Documents / Report
This Defense Intelligence Agency reference document, dated 31 March 2010 (DIA-08-1003-020), was one of a series of advanced technology reports produced in FY 2009 under the Advanced Aerospace Weapon System Applications (AAWSA) program. It surveys biosensors and BioMEMS, covering brain-implanted neuroelectrodes, drug-delivery pumps, implantable glucose sensors, brain-machine interfaces, retinal prostheses, microfluidic lab chips, NASA cell culture systems, and microcantilever sensors. It concludes that the field is expanding rapidly toward nanomechanical systems.
UNCLASSIFIED/;'P8R: 8PPI8Iilrt l!Hili &HL>! Over the years, investigators have figured out how to interpret precursor bioelectrical events in the brain involved in planning of movements. The result is that if enough recording electrodes are placed in the brain in the motor cortex area, it is possible to determine planned muscle motion. This works even if the muscles ultimately do not move, as in the case of a quadriplegic with spinal cord injury. Thus quite a remarkable possibility presents in that a computer program can be taught to interpret large numbers of bioelectrodes signals and so can determine a person's intent to move and then, for example, control a robotic limb that actually performs the operation. Crude forms of these thought-controlled devices have been shown in research laboratories to be feasible, even if they are at present not practical. Among other things, the electrode interface to the brain is not yet sufficiently developed to provide large numbers of functioning electrodes that can work over prolonged periods of time. MICROELECTRODE ARRAY FABRICATION Neuroengineering applications in the brain can require tens to hundreds of electrodes to make contact with a similarly large numbers of cells in the brain. Large numbers of electrodes in arrays inserted into the surface of the brain cortex thus become sensitive to the timing and patterns of cell firings. BioMEMS has been a critical part of this development. The electrode array in Figure 20 is made by a electrochemical process of using a long but stiff wire that acts like a machine tool. Electrical discharge machining (EDM) is a process that makes use of computer-aided design (CAD), that runs under computer numerical control (CNC), and that is capable of batch processing. A block of titanium metal that will ultimately be the array is placed in an electrolyte solution and the working electrode initiates a submerged electrochemical arc. It finely removes metal by a chemical process that does not involve a lot of heat. It can generate intricate features with high aspect ratios and is capable of machining a large variety of conductive materials. In this case, the electrode shaft thicknesses are on the order of 50-100 microns and the entire device is less than a centimeter square with 96 electrode channels. When this device is encapsulated in a polymer at its base and pressed into the brain cortex, each electrode then records from a specific set of neurons that are local to its placement. 24 UNCLASSIFIED/ /P8"1 8PPll!l"'I! l!l!il! 8111!¥
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 45 pages are in the text index: search them above, or from the library's search.