Flexible, multifunctional neural probe with liquid metal enabled, ultra-large tunable stiffness for deep-brain chemical sensing and agent delivery (original) (raw)
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Frontiers in Neuroscience, 2021
Flexible polymer neural probes are an attractive emerging approach for invasive brain recordings, given that they can minimize the risks of brain damage or glial scaring. However, densely packed electrode sites, which can facilitate neuronal data analysis, are not widely available in flexible probes. Here, we present a new flexible polyimide neural probe, based on standard and low-cost lithography processes, which has 32 closely spaced 10 μm diameter gold electrode sites at two different depths from the probe surface arranged in a matrix, with inter-site distances of only 5 μm. The double-layer design and fabrication approach implemented also provides additional stiffening just sufficient to prevent probe buckling during brain insertion. This approach avoids typical laborious augmentation strategies used to increase flexible probes’ mechanical rigidity while allowing a small brain insertion footprint. Chemical composition analysis and metrology of structural, mechanical, and electri...
2020
Flexible probes for brain activity recordings are an attractive emerging approach that reduces mechanical mismatch between probe and neuronal tissue, thus minimizing the risk of brain damage or glial scaring. Although promising, flexible probes still present some technical challenges namely: i) how to overcome probe buckling during brain insertion given its intrinsically low mechanical rigidity; ii) how to fabricate closely spaced electrode configurations for high density recordings by standard lithography techniques in the flexible substrate. Here, we present a new flexible probe based solely on standard and low-cost lithography processes, which has closely spaced 10 μm diameter gold electrode sites on a polyimide substrate with inter-site distances of only 5 μm. By using a double-layer design and fabrication approach we were able to accommodate closely spaced electrode sites at two different depths from probe surface while also providing additional stiffening, just sufficient to p...
Targeted delivery of neurochemicals and biomolecules for neuromodulation of brain activity is a powerful technique that, in addition to electrical recording and stimulation, enables a more thorough investigation of neural circuit dynamics. We have designed a novel flexible neural implant capable of controlled, localized chemical stimulation and high-density electrophysiology recording. To minimize tissue damage and response, the neural probe was implemented with a small cross-sectional dimension using planar micromachining processes on Parylene C, a mechanically flexible, biocompatible substrate. The probe shank features two large microelectrodes (chemical sites) for drug loading and sixteen small microelectrodes for electrophysiology recording to monitor neuronal response to drug release. To reduce the impedance while keeping the size of the microelectrodes small, poly(3,4-ethylenedioxythiophene) (PEDOT) was electrochemically coated on recording microelectrodes. In addition, PEDOT ...
An ultra-compliant, scalable neural probe with molded biodissolvable delivery vehicle
2012
This paper describes an ultra-compliant parylene-platinum neural probe embedded in a biodissolvable delivery vehicle. High probe compliance is achieved using thin wires (width of 10.0 μm and thickness of 2.7 μm) and by meandering the probe. The insertion of the ultra-compliant probe is achieved by encasing it in a dissolvable delivery vehicle made from molded carboxy-methylcellulose. In vivo implantations of delivery vehicles with 1.5 mm long shanks, widths of 100 μm and 300 μm and a targeted thickness of 135 μm have been done through the dura in the cortex of Sprague-Dawley rats at a speed of 80 mm-s-1. The delivery vehicle becomes a gel over a period of less than three minutes, after which the handling portions of the delivery vehicle are removed leaving the shanks embedded in the brain.
Dextran as a Resorbable Coating Material for Flexible Neural Probes
Micromachines
In the quest for chronically reliable and bio-tolerable brain interfaces there has been a steady evolution towards the use of highly flexible, polymer-based electrode arrays. The reduced mechanical mismatch between implant and brain tissue has shown to reduce the evoked immune response, which in turn has a positive effect on signal stability and noise. Unfortunately, the low stiffness of the implants also has practical repercussions, making surgical insertion extremely difficult. In this work we explore the use of dextran as a coating material that temporarily stiffens the implant, preventing buckling during insertion. The mechanical properties of dextran coated neural probes are characterized, as well as the different parameters which influence the dissolution rate. Tuning parameters, such as coating thickness and molecular weight of the used dextran, allows customization of the stiffness and dissolution time to precisely match the user’s needs. Finally, the immunological response ...
Recent Advances in Materials, Devices, and Systems for Neural Interfaces
Advanced materials (Deerfield Beach, Fla.), 2018
Technologies capable of establishing intimate, long-lived optical/electrical interfaces to neural systems will play critical roles in neuroscience research and in the development of nonpharmacological treatments for neurological disorders. The development of high-density interfaces to 3D populations of neurons across entire tissue systems in living animals, including human subjects, represents a grand challenge for the field, where advanced biocompatible materials and engineered structures for electrodes and light emitters will be essential. This review summarizes recent progress in these directions, with an emphasis on the most promising demonstrated concepts, materials, devices, and systems. The article begins with an overview of electrode materials with enhanced electrical and/or mechanical performance, in forms ranging from planar films, to micro/nanostructured surfaces, to 3D porous frameworks and soft composites. Subsequent sections highlight integration with active materials ...
Fluidic Microactuation of Flexible Electrodes for Neural Recording
Ultra-flexible microelectrodes that can bend and flex with the natural movement of the brain reduce the inflammatory response and improve the stability of long-term neural recordings. However, current methods to implant these highly flexible electrodes rely on temporary stiffening agents that increase the electrode size thus aggravating neural damage during implantation, which leads to cell loss and glial activation that persists even after the stiffening agents are removed or dissolve. A method to deliver thin, ultra-flexible electrodes deep into neural tissue without increasing the stiffness or size of the electrodes will enable minimally invasive electrical recordings from within the brain. Here we show that specially designed microfluidic devices can apply a tension force to ultra-flexible electrodes that prevents buckling without increasing the thickness or stiffness of the electrode during implantation. Additionally, these fluidic microdrives allow us to precisely actuate the ...