http://antonirogalski.com/wp-content/uploads/2011/12/Infrared-detectors-Status-and-trends.pdf

Infrared detectors: status and trends

To better address the functional consequences of inflammation on bronchial responsiveness, we studied two groups of BALB/c mice: a nonimmunized control group (n = 8) and a group immunized and chall...

Airway and tissue mechanics in a murine model of asthma: alveolar capsule vs. forced oscillations.

Optical sensor development has been pursued over past 25 years, which has also seen development of novel chemistries, materials, sensor designs and optical instrumentation. In addition, novel signal and data processing techniques have been adopted in the sensor development. New techniques and materials in chemical and biological sensing have set further stages of advanced research. One of the most recent technological advances in this area has been the development of optical nanosensors, which are sensors with dimensions on the nanometer scale. Nanosensors of various types (e.g. optical, electrochemical) have been published in the literature over the past decade. Optical nanosensors, like the larger and macro scale sensors, can be either chemical or biological, depending on the type of probe used. Both types of sensors have been studied to provide a reliable method of monitoring various chemicals in microscopic environments and have been used to detect molecules within single cells. The field of nanosensing is relatively new and reports in the literature presenting any problems associated with such a scale of analysis are sparse. This paper will briefly review some of the current developments in the field of optical nanosensors.

Optical sensors

In the paper, fundamental and technological issues associated with the development and exploitation of the most advanced infrared detector technologies are discussed. In this class of detectors both photon and thermal detectors are considered. Special attention is directed to HgCdTe ternary alloys on silicon, type-II superlattices, uncooled thermal bolometers, and novel uncooled micromechanical cantilever detectors. Despite serious competition from alternative technologies and slower progress than expected, HgCdTe is unlikely to be seriously challenged for high-performance applications, applications requiring multispectral capability and fast response. However, the nonuniformity is a serious problem in the case of LWIR and VLWIR HgCdTe detectors. In this context, it is predicted that type-II superlattice system seems to be an alternative to HgCdTe in long wavelength spectral region. In well established uncooled imaging, VOx microbolometer arrays are clearly the most used technology. In spite of successful commercialization of uncooled microbolometers, the infrared community is still searching for a platform for thermal imagers that combine aordability, convenience of operation, and excellent performance. Recent advances in microelectromechanical systems have led to the development of uncooled IR detectors operating as micromechanical thermal detectors. Between them the most important are biomaterial microcantilevers.

/pdf/infrared-detectors-for-the-future-1njpu9stwz.pdf

Infrared Detectors for the Future

Background: Lung disease in cystic fibrosis (CF) is established in early childhood with recurrent bacterial infections and inflammation. Using spirometry, the effect of this early lung damage cannot be measured until a child is 6 years of age when some irreversible lung damage may already have occurred. Techniques for measurement of lung function in infants and young children include raised volume rapid thoracic compression (RVRTC) and low frequency forced oscillation (LFFOT). The aim of this study was to investigate the role of inflammation and infection on a population of infants and young children with CF and to determine whether lung function in this population (measured by LFFOT) is affected by early lung disease. Methods: Lung function was measured by LFFOT in 24 children undergoing bronchoalveolar lavage (BAL) on 27 occasions as part of an annual programme while still under general anaesthesia. Following lung function testing, three aliquots of saline were instilled into the right middle or lower lobe. The first aliquot retrieved was processed for the detection of microbes, and the remaining aliquots were pooled to assess inflammatory markers (cytology, IL-8, NE, LTB 4 ). Results: Inflammation (percentage and number of neutrophils) was significantly higher in children with infections (p Conclusion: Infections and inflammation are established before symptoms are apparent. Inflammation is correlated with measures of parenchymal changes in lung function measured by LFFOT.

https://thorax.bmj.com/content/thoraxjnl/60/2/159.full.pdf

Correlation of forced oscillation technique in preschool children with cystic fibrosis with pulmonary inflammation.

Uncooled pyroelectric infrared detectors based on semiconducting Y–Ba–Cu–O have been investigated. Samples with four different structures were characterized. Two of the pyroelectric detectors were thermally isolated from the substrate by micromachining techniques for high optical sensitivity. Pyroelectricity was observed by the methods of optical illumination and direct substrate heating. A wide range of the values of pyroelectric coefficients was obtained with the maximum close to 20 μC/cm2 K in one device. Detectivities up to 108 cm Hz1/2/W were measured. The temperature dependence of these pyroelectric sensors was investigated. It was found that one device showed a fairly constant optical response with respect to temperature over a wide range around 300 K. However, responsivity of another device of a different geometry decreased sharply at ∼304 K. The spectral study of these devices showed that the wavelength-dependent response decreased when the silicon transmission increased. In addition, frontside i...

