CURRENT AND RECENT RESEARCH FUNDS AND AGENCIES SUPPORTING CADIFT ACTIVITIES

A.     CANADA RESEARCH CHAIR (TIER 1) IN DIFFUSION-WAVE SCIENCES AND TECHNOLOGIES

B.     2007 ONTARIO PREMIER’S DISCOVERY AWARD IN SCIENCE AND TECHNOLOGY

C.     NSERC DISCOVERY GRANT 2009 – 2014

The field of research of the Canada Research Chair and the other research projects, diffusion waves, has been largely developed by the nominee. Diffusion waves lack wave fronts, can’t be beamed, and don’t travel very far, yet they form the basis of several new and revolutionary measurement technologies (A. Mandelis, Physics Today 53, August 2000, p. 29). They exhibit unique depth-profilometric and subsurface imaging diagnostic capabilities, including a very wide range of physical fields and phenomena, among them thermal, electronic, photonic and atmospheric. They present outstanding trans-disciplinary research opportunities in the biomedical, dental and optoelectronic manufacturing sectors. The proposed objectives focus on high-impact research goals which cannot be addressed successfully by existing diagnostic techniques. They represent the outcome of several years of research into the physics and properties of diffusion waves.

RESEARCH PROJECTS

These research projects are at the center of the CADIFT ongoing research program, within our mandate to develop advanced interdisciplinary cutting-edge diagnostic techniques and instrumentation. The necessary equipment for all the projects is already in place as a result of CFI-ORF infrastructure and NSERC RTI awards made in 2006-2007. It has been supplemented with additional equipment purchased with NSERC CHRP and Strategic Grants in 2008 and 2009, respectively.

BIOMEDICAL PHOTOACOUSTICS, BIOSENSORS, BIOTHERMOPHOTONICS AND IMAGING

   1. Fourier-Domain Depth-Selective Bio-Photoacoustic Tomography (FD-PAT):  (Posters PhotoThermoAcoustic Imaging of Tissues, Photoacoustic Radar Imaging) Photoacoustic imaging modalities are internationally regarded as very promising complements or alternatives to conventional magnetic resonance imaging (MRI), positron emission tomography (PET), X-rays, ultrasound and optical ("biophotonic") imaging. They compete on cost, image depth recovery, imaging resolution, and/or imaging contrast. Studies indicate an outstanding photoacoustic contrast of 200 - 450 % between blood rich breast tumors and normal breast tissue by virtue of the strong hemoglobin absorption of laser light [1]. In a rapidly growing number of publications [2] researchers have concluded that this contrast level substantially exceeds any other endogenous tissue contrast currently utilized in clinical ultrasonics, MRI and X-ray mammography. Therefore, it is expected that biomedical photoacoustics will complement and possibly rival the diagnostic capabilities of MRI, at a fraction of the cost. A three-dimensional slice-by-slice (or "depth selective") Fourier-domain PA tomography (FD-PAT), a “photoacoustic radar”, has been developed in the CADIFT [3-5]. It is unique and unlike current pulsed-laser photoacoustic modalities. My 2007 CFI/ORF-funded Facility for Advanced Bioaphotoacoustics and Photoacoustic Microfluidics, aimed at developing biomedical photoacoustic and diffusion-wave biosensor technologies, has enabled the design and purchase of sophisticated PAT transducer arrays and a pulsed Nd:YAG laser to complement our PAT breast cancer imaging instrumentation. Based on our first-generation imager performance [4], the superior signal-to-noise ratio of Fourier-domain detection (at least as established in other biophotonic imaging fields, such as optical coherence tomography [6])), and the availability of simultaneous amplitude AND laser-intensity-independent phase images, are unique features of Fourier-domain biophotoacoustics of particular importance. They are without time-domain (pulsed-laser) counterparts. Our FD-PAT system can resolve noise-limited artificial sub-surface absorbers in chicken breasts down to ca. 2 cm below the surface [4,7]. To our knowledge, this is the deepest reported feature resolved with a single piezoelectric transducer todate.  Additional sensitivity to subsurface hemoglobin absorptions has been obtained and will be investigated, using a confocal arrangement with the laser beam focus located below the surface [4]. Following the successful implementation of single-wavelength rapid scanning FD-PAT imaging of tissue in vitro, a differential spectroscopic imaging variant will be investigated for contrast enhancement, with a reference wavelength located in the neighborhood of the isosbestic point of oxy-  and deoxy-hemoglobin (ca. 800 nm [8]). The goal is to assess the diagnostic capabilities of the FD-PAT imager with regard to depth and size of a blood-rich lesion of about 1 mm or less, as required for effective breast cancer screening and surgical removal. Our results show that this size of an absorber can be detected at ca. 2 cm below the surface in tissue phantoms and chicken breasts with a single laser beam and transducer. Further research will involve collaboration with Dr. A. Vitkin at Princess Margaret Hospital to design a pre-clinical prototype for in-vivo studies with breast cancer patients. Implementation of a clinical set-up will be subsequently developed through hardware and software modifications of existing commercial medical ultrasound imaging systems (e.g. Texas Instruments [9]) using FD-PAT technology.

