Development of Parylene-C based Peripheral Mesh Electrode

국문 초록 (Abstract)

기존의 침습형 신경 인터페이스들은 조직과의 물리적인 특성 차이로 인해 신경조직에 광범위한 면역반응을 야기하며 조직은 반흔 조직을 형성한다. 이는 전극의 측정능력 상실로 이어지기 때문에 최근 이러한 면역반응을 줄이는 신경인터페이스가 연구되어지고 있다. 이러한 면역반응을 최소화 할 수 있는 구조가 그물형 구조로 만든 신경인터페이스다. 본 논문은 이 그물형 구조를 통해 장기적으로 말초신경에서 측정이 가능한 Parylene-C 기반 말초신경 인터페이스 개발을 다룬다.

수분 침투율을 낮추기 위해 기존에 사용되는 SU-8이 아닌 Parylene-C를 이용하여 전극을 제작하였다. 또한 뇌와 다른 특징을 가진 말초신경에 최적화하기 위해서, 늘어날 수는 있는 프렉탈 구조를 도입하고 전극의 측정크기 역시 조절하였다. 전극 제작에 필요한 높은 정확도를 가지며 전극의 손상을 최소화하는 Reactive Ion Etching(RIE) 조건을 확립하였다. 또한 RIE 공정을 2번 나눠서 진행하여 금속 RIE 마스크의 micro-sputtering으로 인한 잔여물 문제를 해결하여 그물형 모양의 Parylene-C 전극을 완성하였다.

electrochemical Impedance Spectroscopy를 이용해 전극의 임피던스를 측정한 결과, 전극의 임피던스는 1Khz에서 1.15Mohm이였다. 전극의 in vivo에서 사용 가능성을 알기 위해 Digital Neural Signal Simulator를 이용한 실험에서 모사된 활동전위를 측정하는데 성공하였다. 이어서 진행된 acute animal experiment에서 성공적으로 뉴질랜드 토끼의 좌골신경에서 활동전위를 측정을 하였다.

본 논문은 Parylene-C 기반 말초신경 그물형 전극 개발 및 타당성을 보였다. 앞으로 말초신경에 최소한의 손상을 주며 삽입하는 기술 및 전극 임피던스 등을 개발 및 개선하여 장기적인 말초신경 추적을 하고자 한다.

다국어 초록 (Multilingual Abstract)

Conventional invasive neural interfaces cause a wide range of immune responses to neural tissues due to differences in their physical properties and tissues form scar tissue. Since this leads to a loss of the measuring ability of the electrode, a neural interface that reduces this immune response has recently been studied. The structure that can minimize this immune response is a neural interface made of a mesh structure. This paper deals with the development of a parylene-c based peripheral nerve interface that can be measured in the peripheral nerve in the long term through this mesh structure.

In order to reduce the water penetration rate, electrodes were manufactured using Parylene-C instead of SU-8. In addition, in order to optimize the peripheral nerves with other characteristics of the brain, an stretchable fractal structure was introduced and the measurement size of the electrodes was also adjusted. Reactive Ion Etching (RIE) conditions were established to have high accuracy and minimize damage to electrodes. In addition, the RIE process was divided into two parts to solve the residue problem caused by the micro sputtering of the metal RIE mask, thereby completing a mesh parylene-C electrode. Electrode impedance was measured using electrochemical impedance spectroscopy (EIS). The impedance of the electrode was 1.15 Mohm at 1 kHz. In order to know the potential of electrode use in vivo, I successfully measured the emulated action potential in the experiment using Digital Neural Signal Simulator. Subsequent acute animal experiments were successfully performed to measure activity potential in the sciatic nerve of New Zealand rabbits.

This thesis shows the development and validity of Parylene-C based peripheral neural mesh electrode. In the future, I will develop long term peripheral nerve tracking by developing the insertion technique which have minimal damage to peripheral nerve and improving the electrode impedance

목차 (Table of Contents)

• Abstract ............................................................................................................................................ⅰ
• List of Contents ................................................................................................................................ ⅱ
• List of Tables .................................................................................................................................... ⅲ
• List of Figures ................................................................................................................................... ⅳ
• 1. INTRODUCTION .......................................................................................................................... 1
• 2. METHOD ..................................................................................................................................... 4
• 2.1 Fabrication .............................................................................................................................. 4
• 2.2 Parylene-C based mesh electrode and recording system Assembly ........................................... 7
• 2.3 Electrochemical impedance spectroscopy characterization ...................................................... 7
• 2.4 Digital Neural Signal Simulator test ........................................................................................ 8
• 2.5 strain experiment ................................................................................................................... 9
• 2.6 Surgery and Implantation ........................................................................................................ 9
• 2.7 Recordings .............................................................................................................................. 9
• 3. RESULT ....................................................................................................................................... 10
• 3.1 Fabricated parylene-c mesh electrode ....................................................................................... 10
• 3.2 Electrochemical impedance spectroscopy characterization result ............................................... 11
• 3.3 Digital Neural Signal Simulator test result ................................................................................. 12
• 3.4 Strain experiment result ........................................................................................................... 12
• 3.5 acute in vivo recording ............................................................................................................. 13
• 4. CONCLUSION ............................................................................................................................... 17
• Reference ......................................................................................................................................... 20