TY - JOUR
T1 - Nonhermetic encapsulation materials for mems-based movable microelectrodes for long-term implantation in the brain
AU - Jackson, Nathan
AU - Anand, Sindhu
AU - Okandan, Murat
AU - Muthuswamy, Jitendran
N1 - Funding Information:
Manuscript received December 10, 2008; revised May 8, 2009. First published October 6, 2009; current version published December 1, 2009. This work was supported by National Institutes of Health Grant R01NS055312. Subject Editor A. J. Ricco.
PY - 2009/12
Y1 - 2009/12
N2 - In this paper, we have fabricated and tested several composite materials with a mesh matrix, which are used as encapsulation materials for a novel implantable movable-microelectrode microelectromechanical-system (MEMS) device. Since movable microelectrodes extend off the edge of the MEMS chip and penetrate the brain, a hermetically sealed encapsulation was not feasible. An encapsulation material is needed to prevent cerebral-spinal-fluid entry that could cause failure of the MEMS device and, at the same time, allow for penetration by the microelectrodes. Testing of potential encapsulation materials included penetration-force measurements, gross-leak testing, maximum-pressure testing, and biocompatibility testing. Penetration-force tests showed that untreated mesh matrices and silicone-gel-mesh composites required the least amount of force to penetrate for both nylon 6,6 and polypropylene meshes. The silicone-gel-, poly(dimethylsiloxane)-, polyimide-, and fluoroacrylate-mesh composites with the nylon-mesh matrix were all able to withstand pressures above the normal intracranial pressures. Fourier-transform infrared-spectroscopy analysis and visual inspection of the implanted devices encapsulated by the silicone-gel-mesh composite showed that there was no fluid or debris entry at two and four weeks postimplantation. We conclude that a composite of nylon and silicone-gel meshes will meet the needs of the new generation of implantable devices that require nonhermetic encapsulation.
AB - In this paper, we have fabricated and tested several composite materials with a mesh matrix, which are used as encapsulation materials for a novel implantable movable-microelectrode microelectromechanical-system (MEMS) device. Since movable microelectrodes extend off the edge of the MEMS chip and penetrate the brain, a hermetically sealed encapsulation was not feasible. An encapsulation material is needed to prevent cerebral-spinal-fluid entry that could cause failure of the MEMS device and, at the same time, allow for penetration by the microelectrodes. Testing of potential encapsulation materials included penetration-force measurements, gross-leak testing, maximum-pressure testing, and biocompatibility testing. Penetration-force tests showed that untreated mesh matrices and silicone-gel-mesh composites required the least amount of force to penetrate for both nylon 6,6 and polypropylene meshes. The silicone-gel-, poly(dimethylsiloxane)-, polyimide-, and fluoroacrylate-mesh composites with the nylon-mesh matrix were all able to withstand pressures above the normal intracranial pressures. Fourier-transform infrared-spectroscopy analysis and visual inspection of the implanted devices encapsulated by the silicone-gel-mesh composite showed that there was no fluid or debris entry at two and four weeks postimplantation. We conclude that a composite of nylon and silicone-gel meshes will meet the needs of the new generation of implantable devices that require nonhermetic encapsulation.
KW - Bio-microelectromechanical systems (MEMS)
KW - Composite
KW - Neural implant
KW - Neural prostheses
KW - Packaging
KW - Reliability
UR - http://www.scopus.com/inward/record.url?scp=71549129569&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=71549129569&partnerID=8YFLogxK
U2 - 10.1109/JMEMS.2009.2030075
DO - 10.1109/JMEMS.2009.2030075
M3 - Article
AN - SCOPUS:71549129569
SN - 1057-7157
VL - 18
SP - 1234
EP - 1245
JO - Journal of Microelectromechanical Systems
JF - Journal of Microelectromechanical Systems
IS - 6
M1 - 5280304
ER -