2. Development of a noninvasive blood glucose biosensor: (Poster: Noninvasive blood glucose biosensor) Diabetes afflicts a large and growing number of people worldwide - over 2 million in Canada alone - costing the healthcare system over $13.2 billion/year. To manage this condition, and to reduce the risk of severe complications, patients check blood sugar levels up to five times a day to maintain physiological glucose concentration between 90 and 120 mg/dl. The standard technique for measurement of glucose concentration requires skin puncture to draw a small blood sample to be examined using a test strip and automated meter to report results. This technique provides accurate glucose concentration data, but frequent skin puncture is associated with significant discomfort and risk of infection. The significant efforts directed towards the development of noninvasive and minimally-invasive techniques for glucose monitoring over the past twenty years, have as yet yielded no completely noninvasive sensor [10]. I propose the development and characterization of a novel noninvasive glucose sensing modality [11] utilizing our expertise in depth-profilometric photothermal instrumentation and measurements. The proposed wavelength modulation photothermal technique [11] has strong potential for a real breakthrough in the decades-long search for a non-invasive non-contacting diabetes monitoring biosensor. It relies on differential absorption of radiation from recently-developed quantum cascade lasers, chosen to emit at the peak and at the baseline of the 9-10.5 mm glucose absorption band in tissue [12], and detection of blackbody emission photons in the mid-IR spectral band (~ 5 mm) away from the absorption region. The differential lock-in thermal-wave signal phase is independent of skin emissivity which varies with pigmentation and from person-to-person and can be measurably related to glucose concentration in the tissue specimen [11]. This technique may be applied for measurements of glucose concentration in the interstitial fluid (ISF) of the superficial skin layers to establish correlation with glucose concentration in the blood. In the context of ISF glucose measurements, it is well established that equilibrium with blood glucose is present and that interstitial glucose measurements can be used effectively to monitor 24-h glycaemic excursions [13]. Since it probes only one absorption band through its own generated IR emissions at two absorption wavelengths (maximum and minimum), self-referenced and in relative isolation from interfering tissue absorptions, it could become an absolute measure of glucose concentration. The successful outcome of this research will be a breakthrough for Canada in biotechnology and will measurably improve the quality of life of diabetics everywhere.

3. Development of a Thermophotonic Lock-in Dental Caries Imaging Technology: (Poster: Dental Caries Lock-in Imaging) In the past 10 years a combined modulated photothermal radiometric (PTR) and luminescence (LUM) methodology has been developed in the CADIFT as the first ever depth-profilometric non-invasive thermophotonic dental caries detection technique. The PTR signals generated using near infrared (659 and/or 830 nm) lasers exhibit depth-sensitive information corroborated by LUM signals from enamel and dentin hydroxyapatite. In the past few years our studies have been directed to detecting artificial and natural sub-surface lesions in human teeth. The major findings were: a) The simultaneous application of the two methods (PTR and LUM) produced the highest combined sensitivity and specificity in dental sub-surface demineralization detection to-date, superior to other methods, notably X-rays [14,15]. b) Bitewing X-radiographs showed no sign of lesion even for samples treated for 30 days with a partially saturated acidic buffer solution, whereas PTR/LUM exhibited considerably higher sensitivity to early (artificial) caries showing changes even after 6 hours of treatment [16]. This sets the stage for a potentially breakthrough thermophotonic dental subsurface caries imaging technology of the entire tooth to compete with, and possibly replace, today’s dental–office X-rays without the ionizing effects.

