As of today, local research in neural interfacing has remained limited to the field of neuroscience. This is despite the existence of great potential to embark on more translational research addressing the bioengineering and clinical aspects of neural interfacing (e.g. National Neuroscience Institute and more recently Duke-NUS Graduate Medical School). To realize this objective, we propose to pursue the following specific aims with the participation of co-investigators from the Institute of Microelectronics (IME), National University of Singapore (NUS), and Nanyang Technological University (NTU).

Our research focus in this project involves using cantilever microelectrodes as a neural recording and stimulation interface. A few cantilever microelectrodes in 2-D and 3-D arrangements have been reported. Nevertheless, a fully-integrated cantilever microelectrode array with (1) flexible and bendable cantilevers to reduce damage to axons, (2) microactuation capability to make small adjustments to electrodes sites to re-establish signal quality, and (3) fluid dispensing capability to deliver chemical stimulants as an alternative to electrical charged-based stimulation, has yet to be demonstrated.

With the constantly developing MEMS technology, the multi-function silicon neural probe with the full CMOS-compatibility can be realized. The objective of this research is to develop and successfully fabricate Silicon neural-probes with stable neural-electrode interface for both neuron simulation and signal recording. Use of Silicon for neuroprosthetics addresses the issue of integration on IC chips and many other advantages such as easier fabrication, and smaller size over conventional techniques. In this research, we have taken up a novel design for the implementation of silicon nanowires onto neural probe for localized stress sensing. The Silicon nanowires are incorporated as an integral part of Wheatstone’s network to perform the stress detection and also to minimize the external interference. We have successfully accomplished the device fabrication and we are yet to characterize the structure.

SU-8 is deployed as one of popular materials studied in current polymer probe research trends for their good biocompatibility and mechanical excellence of low Young’s Modulus (less tissue damages) but relatively high stiffness. The high stiffness makes insertion of the probes easier. It helps prevent injury to the tissues due to the large mismatched mechanical properties between silicon materials and tissues, and also eliminates potential risks of mechanical failure of the probe due to large impacts generated during insertion.

In this research, we report an innovative fabrication technique to simplify the process of making SU-8 electrode probes. This new probe provides a narrower gap between electrode and neural cells and such small gap has been reported to be the key for ensuring a good signal acquisition. The bonding quality is characterized by fluidic testing and the stiffness is measured by a mechanical testing. It was seen that fluidic testing verifies not only the bonding quality between the interface of two SU-8 layers, but also the potential application in a chemical stimulation on neural cells, whereas the mechanical testing proves that the fabricated polymer neural electrode probe met the requirement for a successful tissue penetration in a real clinical application.

Selected Publications:

1. Zhuolin Xiang, Hao Wang, Songsong Zhang, Minkyu Je, Wei Mong Tsang, Yong-Ping Xu, Shih-Cheng Yen, Nitish V. Thakor, and Chengkuo Lee, Development of Flexible Neural Probes Using SU-8/Parylene, IEEE NEMS, pp.1076 - 1079, 2013[PDF] [DOI]