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This Defense Intelligence Reference Document, dated 31 March 2010 and numbered DIA-08-1003-020, was prepared by the Defense Intelligence Agency's Defense Warning Office under its Advanced Aerospace Weapon System Applications Program. It surveys biosensors and biomedical microelectromechanical systems, covering brain-implanted micromachine neuroelectrodes, drug-delivery pumps, glucose sensors, neural interfaces, retinal prostheses, microfluidic lab chips, NASA cell-culture systems and microcantilever sensors. It concludes that the field is expanding rapidly, with nanomechanical systems expected to follow.
From the source: Release of 2026-09-18 Incident: 3/31/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys biosensors and BioMEMS, a broad class of miniature biomedical devices that combine microscale engineering with sensing, fluid handling, stimulation, or drug-delivery functions. The report reviews major application areas including implantable blood-chemistry sensors, neural interfaces, neurostimulation, drug-delivery pumps, microfluidic systems, and emerging nanoscale extensions of the field, while emphasizing that miniaturization can improve sensitivity and enable functions that are difficult or impossible at larger scales. However, it also makes clear that practical development is constrained by biocompatibility, long-term stability, sensor drift, device degradation inside the body, and the high regulatory burden associated with implantable medical systems. The document presents BioMEMS as a rapidly growing and productive field whose future advances are likely to come through continued improvements in fabrication, materials, and reliability.
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Only a few BioMEMS applications are well known for implanted devices and these are
used for positioning and repositioning of sensors. A specific example is application to
brain-electrode systems.
BRAIN-IMPLANTED BIOMEMS MICROMACHINE NEUROELECTRODES
There are applications in biomedicine and research where very small electrodes are
implanted into the brain. These microelectrodes are used in the cortex (surface layer)
to detect electrical activity associated with the volitional desire to move some part of
the body. Electrical activity is recorded as a very small change in voltage within the
tissue.
Near the top of the human head and about 2 cm beneath the scalp lie the parts of the
brain where nerve cells (neurons) are found which control the muscles of the body.
Specific locations in the cortex are associated with specific parts of the body. When a
person moves a limb, there can be detected a corresponding electrical activity of these
neurons. Neuroscientists have recorded these signals and developed a kind of map of
the brain that defines what brain ce lls actuate certain muscles of t he body.
An interesting phenomenon occurs in which some of these brain cells become active
even when t here is intent to move a limb but no actua l movement occurs. I n a healthy
person the intent to move can be detected by measurement of microvolt signals from
the brain cells about 120 milliseconds before any muscle movement occurs. In a person
who has lost a limb or has become para lyzed, the intent to move can still be detected in
the brain even though there is no limb movement.
Thus in principle there is an ability to electrically record from the brain and determ ine a
person's intent to move. Monitoring of the brain is accomplished by using an array of
implanted microelectrodes whose signals anticipate movement of specific limbs. These
signals can in turn be used to control machines. This is the idea beh ind advanced
devices that allow quadriplegics to interact with their environment. Signals from
implanted electrodes are used by computers to control robotic actuators.
A problem recording t he signals occurs because the body naturally tends to encapsulate
the electrodes with scar tissue, meaning the electrodes lose electrica l contact with the
neurons. A solution to this problem incorporates a very sma ll electromechan ical
actuator attached to the electrode. This device allows the implanted electrodes to
change their position occasionally in order to continue to monitor neural events. By
moving t he thin rod-like electrode up or down a small distance after several months of
implantation, the useful lifetime of the electrode array can be greatly extended.
The BioMEMS device described here is meant to be implanted under t he skull and on
top of the bra in cortex . It allows fine adjustment of less tha n a millimeter in order to
make sure the electrode system, once implanted, is able to contact the desired bra in
cells even after the electrode has been encapsu lated by scar tissue over t ime.
Figure 2 shows a photomicrograph of a gear-driven micromachine that was made
through collaboration between ASU and Sandia National Laboratories. The device is
driven by an electrostatic vibrating comb motor . Under a microscope it can be seen that
the combs move in an oscill atory fash ion at about 40 Hz when energized . Electrostatic
forces between two blade- like combs a few tens of microns apart are operative with
about 15 volts as the electric field source.
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Official release, from the pursue 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.