Electrolysis-based Parylene Balloon Actuators for Movable Neural Probes

In order to track a specific neuron and keep good sampling neural signals during chronic implantation, the neural probes are highly desired to have moving capability. This paper presents a novel electrolysis-based parylene balloon actuator fabricated with MEMS technology. The actuator is integrated with silicon probe to make it movable. A new fabrication technology has been developed to build a parylene balloon structure with silicon spring structure, electrolysis electrodes and electrolyte inside. By applying little current to electrolysis electrodes, high pressure is generated inside the parylene balloon by electrolysis. The spring structure is stretched with the parylene balloon expansion. Therefore the neural probe is moved by the actuation. The electrolysis actuator can generate large stain and pressure, requires modest electrical power and produces minimal heat. Due to the large volume expansion obtained via electrolysis, the small actuator can create a large force. The new electrolysis actuators for movable neural probes have been fabricated and validated

Ion liquid chromatography on-a-chip with beads-packed parylene column

A parylene-MEMS ion-exchange Liquid Chromatography (LC) chip is presented here. The chip is integrated with microfluidic I/O ports, a separation column, frits/filters, and a conductivity detector. The column is packed with conventional LC stationary phase support materials, i.e. micro-beads with surface functional groups. To withstand high pressure normally encountered in high performance liquid chromatography (HPLC), a self-aligned, channel-anchoring technique is developed to increase the pressure rating of the parylene microfluidic devices from 30 to at least 800psi. On-chip injection, separation and detection of anions in water, with ~25 ppm concentration, have been successfully demonstrated. To our knowledge, this is the first demonstration of microbeads-packed column ion liquid Chromatography (LC) on a chip

Parylene coated silicon probes for neural prosthesis

Silicon neural prosthetic probes require reliable sensing electrodes able to access deep cortical structures without breakage. However, manufacturing limitations have prevented a strong and biocompatible silicon electrode array from reaching this goal. We here demonstrate the first high-density, parylene-coated silicon probe (1.2 cm long) with micro-fabricated electrodes that is able to be inserted in vivo without failure. This work also presents new experimental results for array shank deflection testing, lifetime soak testing as well as the in vitro electrical characterization of the gold and platinum micro-electrodes. These results allow us to optimize the geometry and treatment for both the silicon probe and the metal electrodes

Monolithic Silicon Probes with Flexible Parylene Cables for Neural Prostheses

This work presents the first parylene-insulated silicon probes, which are used for neural prostheses to record high-level cognitive neural signals. With parylene technology, our probes have several advantages compared with the current devices. First, instead of inorganic materials (e.g. silicon dioxide, silicon nitride), the electrodes and conduction traces on the probes are insulated by parylene, an easily-deposited polymer with mechanical flexibility and biocompatibility. As a result, the probes exhibit better electrical and mechanical properties. Second, flexible parylene cables are monolithically integrated with the probes, which arm the probes with very high flexibility to be easily assembled to a high density 3-D array and at the same time provide an ideal method to transmit neural signals through skull during chronic recording. The all dry fabrication process and a 4 X 4 probe array (64 electrodes) were demonstrated. The probes were successfully tested electrically and mechanically in rat cortex. Neural signals were properly recorded

A New Multi-Site Probe Array with Monolithically Integrated Parylene Flexible Cable for Neural Prostheses

This work presents a new multi-site probe array applied with parylene technology, used for neural prostheses to record high-level cognitive neural signals. Instead of inorganic materials (e.g. silicon dioxide, silicon nitride), the electrodes and conduction traces on probes are insulated by parylene, which is a polymer material with high electrical resistivity, mechanical flexibility, biocompatibility and easy deposition process. As a result, the probes exhibit better electrical and mechanical properties. The all dry process is demonstrated to fabricate these probe arrays with monolithically integrated parylene flexible cables using double-side-polished (DSP) wafers. With the parylene flexible cables, the probes can be easily assembled to a high density 3-D array for chronic implantation

Parylene coated silicon probes for neural prosthesis

Silicon neural prosthetic probes require reliable sensing electrodes able to access deep cortical structures without breakage. However, manufacturing limitations have prevented a strong and biocompatible silicon electrode array from reaching this goal. We here demonstrate the first high-density, parylene-coated silicon probe (1.2 cm long) with micro-fabricated electrodes that is able to be inserted in vivo without failure. This work also presents new experimental results for array shank deflection testing, lifetime soak testing as well as the in vitro electrical characterization of the gold and platinum micro-electrodes. These results allow us to optimize the geometry and treatment for both the silicon probe and the metal electrodes

Parylene coated silicon probes for neural prosthesis

Silicon neural prosthetic probes require reliable sensing electrodes able to access deep cortical structures without breakage. However, manufacturing limitations have prevented a strong and biocompatible silicon electrode array from reaching this goal. We here demonstrate the first high-density, parylene-coated silicon probe (1.2 cm long) with micro-fabricated electrodes that is able to be inserted in vivo without failure. This work also presents new experimental results for array shank deflection testing, lifetime soak testing as well as the in vitro electrical characterization of the gold and platinum micro-electrodes. These results allow us to optimize the geometry and treatment for both the silicon probe and the metal electrodes

Parylene Technology for Neural Probes Applications

Neural probes are important tools in detecting and studying neuron activities. Although people have been working on neural probe development for a long time, the current neural probes (including metal-wire probes and silicon neural probes) are still far from being satisfactory. An ideal neural probe array should have good biocompatibility, high-density electrodes with high signal-to-noise ratio, flexible cables for interconnections, integrated electronics, and even integrated actuators to track neuron movement. The work of this thesis focused on applying parylene technology to neural probes development to make a new generation of neural probes with better functions. With the properties of high electrical resistivity, mechanical flexibility, biocompatibility, low coefficient of friction, and an easy deposition/etching process, parylene is a good material for neural probe applications. In this thesis, we have designed, fabricated, and characterized a new parylene neural probe with a long, flexible parylene cable for a neural prosthesis system. Parylene layers are first used on the silicon probe shank with multiple electrodes as insulation and protective layers. And long parylene flexible cables are first monolithically integrated with silicon neural probes. A 96-electrode high-density, 3-D neural probe array for chronic implantation has been demonstrated. Different types of electrolysis actuators (including a silicon diaphragm actuator and a parylene balloon actuator) have been made and tested. The research on electrolysis-based actuators shows their great potential to be used for movable neural probes. Compared with the traditional silicon neural probes (e.g., the Michigan probes, the Utah electrode arrays), our microfabricated neural probes have much longer and stronger probe shanks (8 or 12 mm long, able to penetrate the human pia) and much longer flexible parylene cable (about 7 or 12 cm, long enough to go through a percutaneous connector and the human skull). At the same time, our new probe arrays are shown to have better biocompatibility (being totally covered with parylene material), lower stress, better penetration ability, and greater flexibility for making high-density 3-D arrays and for use in chronic neural signal recording implantation.</p

On-Chip Chromatography-Based Chemical Sensing

We are developing a highly sensitive and selective on-chip chromatography-based chemical sensing system, which has the capability to detect most common ions, such as nitrite, nitrate, fluoride, chloride, phosphate and sulphate, in drinking and underground water, with the sensitivity of PPM to PPB level, and within a few minutes or even fractions of a second. The proposed system consists of two major parts: on-chip chromatography system and chemical sensing system. The integrated chromatography system is built with parylene microfluidic technology. Two sensing techniques, one based on conductivity, the other on surface plasmon resonance (SPR), are being explored for their exceptional sensitivity and miniaturization capability