A Library of Polymer-based Microelectrode Array Designs for Recording from the Brain of Different Animal Models.

Large-scale network recording technology is critical in linking neural activity to behavior. Stable, long-term recordings collected from behaving animals are the foundation for understanding neural dynamics and the plasticity of neural circuits. Penetrating microelectrode arrays (MEAs) can obtain high-resolution neural activity from different brain regions.

Polymer Implantable Electrode Foundry: A shared resource for manufacturing polymer-based microelectrodes for neural interfaces.

Large scale monitoring of neural activity at the single unit level can be achieved via electrophysiological recording using implanted microelectrodes. While neuroscience researchers have widely employed chronically implanted electrode-based interfaces for this purpose, a commonly encountered limitation is loss of highly resolved signals arising from immunological response over time. Next generation electrode-based interfaces improve longitudinal signal quality using the strategy of stabilizing the device-tissue interface with microelectrode arrays constructed from soft and flexible polymer materials.

Acute in vivo Recording with a Generic Parylene Microelectrode Array Implanted with Dip-coating Method into the Rat Brain.

Flexible polymer-based microelectrode arrays (MEAs) can reduce tissue inflammation and foreign body response and greatly prolong the lifetime of neural implants. However, standard and customized polymer devices are only accessible to limited groups. To better promote the development and application of polymer MEAs, we have launched the Polymer Implantable Electrode (PIE) Foundry and developed a 64-channel Parylene C-based MEA with generic electrodes layout that can be used to record from both cortical and sub-cortical regions in rodents.

A 512-Channel Multi-Layer Polymer-Based Neural Probe Array.

We present for the first time the design, fabrication, and preliminary bench-top characterization of a high-density, polymer-based penetrating microelectrode array, developed for chronic, large-scale recording in the cortices and hippocampi of behaving rats. We present two architectures for these targeted brain regions, both featuring 512 Pt recording electrodes patterned front-and-back on micromachined eight-shank arrays of thin-film Parylene C. These devices represent an order of magnitude improvement in both number and density of recording electrodes compared with prior work on polymer-based microelectrode arrays.

A Parylene Neural Probe Array for Multi-Region Deep Brain Recordings.

A Parylene C polymer neural probe array with 64 electrodes purposefully positioned across 8 individual shanks to anatomically match specific regions of the hippocampus was designed, fabricated, characterized, and implemented for enabling recording in deep brain regions in freely moving rats. Thin film polymer arrays were fabricated using surface micromachining techniques and mechanically braced to prevent buckling during surgical implantation. Importantly, the mechanical bracing technique developed in this work involves a novel biodegradable polymer brace that temporarily reduces shank length and consequently, increases its stiffness during implantation, therefore enabling access to deeper brain regions while preserving a low original cross-sectional area of the shanks.

Application of Parylene-Based Flexible Multi-Electrode Array for Recording From Subcortical Brain Regions From Behaving Rats.

Obtaining multiple single-unit recordings in particular neural networks from behaving animals is crucial for the understanding of cognitive functions of the brain. Attaining stable, chronic recordings from the brain is also the foundation to develop effective cortical prosthetic devices. However, severe immune response caused by micromotion between stiff implants and surrounding brain tissue often limits the lifetime of penetrating, neural recording devices.

Techniques and Considerations in the Microfabrication of Parylene C Microelectromechanical Systems.

Parylene C is a promising material for constructing flexible, biocompatible and corrosion-resistant microelectromechanical systems (MEMS) devices. Historically, Parylene C has been employed as an encapsulation material for medical implants, such as stents and pacemakers, due to its strong barrier properties and biocompatibility. In the past few decades, the adaptation of planar microfabrication processes to thin film Parylene C has encouraged its use as an insulator, structural and substrate material for MEMS and other microelectronic devices.

A review of implantable biosensors for closed-loop glucose control and other drug delivery applications.

Closed-loop drug delivery promises autonomous control of pharmacotherapy through the continuous monitoring of biomarker levels. For decades, researchers have strived for portable closed-loop systems capable of treating ambulatory patients with chronic conditions such as diabetes mellitus. After years of development, the first of these systems have left the laboratory and entered commercial use.

Chronic multi-region recording from the rat hippocampus in vivo with a flexible Parylene-based multi-electrode array.

Neural activities of free-moving animals provide valuable insights into behavior, memory formation and cognitive function of the hippocampus. Unitary activities simultaneously recorded from multiple sub-regions of the hippocampus enable detailed study of hippocampal neural circuits, but require high fidelity recordings with high temporal and spatial resolution. In this work, we explored the possibility of using Parylene-C as the structural material for a penetrating, multi-electrode array designed to record from multiple sub-region of the rat hippocampus.

Acute in vivo testing of a conformal polymer microelectrode array for multi-region hippocampal recordings.

