In vitro and in vivo evaluation of ultrananocrystalline diamond for coating of implantable retinal microchips

Abstract

In this work, ultrananocrystalline diamond (UNCD) thin films were evaluated for use as hermetic and bioinert coatings for a retinal microchip. These films were deposited on highly conductive Si substrates at different temperatures (from 400 to 800 degrees C), using microwave plasma enhanced chemical vapor deposition with argon-rich Ar/CH4 gas mixtures and different relative amounts of hydrogen (0-20%). Scanning electron microscopy studies showed that all the films are dense and continuous. Results of cyclic voltammetry test revealed that when there was <2% of hydrogen in the plasma, the film obtained renders the surface electrochemically inactive, with very low leakage currents ( approximately 4 x 10(-7) A/cm2 at +/-5 V). In addition, in vivo tests of the UNCD-coated Si samples were performed by implanting them in the eyes of rabbits for 4-6 months within the eye physiological environment. According to all these results, it was concluded that UNCD is a promising candidate for use as the encapsulating coatings for implantable retinal microelectronic devices.

Improvement on the synthesis technique of ultrananocrystalline diamond films by using microwave plasma jet chemical vapor deposition

“…The UNCD films contain excellent electron field emission [1,2], tribology [3], far smoother surface [4], and unique ability to incorporate n-type dopants [5] could be potentially used for fabrication of multifunctional devices and with attracted great research attention [6][7][8][9]. In the syntheses of UNCD films, microwave plasma chemical vapor deposition (MPCVD) using Ar-rich/CH 4 growth chemistry was frequently used for achieving the enhancement of species activity and diamond secondary nucleation to form nano-sized grains [10][11][12][13].…”

Cytotoxicity evaluation of nanocrystalline diamond coatings by fibroblast cell cultures

“…Thus, a wide range of applications is anticipated for NCD, particularly in the biomedical field. Implants and surgical instruments for dentistry, cardiology, orthopedics, ophthalmology, arterial and venous disorder repair, as well as biosensors and scaffolds for tissue engineering, are just some examples where the use of NCD is particularly innovative [2][3][4][5][6][7][8][9]. In addition, NCD films exhibit the highest resistance to bacterial colonization when compared to medical steel and titanium [10], a relevant issue since bacterial infection associated with the use of biomaterials is still a significant clinical problem.…”

Synthesis and characterization of smooth ultrananocrystalline diamond films via low pressure bias-enhanced nucleation and growth

“…Ultrananocrystalline diamond ͑UNCD͒ films developed at Argonne National Laboratory 1 are outstanding material candidates for the fabrication of multifunctional devices, such as for microelectromechanical/nanoelectromechanical systems ͑MEMS/NEMS͒, 2,3 requiring high Young's modulus, low friction coefficient, and high resistance to wear, requiring low threshold voltage for electron emission, 4 and biomedical devices, 5 requiring bioinertness and/or biocompatibility. Improving the performance of UNCD films for MEMS/NEMS devices requires either the optimization of the synthesis process using the original Ar-rich growth chemistry developed to synthesize UNCD films, or developing new processes that yield stress-free UNCD films with stronger adhesion to the substrate, higher growth rate, and smoother surfaces.…”