Harvard University-Massachusetts Institute of Technology Division of Health Sciences and Technology and the Department of Electrical Engineering and Computer Science, Massachussetts Institute of Technology
A micromachined silicon technology is being developed for the purpose of sensing information from the stumps of amputated mammalian peripheral nerves. Information on long-term biocompatibility, anatomy, and physiology related to the structural design of this sensor is presented. Pertinent materials, fabrication, and surgical implantation issues are discussed. Noise, signal amplitude, and receptive field are considered as the prime determinants of the design of an appropriate electrode contact geometry for the structure. The selectivity of the device is also discussed in terms of the fine structure of the regenerated nerve. Examples of waveforms recorded from rabbit peripheral nerves using this sensor are presented and discussed in terms of electrical and physiological parameters. Possible use of the sensor as a source for a binary code suitable for communication of information to a computer is presented along with discussion of the limitations of the current technology and possible future applications.
"and their fibers. Neural spike signals can be used to control the movement of prosthetic limbs or other assistive robotics . Meanwhile, neural stimulation can mediate sensory feedback from sensors such as tactile, pressure, and force sensors to restore natural sensations with prosthetic limbs . "
[Show abstract][Hide abstract] ABSTRACT: A fully integrated minimally invasive compact polymer-based wireless neurostimulator was designed, fabricated, and characterized both in open air and in vivo. The neurostimulator (3.1 × 1.6 × 0.3 mm) consists of a planar spiral coil for wireless power supply through inductive coupling, two Schottky diodes for full-wave rectification, an application-specific integrated circuit neurostimulator circuit chip for stimulus spike signal generation, and two biphasic platinum-iridium (PtIr) stimulation electrodes. The device is fully integrated and completely embedded in biocompatible SU-8 packaging. For in vivo testing, the wireless neurostimulator was implanted subcutaneously in a rat hind limb. At the coupling power of 21 dBm (125 mW) at 394-MHz resonant frequency, stable and robust cortical responses during extended periods of wireless stimulation were recorded.
Journal of Microelectromechanical Systems 02/2013; 22(1):170-176. DOI:10.1109/JMEMS.2012.2221155 · 1.75 Impact Factor
"One important issue with MEAs designed for implantation applications is the difficulty in reliably and compactly connecting a high channel-count MEA to the necessary circuitry—the packaging challenge. As a result, most of the MEAs have only a modest number of wired signal channels –, which limits the amount of information that can be extracted from the nerve for high-resolution prosthetic limb control. On the other hand, because extracellular neural signals are very weak (in the range of microvolts) but background noises are high (e.g., the amplitude of EMG from adjacent muscles is in the range of millivolts), it is desired to put amplifiers close to the the recording sites to increase the signal-to-noise ratio (SNR), and to use multiplexing to cut down the number of wires needed. "
[Show abstract][Hide abstract] ABSTRACT: A high-resolution PDMS-based conformable microelectrode array (cMEA) with integrated electronics is implemented. The cMEA is incorporated into individual layers of a nanofiber-based nerve regeneration scaffold to create a novel regenerative electrode scaffold (RES) capable of establishing a stable, high-resolution peripheral nerve interface. The device features a compact size with an enhanced signal-to-noise ratio (SNR), as required by implantation applications. Preliminary characterizations of the device are performed using in vitro experimentations, including impedance spectroscopy and neural culturing.
Biomedical Circuits and Systems Conference (BioCAS), 2010 IEEE; 12/2010
"neurons and electronics for the stable detection of neural spike signals or for efficient stimulation of neurons and their fibers. Neural spike signals can be used to control the movement of prosthetic limbs or other assistive robotics . Neural stimulation can mediate sensory feedback from sensors such as tactile, pressure, and force sensors to restore natural sensations with prosthetic limbs . "
[Show abstract][Hide abstract] ABSTRACT: A biocompatible neural microprobe constructed using well-established SU-8 microfabrication techniques is described that was designed to record fiber spike signals from regenerated axons within peripheral nerves. These microprobes features bipolar longitudinal gold electrodes recessed below the surface within ldquogroovesrdquo designed to guide the growth of regenerating axons along the length of the grooves and limit the number of fibers that come in contact with the longitudinal electrodes. In addition, screening microprobe toxicity using cultures of human skin fibroblasts, the biocompatibility of these SU-8 microprobes for neural interface applications, in particular, was specifically verified using primary cultures of two sensitive cell types found in peripheral nerves: purified Schwann cells and explanted dorsal root ganglion (DRG) neurons and their fibers. The SU-8 microprobes were surgically implanted into transected rat Sciatic nerves within a unique peripheral nerve regeneration tube. Long-term fiber spike signals were recorded with these SU-8 microprobes in 13 chronically implanted rats for periods from 4 to 51 weeks without any signs of tissue damage or inflammatory reaction.
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