biocompatible materials as the substrate, as flexible ECoG array designs also for better contour matching to the cortical surface, improving the signal to noise ratio of the measurements. However, whilst there has been exploration of flexible ECoG designs, ECoG sensing and stimulating technologies are still very invasive, requiring a craniotomy to be performed on an area larger than the implanted ECoG array. This procedure is high risk due to increased risk of infection during the procedure, therefore by using flexible bioelectronics with shape-adaptive material design, an ECoG electrode array could be designed that could be implanted through less invasive surgical methods, such as a keyhole craniotomy. By reducing the invasiveness of flexible ECoG sensors, it allows for the reduction of both surgical risk and cost, increasing the availability of these sensors for clinical applications.

Therefore, our project's aim is to design flexible ECoG neural implants that can be implanted with minimally invasive surgical technique through the combination of bio-compatible materials and microfluidic design, whilst still retaining the high accuracy and spatial resolution of existing ECoG technologies. We aim to produce an ECoG array that can be rolled using microfluidics to reduce the invasiveness of implantation. Using a rolled device which can be expanded using microfluidics, the size of the craniotomy required can be reduced, reducing the risk of implantation.

To achieve these project aims, we will be evaluating suitable bio-compatible and flexible materials for the ECoG platform. The materials will be assessed for their long-term stability in in-vivo conditions, and their ability to integrate a microfluidics design into the substrate. With a suitable material chosen, we will investigate microfluidic system designs that can create a flexible ECoG platform with a suitable coverage of the cortical surface that can be unrolled using microfluidics. The performance of the platform's ease of implantation and removal will be evaluated initially using simulated cortical surfaces. After integrating electrodes into the flexible platform, the electrode impedance and leakage current will be evaluated using Electrochemical Impedance Spectroscopy through accelerated aging stability tests.

By developing minimally-invasive ECoG arrays for medical diagnosis and treatment, this PhD aligns with the EPSRC's research areas of Sensors and Instrumentation, and Clinical Technologies.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S023046/1 01/10/2019 31/03/2028
2259381 Studentship EP/S023046/1 01/10/2019 30/09/2023 Lawrence Christopher Coles