Electrical neural recordings are based on the measurement of voltage differences by an electrode located in the proximity of neurons. Micro-electrodes are used to record single cell action potentials, while macro-electrodes record local field potentials, an overlay of the electrical activity of thousands of neurons. Electrocorticography (ECoG) employs an array of macro electrodes to record the electrical activity from the cortical surface of the cerebral cortex. It has the advantage of being less invasive and having a larger area coverage than micro electrodes, as well as having a higher spatial resolution than electroencephalography. However, commercial ECoG arrays are based on passive technologies, having a limited electrode count and low spatial resolution, which heavily under-samples cortical areas. A significant gap exists in available neuro technologies, as is not possible to record neural activity in humans at the mesoscopic scale of resolution, between microelectrodes and current ECoG arrays; new technologies are needed that allow measuring with high spatiotemporal resolution and with a large area coverage. Microfabrication technologies provide a way to increase the spatial resolution and electrode count of ECoG arrays. Recent reports of fabricated μECoG arrays have shown that novel neuro technologies are a key enabler in neuroscience research, as they have allowed to refute the hold idea that it was not possible to detect action potentials from the surface of the human cortex. However, among the main limitations in scaling the number of channels are the increase of the number of interconnects, as well as the increase of the size of the external connector to the readout electronics. The incorporation of active electronics into electrode arrays can overcome these limitations. The use of transistors allows switching and therefore multiplexing, enabling the reduction of signal lines but with an increase on the number of recording sites, an indispensable step for a miniaturized and convenient connection to an external system. Additionally, due to the soft, curvilinear surface of the brain, conformal electrodes are desirable in order to minimize unwanted tissue interference and to maximize the recorded signal amplitudes. Soft neural interfaces made from thin and flexible materials offer improved biological integration and long-term stability of the measurement, as they minimize the mechanical mismatch between neural tissue and the implantable device. Progress in spatial resolution and compactness of flexible neural probes relies on the integration of thin-film transistors (TFTs). Amorphous metal oxide semiconductors TFTs present themselves as an excellent building block for these devices, due to their good electrical characteristics, such as high electron mobility and good large area uniformity, the fact that they can be fabricated on flexible polymeric substrates, and their stablished use as switching elements in large area electronics. The development of a large-scale, high-density, flexible neural probe will help to bridge the gap in existing neuro technologies by offering high spatial resolution and spatial sampling coverage of the brain tissue. This device has tremendous clinical and research potential, as it would allow to study network-level organization of neural circuits in cortical columns, could provide a better tool for mapping the epileptic foci during surgical intervention in cases of drug resistant epilepsy, or could be used as a novel brain-machine interface.
The object of this PhD is to design and develop this device based on the large-area electronics platform available in imec, to verify its in-vitro bio-compatibility and the subsequent testing in appropriate in-vivo environments.
Required background: Engineering Science, Engineering Technology or equivalent, additional medical background is an asset
Type of work: 10% literature, 10% design, 40% technology exploration, 40% (medical) characterisation
Supervisor: Sebastian Haesler
Daily advisor: Cedric Rolin
The reference code for this position is 2020-085. Mention this reference code on your application form.
Chinese nationals who wish to apply for the CSC scholarship, should use the following code when applying for this topic: CSC2020-44.