Research in early caries PTR diagnostic imaging modality by use of a mid-infrared (thermal) camera, funded by a 2006-07 NSERC-RTI and the Premier’s Discovery Award, has commenced. As an extension of frequency-domain photothermal radiometry, a novel dental imaging modality, thermophotonic lock-in imaging (TPLI), is introduced. This methodology uses photothermal wave principles and is capable of detecting early carious lesions and cracks on occlusal and approximal surfaces as well as early demineralization induced by artificial caries solutions. The increased light scattering and absorption within early carious lesions increases the thermal-wave amplitude and shifts the thermal-wave centroid, producing contrast between the carious lesion and the intact enamel in both amplitude and phase images. Samples with artificial demineralization and natural occlusal and approximal caries were examined in this study. Thermophotonic effective detection depth is controlled by the modulation frequency according to the well-known concept of thermal diffusion length. TPLI phase images are emissivity normalized and therefore insensitive to the presence of stains. Amplitude images, on the other hand, provide integrated information from deeper enamel regions. It was concluded that the results of our non-invasive, non-contacting imaging methodology exhibit higher sensitivity to very early demineralization than dental radiographs and are in agreement with the destructive transverse microradiography mineral density profiles [17]. Following the development of the new dental imaging technique and proof-of-principle with simple carious lesions, more complicated, clinically relevant cases will be addressed, such as interproximal lesions, root caries, enamel de- and re-mineralization cycles and caries generation at enamel-filling interfaces. Preliminary studies using laser line scans have been very promising [18]. The controlled frame rate of the camera will be used to fix the operating subsurface depth in the tooth from which emissions are received and thus optimize demineralization lesion contrast in PTR images.

4. Research and development of two analytical instrumentation techniques: Photoacoustic-luminescence (PTA-LUM) radar/sonar and photothermal-luminescence (PTR-LUM) radar for early osteoporotic bone loss and density variation diagnosis.

The Killam Foundation has awarded a two-year Fellowship to Andreas Mandelis

As a feasibility study toward developing a suitable laser infrared photothermal radiometric (PTR) technique combined with modulated luminescence (LUM) from bones as a first step toward a sensitive, portable, in-situ monitoring technology for non-invasive, non-contact  monitoring of changes in thermal, optical and structural properties of those bones known to be at risk for microgravity related osteoporosis, namely the wrist and calcaneus, to be used as a monitor of the onset of osteoporosis for microgravity environments in the first instance, with a view to subsequent adaptation of the technology to osteoporosis detection under normal Earth gravity.  This technology is highly desirable as an integral part of on-board autonomous medical care of the crew during long-haul space missions, to Mars or at the International Space Station.

(to be updated)

Fig. 1(a): (1) Schematic diagram of the bone loss monitoring system by photothermal radar is shown with function generator (A), delay generator (B), laser controller (C), diode laser (D) (660 nm, 100 mW), photodetector (E), infrared (IR) MCZT (HgCdZnTe) thermoelectrically-cooled detector (F) and DAQ card (G) (60MS/s). (2): Software lock-in amplifier (a: PTR, b: LUM, c: Reference signals, d: Phase Lock Loop and e: Low Pass filter). (3): Correlation signal processing (radar) algorithms are used to measure frequency dependent (<1 kHz) amplitude and phase of the (PTR, LUM) signal, (f, g), respectively (a: PTR, c: Ref. signals, h: Fast Fourier Transform (FFT), i: inverse -FFT*, j: Band Pass filter and k: inverse FFT). An optical fiber (LUM) and an infrared fluoride fiber (PTR) bundle (horizontal black arrow lines in (1)) are used to collect bone signals.

(to be updated)

Fig. 1(b): (1) Schematic diagram of the bone loss monitoring system by PTA radar detection is shown with function generator (A), delay generator (B), laser controller (C), diode laser (D) (850nm, 300 mW), ultrasonic transducer (H) (3.5 MHz) and DAQ card (G) (100MS/s). (2): Correlation signal processing algorithms are used to measure frequency dependent amplitude and phase of the PTA radar signal (a: Transducer signal, b: Reference signal, c: FFT, d: FFT*, e: Band Pass filter and f: inverse FFT).

