Abstract:
A Microbolometer constructed of Biological and Non-Biological components, ing proteins with greater sensitivity to imaging, as the infrared radiation detectors.

Description:
RIGHTS OF THE GOVERNMENT 
     The invention described herein may be manufactured, used and licensed by or for the Government without the payment to me of any royalties thereon. 
    
    
     FIELD OF THE INVENTION 
     This invention is related to the field of uncooled infrared detector technology, and particularly thin film structures consisting of Biological and Non-Biological Components which have potential for high performance detector arrays comparable to cryogenically cooled detector arrays. It is anticipated protein detectors could be useful to long range applications and can replace high cost cooled detectors in the future. 
     BACKGROUND INFORMATION 
     Applicant&#39;s invention pertains to a Thermal Infrared Detector of the thin film resistance bolometer type, wherein infrared radiation (IR) incident on the Bolometer is absorbed, resulting in a temperature rise of the Bolometer Detector and therefore a change in the resistance of the Bolometer Detectors, which can then be transmitted or recorded by currently available electrical circuits. 
     Thin film infrared detector are described in U.S. Pat. Nos. 4,574,263, 4,116,063 and 3,069,644 using VO x  or semiconductive materials. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention is a new type of uncooled Microbolometer for use as an infrared detector. An increase in sensitivity over the currently available microbolometers is achieved by increasing the temperature coefficient of resistance (TCR), of the composition of the Microbolometer, by replacing vanadium oxide with selected proteins and/or DNA material in a device structure of silicon dioxide and silicon. 
     This new hybridized biological composition provides higher imaging sensitivity because of its higher temperature coefficient of resistance (TCR) properties defined as TCR=1/R (dR/dT) where R is the material resistance at the operating temperature TC. Routinely obtained TCR valves for VO x  are close to -3%/°C. but proteins and DNAs are expected to give higher TCR values of the order of +8 to +12%/°C. The low sheet resistance (˜1-2 ohms/square) of the proteins listed in the claims further reduces 1/f as well as Johnson noise giving higher resolution in thermal imagers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a representation of a single detector element. 
     FIG. 2 shows a sealing layer over the protein. 
     FIG. 3 shows a complete Bolometer construction. 
    
    
     DESCRIPTION OF THE INVENTION 
     The hybridized Biological Microbolometer consists of both Biological and Non-Biological components in which the agents responsible for transport of energy and sensing are electrons and/or ions. 
     Biological systems self-construct, they are compact, economical, fast, sensitive and their actions are very specific. 
     The infrared Detector is comprised essentially of a thin film of protein, selected from a list of temperature-sensitive proteins, prepared on a silicon dioxide/Silicon support structure. The thin film of protein is the infrared detector sensing element instead of VO x  or semiconductive materials. Each infrared detector device structure comprises a pixel or single detector element. Each infrared detector is connected to an electronic circuit for readout purposes, and in the case of a multi-dimensional monolithic array each infrared detector would be part of a more complex electronic readout system. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The substrate is a monocrystalline silicon wafer having a 1,0,0 surface orientation. 
     Referring to FIG. 1 it is seen that the protein sensor (10) has electrodes 11 and 12. The protein detector (10) is comprised of a two-dimensional array where a part of its readout electronics is directly underneath the detector pixel. Because of the low resistance of protein (˜1 ohm) the readout mechanism should be very fast when compared with inorganic bolometric arrays. Vanadium oxide or semiconductors have much higher resistance of the order of 1-100 kΩ. The conventional pixel size of protein bolometers is expected to be 50 microns square with a pitch of 50 microns and the array assembly is required to be packaged in an evacuated vessel. Each pixel is fabricated by depositing single or multi layers of proteins and etching the underlying material to produce a free standing bridge structure (as shown in H. Jerominek, et al,. SPIE Vol. 2746, 60-71). 
     This type of device structure is highly preferable in increasing detector performance because of the expected low thermal conductance of pixels. Proteins are deposited on the top of the oxidized silicons by spin coating techniques (as described in Bolton and J. R. Scherer, J. Phys Chem 1989, 93, 7635-7640). Spin coating technique reported preparation of 1-2 microns thick films of bovine serum albumin (BSA). In order to deposit a thin layer of proteins onto SiO 2  /Si structure, proteins solutions are simply adsorbed onto the oxidized silicon wafers. The leg metal is then deposited to connect protein pixels to the CMOS electronics. Oxidized silicon is also required to passivate proteins (shown in FIG. 2 as a sealing layer). The X- and Y- metals as shown in FIG. 1 are components of the CMOS circuits. 
     Names of 14 proteins considered useful are listed below: 
     Bovine Serum Albumin 
     Myoglobin 
     Cytochrome C 
     Cytochrome c551 
     Cytochrome b5 
     Plastocyanin 
     (2Fe--2S) ferredoxin 
     Catalase 
     Trypsin 
     Hemoglobin 
     Pepsin 
     Lysozyme 
     Ferripin 
     Alkaline Phosphatase 
     The Biological Microbolometer provides a higher imaging capability compared to vanadium oxide detecting elements because any protein that has a large dipole moment when folded in its native configuration undergoes a substantial change in conductivity when the native protein structure is significantly disrupted with temperature. DNA may even exhibit a sharp break in conductivity when it denatures, since it converts from a double-stranded helix to a random coil. 
     GC-rich DNAs are expected to give a much sharper break in conductivity than regular DNA because of the more rigid structure of GC rich DNAs in double helix.