Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays

Abstract

Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C) has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM). The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA), due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors.

State-of-the-art MEMS and microsystem tools for brain research

“…Substrates can be classified as inorganic (for example, silicon 33 , titanium 107 , diamond 108 , zinc oxide 109 , and silicon carbide 110 ) or organic (for example, carbon fiber 101 , parylene 111,112 , SU-8 105,113 , polyimide 114,115 , and silicone 116 ). Silicone, which includes polydimethylsiloxane (PDMS), is an important class of silicon-based organics that provides a useful range of properties, particularly elasticity, not otherwise available.…”

“…Even more Figure 3 Log scale of elastic modulus for many substrates used in implantable arrays. Seminal research has covered inorganic substrates such as silicon 33 , titanium 107 , diamond 108 , zinc oxide 109 , and silicon carbide 110 . Studies on organic substrates have covered carbon fiber 101 , parylene 111 , SU-8 105,113 , polyimide 114,115 , and silicone 116 .…”

“…Other stiff materials include ultrananocrystalline diamond 108 , SiC 110,133 , and particularly carbon fiber materials 101,134 . These materials are all relatively new to field but have two significant advantages over silicon-a higher fracture toughness and a higher elastic modulus.…”

Micro-texturing into DLC/diamond coated molds and dies via high density oxygen plasma etching

“…For an example, the boron-doped diamond or nano-crystalline diamond coatings are favored for application to electrically conductive substrates and bio-actuators [2,3]. In addition, micro-textures or micropatterns on the metallic or polymer products and tools, work to reduce the friction and wear of their surfaces under the presence of minimum quantity lubrication (MQL) [4,5].…”

Electrochemical Impedance Spectroscopy Studies of HF CVD Diamond Films

“…Diamond lms synthesized by chemical vapor deposition (CVD) have great potential for a variety of applications including microelectronic, optics, electrochemistry and recently also in sensor applications [1]. Such broad range of applications is possible because the diamond lms possess unique properties such as large energy band gap, high carrier mobility, high breakdown voltage, high thermal conductivity, resistance to high temperature and radiation [2].…”