Evaluation of a MEMS-Based Dual Metal-Layer Thin-Film Microelectrode Array for Suprachoroidal Electrical Stimulation

A double metal-layer thin-film platinum microelectrode array was fabricated for implantation between sclera and choroid based on MEMS processing techniques and photosensitive polyimide material. The array was composed of 60 stimulating sites (6 x 10) and four selectable returning electrodes. The diameter of each stimulating electrode was 350 mu m with a center-to-center spacing of 750 mu m. The transient voltage responses of the electrode to current pulse stimulation indicated a charge-injection capacity greater than 52.1 mu C/cm(2) . Acute in vivo animal experiments showed that the implicit time of electrically evoked potentials (EEPs) was 17.09 +/- 1.45 ms at a threshold current of 25.55 +/- 5.43 mu A for a full-row of simultaneously stimulated electrodes (i.e., current applied simultaneously to each of the 10 electrodes). Individual electrode stimulation threshold was 48.57 +/- 6.90 mu A. The corresponding threshold charge densities were 13.28 +/- 2.82 mu C/cm(2) and 25.24 +/- 3.59 mu C/cm(2) , respectively. The spatial spread of the maximally recorded P1 response in the EEPs indicated a correspondence between the retinal stimulation site and the focal response location in the cortex. This method of array fabrication is suitable for acute suprachoroidal stimulation, and has a potential use for the fabrication of a visual prosthesis.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000321737000002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Engineering, BiomedicalRehabilitationSCI(E)EI3ARTICLE4524-5312