Implantable Bioelectronics with Integrated Shape Actuation for Minimally Invasive Neural Interfacing

In this thesis, the integration of fluidic soft robotics with thin-film bioelectronics is explored to create minimally invasive neural interfaces. Electrocorticography is an established neural interfacing technique wherein an array of electrodes enables large-area recording from the cortical surface. Electrocorticography is commonly used for seizure mapping however the implantation of large-area electrocorticography arrays is a highly invasive procedure, requiring a craniotomy larger than the implant area to place the device. In the first section of this work, flexible thin-film electrode arrays are combined with concepts from soft robotics, to realize a large-area electrocorticography device that can change shape via integrated fluidic actuators. We show that the 32-electrode device can be packaged in a compressed state and implanted through a small burr-hole craniotomy then expanded on the surface of the brain for large-area cortical coverage. The implantation, expansion, and recording functionality of the device are confirmed using in-vitro and porcine in-vivo models. The second section of this work outlines two different design tools that can be used during the fabrication of minimally invasive neural implants. The first of these is investigating the use of Silicone and Metal composites to create flexible X-ray opaque markers to enable the imaging of thin film implantable devices that are usually invisible to X-ray imaging. We demonstrate on human cadaveric models that Bismuth and Barium sulfate-mixed silicone markers mixed at 2:1 and 1:1 ratios respectively are visible under X-ray fluoroscopy and that the composites are biocompatible. Therefore, this work provides a tool that enables imaging of thin-film bioelectronics within the body. The second of these tools is the creation of ultra-thin Parylene C fluidic chambers to enable actuation within thin-film implants. We show that through the optimisation of the laser power parameters of a CO2 laser cutter, bonding between two 4 µm Parylene C layers can be achieved, forming a fluidic chamber capable of withstanding fluidic pressures >70 kPa, higher than previously reported. The ultra-thin fluidic chambers were integrated with thin-film bioelectronic arrays to form three different styles of peripheral nerve interfaces, which were validated in vivo on the sciatic nerve of an acute rodent model. The work in the creation of a minimally invasive Electrocorticography device, combined with the thin-film fabrication tools outlined, shows that the integration of shape actuation into neural implants provides a clinically viable pathway to realize large-area neural interfaces via minimally invasive surgical techniques.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2024

Author dc:creator

• Coles, Lawrence

Advisor dc:contributor.advisor

• Malliaras, George

• Bioelectronics
• Neural Interfaces

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/3a493c3f-3e85-4703-aeaf-d9bd1252b885/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

Author Identifier

0000-0002-4288-9691

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/382918