Parylene flexible neural probes integrated with microfluidic channels

Abstract

The fluidic channel in the flexible probe has three functions: (i) to inject chemicals into the tissues, (ii) to measure the neural activities from the tissues, and (iii) to improve the mechanical stiffness of the probe by filling the channel with a solid material. A 10-microm-thick microfluidic channel was embedded into the probe by using sacrificial photoresist patterns. Polyethylene glycol (PEG), which is solid at room temperature and dissolves when in contact with water, was used to fill the channel and increase the stiffness of the probe before insertion into the tissue. The impedance of the electrode inside the fluidic channel was around 100 kOmega at 1 kHz when the channel was filled with saline solution. We were able to insert the probe into a rat's brain and measure the neural signals with the electrode.

Effect of Thermal and Deposition Processes on Surface Morphology, Crystallinity, and Adhesion of Parylene-C

“…Parylene films with different functional groups have been extensively studied as encapsulation materials for biomedical or microelectronic applications; examples include stents, pacemakers, microelectronics, capacitive sensors, and solder joints. (1)(2)(3)(4)(5)(6)(7) Among the Parylene variants, Parylene-N and -C are currently approved by the Food and Drug Administration (FDA) as class VI polymers, allowing them to be used in biomedical devices. (8) A fully integrated, wireless neural interface device is being developed to restore functions to patients with neurological disorders, (9) and Parylene-C was studied as a conformal, hermetic, and biocompatible encapsulation layer for the device.…”

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.…”

Controlled delivery for neuro-bionic devices

“…The first involves drug-eluting structures formulated with anti-inflammatory drugs [21,22,23,24,25] and neurotrophin-eluting hydrogels [26,27,28,29,30,31]. The second approach involves integration of microfluidic channels into neural prostheses for in situ delivery of bioactive molecules with high temporal and spatial resolution [32,33,34,35,36,37,38,39]. Finally the use of organic conductive polymer (OCP) coatings, a novel class of materials that significantly decrease the impedance of electrodes, and also can provide controlled delivery of bioactive molecules at the electrode-neural interface [40,41,42,43,44,45,46,47,48,49,50].…”

“…Microfluidic channels have also been built into parylene flexible neural recording probes [34]. Compared to rigid silicon probes, these flexible neural probes are of increasing interest as they conform to the shape and deformation of soft tissue.…”