5. The Development of Laser Radiometric and Luminescence Instrumentation for the Diagnosis and Assessment of Dental Caries:  (Posters: Dental Caries Detection System, PTR and LUM assessment of dental caries) a) An existing laser infrared radiometric (PTR) and modulated luminescence (LUM) instrument has been dedicated for dental caries diagnostics. A non-cooled mid-infrared photodetector has been added which will be convenient for clinical use at a dentist's office; b) Studies of highly controlled levels of demineralization caries and water content in human enamel are being performed toward a calibration chart for the technology. The PTR and LUM signals are being correlated with depth profilometric densitometry signals from transverse micro-radiography (TMR) and or micro-computed tomography (m-CT), in collaboration with Professor Ben Amaechi, University of Texas at San Antonio. These experiments are  providing sets of standardized PTR and LUM signals, which can be directly related to different degrees of demineralization and moisture content; c) Further studies are carried out on extracted human teeth to demonstrate sensitivity and specificity of the upgraded instrument to various cases of demineralization caries. The work has led to an assessment of the relative merits of PTR vs. LUM techniques vis-a-vis the reliable detection of sub-surface dental caries. The goal is to provide a quantitative basis for the early detection of dental caries. Besides the obvious potential benefits to oral health in Ontario and beyond, benefits to Ontario dental manufacturing industry are anticipated by generating in this work a laboratory prototype of a novel, clinically compatible, diagnostic apparatus for controlled and reliable measurements of the demineralized carious state. With the advent of fluoride in toothpastes and municipal water supplies there has been a decrease in decay on the smooth surfaces of the teeth. There is less decay developing between teeth that can be seen on a traditional dental x-ray. This combined with more conservative techniques for restoring teeth has lead to a rise in decay on the biting surfaces of molar and bicuspid teeth (back teeth). This type of decay is not detected with conventional techniques (x-rays and visual examination) until the lesions are extremely large. Our device will allow us to detect early signs of sub-surface demineralization and to continue to monitor lesions in a non-invasive fashion. Current projects in collaboration with the Department of Dentistry and the Institute for Biomaterials and Biomedical Engineering, University of Toronto,  involve research on acid-induced caries generation in dental enamel and the understanding of fundamental chemical diffusion and reaction phenomena leading to subsurface demineralization depth profiles. Mathematical models of these processes and their impact on the PTR/LUM signals are objects of active studies. 

NON-DESTRUCTIVE DIFFUSION-WAVE TECHNIQUES AND IMAGING FOR SEMICONDUCTORS AND OPTOELECTRONIC DEVICES

 6.  Silicon Heavy Metal Contamination Studies using Photo-Carrier Radiometry (PCR): (Poster: PhotoThermal Spectroscopy of Semiconductors , Photocarrier Radiometry - Metal Contamination Imaging) Metal contamination currently accounts for over 50% of the yield losses in the multibillion-dollar worldwide semiconductor integrated circuit device manufacturing industry. In recent years, photocarrier radiometry (PCR), a form of non-contact, non-destructive modulated near-infrared photoluminescence was introduced and developed at the CADIFT for contamination/defect monitoring of industrial Si wafers [19]. PCR is sensitive to enhanced photo-carrier recombination rates exhibited by wafers with electronic traps due to heavy-ion contamination or defects. The PCR resolution is laser-beam-size or electronic-carrier diffusion-length limited, whichever is larger at a fixed frequency. Recombination lifetime measurement techniques can be utilized to monitor the purity of silicon and are well-suited for sensitive contamination control instruments essential for wafer yield improvement [20]. Among them, the photocarrier diffusion-length measuring technique of SPV with its electrical (surface capacitance) detection character has become a standard wafer contamination monitoring technology. Our comparative PCR and SPV studies [21] have shown that PCR can resolve iron in silicon at concentrations at least 10¹¹ cm^-3 under much higher spatial resolution conditions (< 100 mm) than SPV (~ 1-10 mm) and without the need for critical electrode spacing (± 1-5 mm) control. However, in order to produce IR photon fluxes high enough to register measurable lock-in amplifier signals, PCR, like all optical carrier generation and detection techniques (notably, photoconductance [22]), must operate under medium-to-high-injection conditions, in the range of 10¹⁵ – 10¹⁸ photons/cm³, assuming unity quantum efficiency. Therefore, it is clear that PCR sensitivity must be enhanced by several orders of magnitude over the current InGaAs detector element used with our set-up. Typical low-injection levels are in the range of 10¹²–10¹⁴ cm⁻³ [23]. Our recently acquired near-IR photomultiplier (PMT) has 1x10⁶ gain, an ideal amplification factor bringing PCR sensitivity to the desired minimum level of 10¹² cm⁻³ and rivaling electrical techniques such as SPV. Fe-contaminated industrial Si wafers from KLA Tencor (San Jose, CA) will be scanned following SPV measurements to determine sensitivity and resolution limits for [Fe] and [Cu] contamination monitoring. Low-injection PCR will be the first non-contact semiconductor diagnostic technology featuring unprecedented sensitivity similar to electrical metrologies, but with superior spatial-resolution. This makes possible future PCR scanning imaging of heavy metal contamination of entire wafer surfaces at a much higher resolution and significantly lower cost than SPV technologies.

