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/ /f8R: 8PPitltllt tJ31! '51CE I 1. r&fer&nce 2: gate oxide 3: insulating resin b) 4: channnel S: s&urce ,., l •D: drain B: bulk •I <olut,on ' ',,, • I ' ' "' "'MDSFET ISFET Figure 7. An ISFET (Ion Sensitive Field Effect Transistor) Needle-Type pH Sensor for Monitoring Tissue Physiologic Status ( http : / /www. ee. sei kei. ac. j p/ ~se Iich i/ Iectu re/ Biom ed 1ca I/ 09/09- biosenso r. htm I) The sensor element is an ion sensitive field effect transistor (ISFET). This device is micromachined from silicon by using standard semiconductor photolithography processes. The actual active sensor surface is near the tip of the device where there is a thin film of silicon nitride covering the gate region of the transistor. The gate is sensitive to very small changes in electric field, and these in turn cause relatively large changes (or gain) in the current flow through the transistor. At the center in Figure 7 is a standard transistor diagram showing the gate and its relation to the other contacts. On the right is shown the pH sensitive ISFET system that measures an electric field change across the nitride membrane. The membrane is placed directly in contact with the liquid to be measured. It is not known the exact process that occurs at the membrane that gives rise to electric field shifts on the gate. Presumably hydrogen ions reversibly adsorb onto the interface between the nitride membrane and the solution causing local electric field changes on the gate. This device is not meant for permanent implantation but rather short term applications in research or medical surgery where the sensor is used over just a few hours. Proteins and other biological molecules adhere to the gate region of the ISFET and cause a slow 11 UNCLASSIFIED//FOA. OFFUiliR.k Wlili a,11,~·
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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.