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

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.

The primary outputs from the CDT will be cohorts of highly qualified, interdisciplinary postgraduates who are experts in a wide range of sensing activities. They will benefit from a world leading training experience that recognises sensor research as an academic discipline in its own right. The students will be taught in all aspects of Sensor Technologies, ranging from the physical and chemical principles of sensing, to sensor design, data capture and processing, all the way to applications and opportunities for commercialisation, with a strong focus in entrepreneurship, technology translation and responsible leadership. Students will learn in extensive team and cohort engaging activities, and have access to cutting-edge expertise and infrastructure. 90 academics from 15 different departments participate in the programme and more than 40 industrial partners are actively involved in delivering research and business leadership training, offering perspectives for impact and translation and opportunities for internships and secondments. End users associated with the CDT will benefit from the availability of outstanding, highly qualified and motivated PhD students, access to shared infrastructure, and a huge range of academic and industrial contacts.

Immediate beneficiaries of our CDT will be our core industrial consortium partners (MedImmune, Alphasense, Fluidic Analytics, ioLight, NokiaBell, Cambridge Display Technologies, Teraview, Zimmer and Peacock, Panaxium, Silicon Microgravity, etc., see various LoS) who incorporate our cross-leverage funding model into their corporate research strategies. Small companies and start-ups particularly benefit from the flexibility of the partnerships we can offer. We will engage through weekly industry seminars and monthly Sensor Cafés, where SME employees can interact directly with the CDT students and PIs, provide training in topical areas, and, in turn, gain themselves access to CDT infrastructure and training. Ideas can be rapidly tested through industrially focused miniprojects and promising leads developed into funded PhD programmes, for which leveraged funding is available through the CDT.

Government departments and large research initiatives are formally connected to the CDT, including the Department for the Environment, Food and Rural Affairs (DEFRA); the Cambridge Centre for Smart Infrastructure and Construction (CSIC); the Centre for Global Equality (CGE); the National Physics Laboratory (NPL); the British Antarctic Survey (BAS), who all push our CDT to generate impacts that are in the public interest and relevant for a healthy and sustainable future society. With their input, we will tackle projects on assisted living technologies for the ageing population, diagnostics of environmental toxins in the developing world, and sensor technologies that help replace the use of animals in research. Developing countries will benefit through our emphasis on open technologies / open innovation and our exploration of responsible, ethical, and transparent business models. In the UK, our CDT will engage directly with the public sector and national policy makers and regulators (DEFRA, and the National Health Service - NHS) and, with their input, students are trained on impact and technology translation, ethics, and regulatory frameworks.