7.  Photonic technology for nanolayer characterization: (Poster: PCR Technology for Nanolayer Characterization) SOI technology has been expanding rapidly, because fully or partially depleted devices fabricated in ultrathin Si layers ranging from 50 to 200 nm in thickness can prevent stray capacitance, which allows fabrication of metal oxide semiconductor field-effect transistors (MOSFETs) capable of high-speed operation with low power consumption as demanded by today’s fast computer technologies. The electronic quality of the top Si layer directly affects the device performance and yield. Advances in the production technology of SOI wafers with high crystalline quality have led to an increasing need for sensitive and nondestructive characterization methods for nanothin Si layers [24]. To accomplish this, our 355-nm UV laser will be used as the photocarrier-wave excitation source with the infrared PMT as the detector. The absorption coefficient of Si at 355 nm is 2.74x10⁵ cm^-1 [25], corresponding to an optical absorption depth of 30 nm. Following preliminary measurements in the CADIFT with longer wavelength lasers (532 and 830 nm) we concluded that the key determining factor for PCR diagnostic measurements within the SOI nanolayer is that no optical leakage should be transmitted down to the Si underlayer. These conclusions are supported by recent pulsed nitrogen laser measurements using microwave photoconductivity [26]. Lifetimes in SOI layers are extremely short (10 ns – 400 ns [26]) and controlled by nanolayer defects, surface and interface recombination rates. Therefore, the thickness-integrated PCR signals from SOI nanolayers are expected to be extremely low because the amplitude of the signal is directly proportional to the net recombination lifetime of the carrier [27]. The use of the near-IR PMT will be essential in the lock-in detection of the signal as the 10⁶ gain (amplification) of this instrument will compensate for the expected 2-5 order-of-magnitude decrease in PCR amplitude from that of bulk Si wafers (lifetimes: 1 ms – 10 ms). The delivery of sample matrices with various SOI thicknesses and doping concentrations of, e.g. p⁺Si:B, from KLA Tencor is under way.

8. Development of High-Frequency Lock-in Carrierographic (LIC) Imaging of Solar Cells: (Poster: Lock-in Carrierographic Imaging of Solar Cells ) dc photoluminescence (PL) imaging is the technique closest to providing an all-optical NDE of Si solar cells. However, it lacks contrast, spatial and depth (axial) resolution, particularly within the range of the p-n junction depth [28], which is of central importance for optimized solar-cell design, owing to the rapidly diffusing photocarriers. It is also hard to quantify the origin(s) of PL signal variations. Furthermore, it cannot provide information on optoelectronic kinetics of surface and subsurface regions. Thus, PL imaging is mostly used to detect problems associated with mechanical defects and cracks of raw substrates and solar cell devices. Electroluminescence (EL) yields information similar to PL, however, it is a contacting electro-optical method, has no depth profiling capability and requires completed operational electroded solar cells; it cannot be applied to substrates or partly processed devices. LIT is just emerging as a solar-cell imaging methodology and has several advantages due to its lock-in character. It provides thermal contrast images of local heat sources generated by mechanisms such as path resistance and carrier recombination at mechanical defects and crystalline boundaries [29].

(to be updated)

Fig. 1.