Micromachined YBaCuO capacitor structures as uncooled pyroelectric infrared detectors

This paper describes a new micromachining technique for fabrication of semiconducting yttrium barium copper oxide (YBCO) microbolometers using magnesium oxide (MgO) as the sacrificial layer. This type of bolometer can be operated at room temperature, providing a low-cost alternative for more expensive cryogenically cooled thermal detectors used for infrared (IR) imaging. The new micromachining techniques described here would enable the fabrication of YBCO IR focal plane array (FPA) with CMOS signal processing circuitry. Devices were fabricated by growing YBCO films on 4000-/spl Aring/-thick suspended Si/sub 3/N/sub 4/ membranes measuring 40/spl times/40 /spl mu/m/sup 2/ in area and extended over micromachined air gaps, which provide the low thermal conductivity that is required for high responsivity. The gap was created by etching an MgO sacrificial layer. This is the first example of using MgO in this type of application. The MgO sacrificial layer technique is fully CMOS compatible and presents no major fabrication challenges. Thermal conductivities achieved in vacuum with the Si/sub 3/N/sub 4/ suspended structures were on the order of 10/sup -7/ W/K, yielding an effective thermal isolation for bolometer operation. Optical characterization has shown responsivity up to 60 kV/W and detectivity over 10/sup 8/ cm.Hz/sup 1/2//W to black-body IR radiation, indicating that this technology is a suitable candidate for low-cost thermal imaging.

MgO sacrificial layer for micromachining uncooled Y-Ba-Cu-O IR microbolometers on Si/sub 3/N/sub 4/ bridges

This paper reports on the development of small pixel pitch infrared FPAs based on the capacitively read bimorph microcantilever sensor technology. The heat sensing bimorph microcantilever structures are fabricated directly onto the CMOS control and amplification electronics to produce a high performance, low cost imager that is compatible with standard silicon IC foundry processing and materials. Positional responsivities of greater than 0.3 μm/K have been modeled and measured for 50 μm pitch pixels, corresponding to a temperature coefficient of capacitance, DC/C, (equivalent to TCR for microbolometers) above 30%/K. This responsivity, along with noise capacitances in the sub-attofarad range and nominal sensor capacitances of 15 fF, give modeled NEDT < 20 mK for these devices. 
	At smaller pixel pitches, the positional responsivity decreases rapidly with feature size resulting in increased system NEDTs. Modeling the performance of microcantilever based IR sensors with innovative sensor structures and pixel pitches down to 17 μm indicates NEDTs < 20 mK and thermal time constants in the 5 msec range, are feasible with this technology. Results from detailed thermo-electro-opto-mechanical modeling of the operation of the 25 μm pitch pixels are presented.

High-sensitivity 25μm and 50μm pitch microcantilever IR imaging arrays

A study on the dielectric and pyroelectric properties of nonmetallic, polycrystalline Y—Ba—Cu—O thin films was performed for a range of temperatures (170–360K) and frequencies (2 Hz—1kHz). The complex permittivity, as a function of frequency, relaxed according to a first-order Debye Model. This relaxation was shown to be thermally activated, with an activation energy equal to the activation energy for the dc conduction of the material. The behavior of the data indicates that the polarization source is localized carriers near the Fermi level. Pyroelectricity was measured over a temperature range of 170–290 K, showing a constant response over these temperatures. Moreover, the pyroelectric properties of YBCO exhibited a strong sensitivity to poling at elevated temperatures, with a dramatic increase in the magnitude of the response. The pyroelectric coefficient changed from p ≈ 400 nC/(cm2-K) for the unpoled case to p ≈ 20 μC/(cm2-K) after poling with 5000 V/cm for one hour at 320 K.

Dielectric and pyroelectric response in Nb/semiconducting Y—Ba—Cu—O/Nb structures

This paper reports the fabrication of microbolometers using semiconducting YBaCuO as the IR sensing material. The detectors are operable at room temperature and thus are suitable for lost-cost and high performance imaging applications. Semiconducting YBaCuO is promising as a bolometric material as it has a thermal coefficient of resistance near 3% and relatively low noise. Two different bolometer structures will be reported here. First generation YBaCuO microbolometers were built on micromachined SiO 2 bridges using wet etching techniques to undercut the silicon. The second generation structures were processed upon micromachined Si 3 N 4 membranes with sputtered MgO films used as sacrificial layers. The membrane structures are the first of its kind to incorporate MgO as a sacrificial layer, and they offer a fabrication technique that is fully CMOS compatible, with all processing at ambient temperatures. Detectivities in the order of 10 8 cm Hz 1/2 /W were measured at 30 Hz chopping frequency in both structures. The thermal conductance of the suspended membranes was on the order of 10 -7 W/K, which is desirable as low thermal conductance yields high responsivities. There are realizable optimizations for both applications to yield detectivities over 10 9 cm Hz 1/2 /W. All measurements reported here were performed at ambient temperature with no temperature stabilization.

Semiconducting YBaCuO as infrared-detecting bolometers

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