Objective: The success of a cortical prosthetic device relies upon its ability to attain resolvable spikes from many neurons in particular neural networks over long periods of time. Traditionally, lifetimes of neural recordings are greatly limited by the body's immune response against the foreign implant which causes neuronal death and glial scarring. This immune reaction is posited to be exacerbated by micromotion between the implant, which is often rigid, and the surrounding, soft brain tissue, and attenuates the quality of recordings over time.

Passive, wireless transduction of electrochemical impedance across thin-film microfabricated coils using reflected impedance.

A new method of wirelessly transducing electrochemical impedance without integrated circuits or discrete electrical components was developed and characterized. The resonant frequency and impedance magnitude at resonance of a planar inductive coil is affected by the load on a secondary coil terminating in sensing electrodes exposed to solution (reflected impedance), allowing the transduction of the high-frequency electrochemical impedance between the two electrodes. Biocompatible, flexible secondary coils with sensing electrodes made from gold and Parylene C were microfabricated and the reflected impedance in response to phosphate-buffered saline solutions of varying concentrations was characterized.

A flexible parylene probe for in vivo recordings from multiple subregions of the rat hippocampus.

The hippocampus is crucial to the formation of long-term memory and declarative memory. It is divided into three sub-fields the CA1, the CA3 and the DG. To understand the neuronal circuitry within the hippocampus and to study the role of the hippocampus in memory function requires the collection of neural activities from multiple subregions of the hippocampus simultaneously.

Electron-beam lithography for polymer bioMEMS with submicron features.

We present a method for submicron fabrication of flexible, thin-film structures fully encapsulated in biocompatible polymer poly(chloro-p-xylylene) (Parylene C) that improves feature size and resolution by an order of magnitude compared with prior work. We achieved critical dimensions as small as 250 nm by adapting electron beam lithography for use on vapor deposited Parylene-coated substrates and fabricated encapsulated metal structures, including conducting traces, serpentine resistors, and nano-patterned electrodes. Structures were probed electrically and mechanically demonstrating robust performance even under flexion or torsion.

Design of a flexible parylene-based multi-electrode array for multi-region recording from the rat hippocampus.

The hippocampus is a critical deep brain structure in several aspects. It is directly related to the formation of new long-term declarative memory. The malfunction of the hippocampus closely relates to various disease and pathological conditions.

Polymer-coated micro-optofluidic ring resonator detector for a comprehensive two-dimensional gas chromatographic microsystem: μGC ×μGC-μOFRR.

We describe first results from a micro-analytical subsystem that integrates a detector comprising a polymer-coated micro-optofluidic ring resonator (μOFRR) chip with a microfabricated separation module capable of performing thermally modulated comprehensive two-dimensional gas chromatographic separations (μGC ×μGC) of volatile organic compound (VOC) mixtures. The 2 × 2 cm μOFRR chip consists of a hollow, contoured SiO(x) cylinder (250 μm i.d.

Materials for microfabricated implantable devices: a review.

The application of microfabrication to the development of biomedical implants has produced a new generation of miniaturized technology for assisting treatment and research. Microfabricated implantable devices (μID) are an increasingly important tool, and the development of new μIDs is a rapidly growing field that requires new microtechnologies able to safely and accurately function in vivo. Here, we present a review of μID research that examines the critical role of material choice in design and fabrication.

A microfabricated optofluidic ring resonator for sensitive, high-speed detection of volatile organic compounds.

Advances in microanalytical systems for multi-vapor determinations to date have been impeded by limitations associated with the microsensor technologies employed. Here we introduce a microfabricated optofluidic ring resonator (μOFRR) sensor that addresses many of these limitations. The μOFRR combines vapor sensing and fluidic transport functions in a monolithic microstructure comprising a hollow, vertical SiOx cylinder (250 μm i.

Microfabricated optofluidic ring resonator structures.

We describe the fabrication and preliminary optical characterization of rugged, Si-micromachined optofluidic ring resonator (μOFRR) structures consisting of thin-walled SiO(x) cylinders with expanded midsections designed to enhance the three-dimensional confinement of whispering gallery modes (WGMs). These μOFRR structures were grown thermally at wafer scale on the interior of Si molds defined by deep-reactive-ion etching and pre-treated to reduce surface roughness. Devices 85-μm tall with 2-μm thick walls and inner diameters ranging from 50 to 200 μm supported pure-mode WGMs with Q-factors >10(4) near 985 nm.

Microfluidic blood filtration device.

Rapid decentralized biomedical diagnostics have become increasingly necessary in a medical environment of growing costs and mounting demands on healthcare personnel and infrastructure. Such diagnostics require low-cost novel devices that can operate at bedside or in doctor offices using small amounts of sample that can be extracted and processed on the spot. Thus, point-of-care sample preparation is an important component of the necessary diagnostic paradigm shift.