9. Development of Non-Contact Infrared Photo-Carrier Radiometry for Si-wafer Process Control: (Poster: Photovoltage Characteristics of Solar Cells) Fundamental case-study research is being carried out in order to assess the potential of a newly developed optoelectronic technique for semiconductor electronic defect diagnostics (named "Photo-Carrier Radiometry", PCR, by the Principal Investigator and CADIFT researchers) as a powerful quality control tool for the semiconductor industry. PCR is a major improvement over existing semiconductor inspection methods due to its non-contact character and signal content exclusively sensitive to electronic processes in the material. The project uses substrate and processed industrial silicon wafers from three partners. The proposed research is based on two major recent developments in our Laboratory: 1) The successful elimination of all thermal infrared emissions from infrared radiometric signals obtained from laser photoexcited free electronic carriers and capture of electronic recombination emissions in defect states only. 2) The new technique has revealed for the first time substantial influence of remote deep-lying electronic defects on front-surface electronic properties where devices are built. Based on these promising unique attributes of PCR, this technique is being developed in two directions: A) toward a silicon-industry quality control methodology, by exploring its potential to monitor and quantitatively measure wafer resistivity, carrier mobility, ion-implantation damage and shallow junction formation (doping); and B) as a wafer imaging tool through studies of doping contrast and concentrations in epitaxial layers on silicon and within the context of the ubiquitous heavy ion (Fe and/or Cu) contamination problem of today's industrial silicon wafers. These studies are aimed at assessing a reasonably broad spectrum of PCR potential applications over one industrial partner's (Photo-Thermal Diagnostics, Inc., Toronto) [link to http://www.ptdiagnostics.com] current Photo-Thermal Radiometry (PTR) wafer inspection technology. A new project on developing PCR instrumentation and measurement techniques for non-contact, non-destructive optoelectronic characterization of industrial solar cells (polycrystalline silicon) has been undertaken with Enfoton, an industrial partner in Lefkosia, Cyprus in conjunction with the Cyprus Institute. A successful project demonstrating PCR's capability to perform and compete well with the conventional metrologies in the foregoing application areas will propel PCR to the forefront of industrial semiconductor inspection technologies.

NON-DESTRUCTIVE EVALUATION OF INDUSTRIAL MATERIALS AND PROCESSES, THERMOPHYSICS INSTRUMENTS AND MEASUREMENTS

10.   Crack monitoring in green sprockets by non-destructive laser Photothermal Radiometry (PTR): (Poster: Crack monitoring by non-destructive PTR) Preliminary results had indicated that photothermal radiometry has strong potential as a non-destructive testing (NDT) technology to monitor cracks in sintered and unsintered (green) powdered metal components and parts. As there is no other known methodology to diagnose these cracks at the green state, based on these positive findings Stackpole has proposed to pursue a more thorough investigation of the scientific and technical aspects and capabilities of PTR signal generation and speed and procedures of data acquisition as a next phase. Therefore, the purpose of this Project is to further examine PTR in this particular application by obtaining a better theoretical understanding of the physical origins of PTR signal generation from regions of thermal-wave confinement, such as right-angled corners and curvatures with the goal to optimize the parameters responsible for the PTR response (laser beam size, angular-step size, modulation frequency and rotation speed). Also, a mathematical model of the thermal-wave signal from geometries akin to the inner corner of the sprocket will be developed and simulations will be made. The PTR method reproducibility and reliability, the limitations of the technique in monitoring cracks during measurements at discrete random angular intervals around the sprocket inner corner, and the effects of rotational speed on signal quality will be examined.  The eventual goal is to move to an in-line or off-line inspection tool which will be able to meet Stackpole production speed requirements by establishing an acceptable minimum crack scan contrast yield, a function of scanning speed and crack size. The fact that in our preliminary measurements PTR has been sensitive enough to identify cracks in green samples, both clutch-plate rings and sprockets, is already a major advance, as there are no other non-destructive techniques available for this type of inspection to-date. When signal generation is thoroughly understood using suitable green sprocket samples supplied by Stackpole to the CADIFT, signal contrast optimization for circumferential cracks (the results of the proposed Project) is expected to lead to the development of a full on-line or off-line inspection technology, depending on the speed of data acquisition for acceptable crack identification yields. A preliminary estimate of the speed of data acquisition based on the parameters that limit scanning speed (both instrumental and crack-related) will be obtained in this Project. It is likely that the developed inspection technique can be more widely applied to other Stackpole and similar industrial products. At the same time, the post-doctoral researchers engaged in the project will acquire much needed familiarity with advanced instrumentation, both hardware and software, of relevance to Ontario industry which makes them a unique asset at the crucial interface between University research and Industrial needs.

11.  A Prototype Instrument for Non-Contact Hardness and Case-Depth Inspection of Industrial Steels using Laser Infrared Photothermal Radiometric Technology:  (Poster: Thermal Wave Radar, Non-contact hardness and case-depth inspection PTR instrumentation) We have been developing an industrial prototype for non-contact, non-intrusive inspection of case-hardened manufactured industrial steel products. The prototype is based on our patented laser photothermal radiometric (PTR) depth-profilometry method as applied to heat-treated steel inspection procedures. The undertaken Market Readiness program follows results obtained from extensive studies on PTR case depth characterization of several types of C-1018 heat-treated steels (hexagonal, cylindrical, spherical heads) from Metex Heat Treating Ltd. In addition, an R&D study of PTR signal sensitivity to the state of the material in green (unprocessed), hardened and quenched, and tempered steels will be undertaken, with a view to expanding the utility of the PTR technology to sorting of the state of hardness of steel products. The projected benefits to Ontario's (and global) steel industry are the potential for product yield enhancement and a competitive edge in manufacturing speed with the potential of 100% inspection, fast and non-destructive quality control monitoring of the heat treating process. These are distinct advantages over today's state-of-the-art destructive indenter probes.

