Direct Gold Plating Selectively on UV Modified Polymer Film Using Tiopronin-Gold

Abstract

An economic and low toxicity gold plating process for bio-compatible device fabrication was investigated. A tiopronin-gold complex altered by mercaptothiodiazole or mercaptotriazole derivatives gave a form of the complex that could be reduced autocatalytically to enable electroless gold plating. Catalytic ca. 5 nm gold particles were selectively grafted into cycloolefin polymer and polyethylenenaphthalate film surfaces by adsorption of tiopronin-gold complex from solution into 20-30 nm deep ultra-violet light modified surface layers followed by reduction with sodium borohydride. Exposure of the catalyst adsorbed surfaces to baths composed of tiopronin-gold complex, mercaptothiodiazole and ascorbic acid resulted in selective electroless plating on the modified surfaces. Observation of the interface cross-section by transmission electron microscopy revealed that the gold deposits were physically anchored to the substrate by nanometer scale octopus trap like structures. Bio-compatible electronics for in vivo application represent an innovative field of medicine, offering ailment for life quality debilitating health complications. In the applications, sensors and transducers read or relay electronic input or output directly to or from living biological systems, like the brain. In retinal and cochlear neuroprosthesis, neural array implants facilitate direct stimulation of optic nerves with signals from a miniature camera, or direct stimulation of cochlear nerves with signals from a microphone. Research involving conscious neural control to operate external devices like prosthetic robots has also been undertaken. Neural electrode arrays also serve in therapeutic stimulation, bypass or diagnosis of specific neural systems in stroke and head injury patients and in patients suffering from Parkinson's disease, epilepsy, dystonia and severe clinical depression.1-10 Another important application for in vivo electronics is sensors and MEMS on catheters, allowing sensory feedback to the operator or manipulation of a MEMS device internally.11,12 Micro in vivo electronic sensors also offer a means of less invasive direct monitoring by wireless transmission or aid efficient pharmaceutical release. 13Non-toxic, non-allergenic and inert gold and platinum can be used as electrode materials; however toxins and allergens should be avoided in fabrication. Economic plating techniques that rely on bath components and construction materials that are toxic or allergenic introduce health risks and are therefore difficult to implement in fabrication. One approach for deposition of biocompatible gold patterns on poly(dimethylsiloxane) has been described using chemical plating and electrochemical etching. 14 In medicine, tiopronin (TPN) has been used therapeutically as a treatment of cystine disulfide related ailments like cystinuria and prophylaxis of renal cystine calculi, functioning based on an increase in solubility. 15,16 Tiopronin capped gold nanoclusters/nanoparticles (TPN-AuNP) have also been a center of attention in a broad spectrum...

Formation of Micrometer Scale Metal Structures on Glass by Selective Electroless Plating on Photopatterned Titanium and Copper Containing Films

“…Displacement of Cu with Pd also enabled catalytic hypophosphite oxidation, therefore selective electroless Ni and CuNi plating on the TiO 2 –CuPd patterns was similarly achieved. Selective gold deposition was also accomplished by plating in the ascorbate reduced TPN-Au-MTZ electroless Au bath . Electroless Cu, Ni, and Au L-line patterns are displayed in Figure S7.…”

“…150 nm thick film. Gold plating was performed by submersion of a TiO 2 –CuPd pattern that had been submersed in the electroless copper bath for 2 min prior, in a solution of 15 g/L dipotassium phosphate, 2.5 g of nicotinic acid, 2.5 g of 1,2,4-triazole-3-thiol (MTZ), 0.92 g/L tiopronin-gold­(I) complex (TPN-Au), 0.05 g/L PEG1000, and 9.0 g/L ascorbic acid at 70 °C for 30 min to selectively deposit a ca. 200 nm thick gold film.…”

Tailored cell sheet engineering using microstereolithography and electrochemical cell transfer

“…Note that this gold plating has been used to coat surgical tools such as forceps, tweezers, and scissors as commercial products. Detailed procedures for non-cyanide electroless plating were reported in our previous study 24 . Briefly, a cycloolefin polymer flat substrate (2.4 cm × 2.4 cm, Zeon corporation, Japan) was treated with UV light (7.5 mW/cm 2 at 185 nm and 50 mW/cm 2 at 254 nm, KOLI-300S, Koto Electric Co. Ltd., Japan) for 5 min for nanometer-deep etching.…”

Surface modification of PEN and PET substrates by plasma treatment and layer-by-layer assembly of polyelectrolyte multilayer thin films and their application in electroless deposition

“…For example, plasma treatment and ultraviolet (UV) light irradiation are suitable for modifying surfaces because they can raise the surface energy and increase adhesion. [1][2][3][4][5][6][7][8][9][10][11][12] The surface modication by plasma treatment and UV irradiation proceeds via the chemical reactions of the polymers themselves, resulting in the formation of functional groups that govern surface properties. Functional groups can also be introduced by forming thin layers on polymer surfaces.…”