12.  Ultrasensitive thermophysical photopyroelectric liquid contamination sensor: (Poster: Thermal-Wave Cavity Sensor)A novel technique for ultra-high resolution thermal diffusivity measurements of liquid mixtures has been introduced, which can eventually be implemented into an in-situ water-pollution monitoring device. In this technique, a thermal-wave resonant cavity [34] (TWRC) containing a liquid sample is utilized. A thermal-wave generator (TWG) and a pyroelectric sensor bound the liquid layer from both sides thus forming the cavity walls. The TWG (Aluminum film) converts the optical energy of a broad modulated laser beam into thermal waves. The induced temperature oscillations are conducted into the liquid and are detected by the sensor (PVDF film) producing an output signal. The thermal diffusivity evaluation by means of the TWRC involves the fitting of the experimental cavity-scan data set as a function of modulation frequency. A conduction-radiation theoretical model of the one-dimensional thermal-wave field within the cavity was developed and compared with experiments [35], showing excellent agreement. Unlike the straight-line behavior predicted by a purely conductive mechanism [34], the amplitude and phase saturate beyond a certain modulation frequency, as the thermal diffusion depth decreases and radiation heat transfer across the cavity starts to dominate. The best-obtained resolution of the frequency scan method is 0.5 % v/v of methanol in water. To improve on the level of sensitivity, we applied a novel signal baseline suppression scheme [36] known as “common-mode rejection demodulation” (CMRD).  In this scheme, the lock-in amplifier integrates the output of the experimental system driven by a bimodal pulse excitation over a single modulation period (a sub-harmonic waveform excitation). The output is the difference between the response waves produced by each one of two pulses, so the background signal is eliminated. The improved method [37] shows resolution up to 0.2% v/v methanol in water, the best resolution in thermal diffusivity measurements reported in literature to-date, to our best knowledge. The ultra-high sensitivity of the method can be especially useful in environmental applications, specifically in water pollutions monitoring.

REFERENCES

[1]  A. A. Oraevsky et al., Proc. SPIE 3597: “Biomedical Optoacoustics” p. 352 (1999); V. G. Andreev et al. Proc. SPIE 3916: “Biomedical Optoacoustics”, p. 36 (2000).

[2]  See Society for Optical Engineering (SPIE): “Biomedical Optoacoustics” Vols. 3916 (2000); 4256 (2001); 4618 (2002); 4960 (2003); “Photons plus Ultrasound” Vols. 5320 (2004); 5697 (2005); 6086 (2006); 6437 (2007) (A. Oraevsky and L. Wang, eds.)

[3] “Laser Photo-Thermo-Acoustic Imaging Frequency-Swept Heterodyne Lock-in Instrumentation for Industrial and Biomedical Materials”, Inventors: A. Mandelis et al., US patent submitted February 2005.

[4] S. A. Telenkov and A. Mandelis, J. Biomed. Opt. 11, 044006 (2006).

[5]  Y. Fan, G. Spirou, A. Mandelis and I. A. Vitkin, J. Acoust. Soc. Am. 116, 3523 (2004); Y. Fan, A. Mandelis et al., Phys. Rev. E  72, 051908 (2005).

[6]  M. A. Choma et al. Opt. Express 11, 2183 (2003); R. Leitgeb et al., Opt. Express 11, 889 (2003); G. Hausler and M. W. Lindner, J. Biomed. Opt. 3, 21 (1998); J. F. de Boer et al. Opt. Lett. 28, 2067 (2003).

[7] A. Mandelis “Bioacoustophotonic Depth-Selective Imaging of Turbid Media and Tissues: Instrumentation and Measurements”, Physics in Canada, Special Issue on Instrumentation and Measurement Physics, Vol. 62, 83 (2006).

[8] S. Prahl, “Optical Absorption of Hemoglobin”, http://omlc.ogi.edu/spectra/hemoglobin/index.html

[9] http://focus.ti.com/docs/solution/folders/print/346.html

[10]  R. J. McNichols and G. L. Cote, J. Biomed. Opt. 5, 5 (2000).

[11] “Non-invasive Biothermophotonic Sensor for Blood Glucose Monitoring “, Inventors:  A. Mandelis, S. Telenkov, US patent submitted March 2006.

[12]  C.J. Pouchert (1981), The Aldrich Library of Infrared Spectra, 3rd. ed., Aldrich Chemical Co.

[13]  A. C. Guyton and J. E. Hall, “Textbook of Medical Physiology” 10th ed. Philadelphia, Ch. 78 (2000).

[14]  R. J. Jeon, C. Han, A. Mandelis, V. Sanchez and S. H. Abrams, Caries Res. 38, 497 (2004).

[15]  R. Jeon, A. Mandelis, V. Sanchez and S. H. Abrams , J. Biomed. Opt., 9, 804 (2004).

[16]  R. J. Jeon, A. Mandelis et al., J. Biomed. Opt. 12, 034028 (2007).

[17]  A. Tabatabei, A. Mandelis and B. T. Amaechi, “Thermophotonic lock-in imaging of early demineralized and carious lesions in human teeth”, J. Biomed. Opt. (In press; accepted August 2010).

[18]  R. J. Jeon, A. Hellen, A. Matvienko, A. Mandelis, S. H. Abrams and B. T. Amaechi,  J. Biomed. Opt. J. Biomed. Opt. 13 (3) , 034025 May/June 2008.

 [19]  A. Mandelis et al.  Phys. Rev. B67, 205208 (2003); Appl. Phys. Lett. 85, 1713 (2004); Appl. Phys. Lett. 82, 4077 (2003)].

[20]  G. Zoth, in Recombination Lifetime Measurements in Silicon, ASTM STP 1340, edited by D.C. Gupta, F.R. Bacher, and W.M. Hughes (American Society for Testing Materials, 1998), p.30.

[21]  D. Shaughnessy and A. Mandelis, J. Electrochem. Soc. 153, G283 (2006).

[22]  D. K. Schroder, “Semiconductor Material and Device Characterization”, Wiley, New York (1998), Chap. 9.

[23]  G. Zoth and W. Bergholz, J. Appl. Phys. 67, 6764 (1990).

[24]   J. P. Collinge, Silicon-on-Insulator Technology: Materials to VLSI, 2nd Ed., Kluwer Academic, Boston (1997).

[25]  E. D. Palik, Handbook of Optical Constants of Solids III (Academic, New York, 1998), p. 536.

[26] S. Sumie, F. Ojima, K. Yamashita, K. Iba and H. Hashizume, J. Electrochem. Soc. 152, G99 (2005).

[27]    B. Li, D. Shaughnessy, A. Mandelis, J. Batista and J. Garcia, J. Appl. Phys. 95, 7832 (2004).

[28] T. Fuyaki, H. Kondo, Y Takahashi, Y. Uraoka, Appl. Phys. Lett. 86, 262108 (2005).

[29] M. Abbott, J. Cotter, F. Chen, T. Trupke, R. Bardos, and K. Fisher, J. Appl. Phys., 100, 114514 (2006).

[30] A. Melnikov, A. Mandelis, J. Tolev, P. Chen, and S. Huq, J. Appl. Phys., 107, 114513 (2010).

[31] A. Mandelis, A. Melnikov, J. Tolev, J. Xia, et al., ”Non-destructive infrared optoelectronic lock-in carrierography of mc-Si solar cells”, Quant. Infra Red Thermogr. (QIRT) J. 7 35-54 (2010).

[32] S. Grauby, B. C. Forget, S. Hole and D. Fournier, Rev. Sci. Instrum. 70, 3603-3608 (1999).

[33] A. Mandelis, “Diffusion-Wave Fields: Mathematical Methods and Green Functions”, Springer-Verlag, New York (2001), Chap. 9.

[34]  J.Shen and A.Mandelis, Rev.Sci.Instrum. 66, 4999 (1995).

[35]  A. Matvienko and A. Mandelis, Int.J. Thermophys, 26, 837 (2005).

[36]  A.Mandelis, S.Paoloni, L.Nicolaides, Rev.Sci.Instrum. 71, 2440 (2000).

[37]  A. Matvienko and A .Mandelis, Rev.Sci.Instrum. 76, 104901 (2005).