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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Photoacoustic Spectroscopy Sensor with a Small-Gap Quartz Tuning Fork
摘要： Quartz tuning fork (QTF), a mature electric device which is widely used in electronic circuits for timing reference, has been investigated in photoacoustic spectroscopy in recent years. Due to the excellent immunity, high Q-factor, and compactness, utilizing a QTF for acoustic wave detection in photoacoustic spectroscopy, namely quartz-enhanced photoacoustic spectroscopy (QEPAS), is a significant innovative spectroscopy. In a QEPAS system, the QTF’s distance of the fork tines, the so-called gap, determines the space for acoustic wave generation. Traditional QTFs with a gap of 300 μm can satisfy the requirement when the excitation source which locates in the near-infrared spectrum range. While, some custom-made QTFs has been investigated to accommodate the mid-infrared laser with beam larger than ~400-500 μm [1,2]. Nevertheless, in the near-infrared range, the diameter of the laser beam is far smaller than that in the mid-infrared spectral range. When a QTF applied in the QEPAS system, the laser beam passes through the fork valley and excites the gas molecules. Notably, the acoustic wave generated by the reaction between the laser beam and the gas molecules can be viewed as spherical wave oscillation. The spherical wave propagation decreases with the cube of the distance, which suggests that the energy of the sound wave will diminish rapidly as the distance from the generation source point of the sound wave increases. So, employing a small-gap QTF can avoid energy losses and therefore improve the signal level of the QEPAS sensor. In this paper, a custom-made QTF with a small-gap of 200 μm used in the QEPAS sensor was demonstrated. A simulation of the optimal vertical position with respect to the QTF and the length of micro-resonator were developed by using the COMSOL Multiphysics. The experiment was also conducted and indicated that such a small-gap QTF has an improved performance in the QEPAS sensor system.
关键词： photoacoustic spectroscopy,acoustic wave detection,QEPAS,quartz tuning fork,small-gap
更新于2025-09-12 10:27:22
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In Vivo Reflection-Mode Photoacoustic Microscopy Enhanced by Plasmonic Sensing with an Acoustic Cavity
摘要： Relying on high-sensitivity refractive index sensing and a highly constrained evanescent field of surface plasmon resonance (SPR), broadband photoacoustic (PA) pressure transients were measured using an SPR sensor instead of routinely used piezoelectric ultrasonic transducers. An acoustic cavity made from stainless steel and having a designed ellipsoidal inner surface redirected laser-induced PA waves from the PA excitation spot to the SPR sensor. By incorporating the SPR sensor with the acoustic cavity, we developed optical-resolution photoacoustic microscopy (OR-PAM) with multiple advantages, including reflection-mode signal capture, improved PA detection sensitivity, increased PA spectral bandwidth as broad as ～98 MHz, and micrometer-scale lateral resolution. This allowed label-free volumetric PA imaging of vasculature in not only the thin ear but also the thick forelimb of living mice. With these combined advantages, our OR-PAM system potentially offers more opportunities for biomedical investigation, for example, when studying microcirculations in the eye and cortex.
关键词： reflection mode,high sensitivity,surface plasmon resonance,in vivo vascular imaging,photoacoustic imaging
更新于2025-09-12 10:27:22
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LED-based photoacoustic imaging for monitoring angiogenesis in fibrin scaffolds
摘要： Vascularization of engineered constructs is required to integrate an implant within the host blood supply. The ability to non‐invasively monitor neovascularization of an implanted construct is ultimately critical for translation. Laser speckle contrast analysis (LASCA), a widely used imaging technique within regenerative medicine, has high spatial resolution but offers limited imaging depth and is only sensitive to perfused blood vessels. As an emerging technology, photoacoustic (PA) imaging can provide centimeters of imaging depth and excellent sensitivity in vascular mapping. PA imaging in combination with conventional ultrasound (US) imaging offers a potential solution to this challenge in regenerative medicine. In this work, we used an LED‐based PA‐US dual system to image and monitor angiogenesis over 7 days in fibrin‐based scaffolds subcutaneously implanted in mice. Scaffolds, with or without basic fibroblast growth factor (bFGF), were imaged on day 0 (i.e., post implantation), 1, 3, and 7 with both LASCA and PA‐US imaging systems. Quantified perfusion measured by LASCA and PA imaging were compared with histologically‐determined blood vessel density on day 7. Vessel density corroborated with changes in perfusion measured by both LASCA and PA. Unlike LASCA, PA imaging enabled delineation of differences in neovascularization in the upper and the lower regions of the scaffold. Overall, this study has demonstrated that PA imaging could be a non‐invasive and highly sensitive method for monitoring vascularization at depth in regenerative applications.
关键词： Photoacoustic Imaging,LED-based Imaging,Fibrin Scaffolds,Tissue Engineering,Angiogenesis
更新于2025-09-11 14:15:04
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Application of MEMS Enabled Excitation and Detection Schemes to Photoacoustic Imaging
摘要： This paper shows, for the first time, a MEMS enabled photoacoustic system, using a custom MEMS Q-switched Nd:YAG laser for generation of photoacoustic (PA) waves and a custom-built MEMS thin-film aluminium nitride piezoelectric micromachined ultrasound transducers for PA wave detection.
关键词： Photoacoustic,Miniaturisation,PMUT,Aluminium Nitride,MEMS,Imaging,Q-switched Nd:YAG
更新于2025-09-11 14:15:04
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Development of a compact laser-diode based frequency domain photoacoustic sensing system: Application of human breast cancer diagnosis
摘要： We present the development of a laser diode based photoacoustic spectral response (PASR) setup capable of diagnosing human breast cancer tissues through the use of mechanobiological properties of the tissue. A detailed description of the laser driver is provided, highlighting the important characteristics of the developed driver. Furthermore, the amplifier development is described. The developed laser diode based PASR system has been characterized using standard samples. Subsequently, the developed experiment has been applied onto diagnosis of human breast tumors. Energy has been used as a parameter to differentiate between normal and malignant tissues. The results were statistically consistent and then compared with standard histopathology for correlation.
关键词： photoacoustic spectral response,breast cancer diagnosis,laser diode,mechanobiological properties
更新于2025-09-11 14:15:04
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A Self-Adaptive Model for the Prediction of Soil Organic Matter Using Mid-Infrared Photoacoustic Spectroscopy
摘要： Fast quantification of soil organic matter (SOM) is important in crop production and soil fertility evaluation. Fourier-transform infrared (FTIR) spectroscopy has been widely utilized for rapid, cost-effective, and non-destructive SOM determination. However, the lack of accuracy has limited the application of FTIR spectroscopy to quantitative SOM prediction because the models are built from a typical database, resulting in large errors in new independent samples. In this study, using 933 paddy soil samples collected in Lishui, China, a “self-adaptive” model was designed for predicting SOM content, in conjunction with Fourier-transform mid-infrared photoacoustic spectroscopy (FTIR-PAS). The resulting FTIR-PAS spectra afforded abundant soil information, reflected in O–H, N–H, and C–H vibrations (4000–2800 cm?1), C=O and C–H vibrations (2500–1200 cm?1), and the fingerprint region (1200–500 cm?1). The self-adaptive model was established by: (i) identification of soil samples, selected by Euclidean distance, with soil spectra to similar the target (unknown) soil sample and ranking of the Euclidean distance values in ascending order; (ii) selection of the optimal parameters to build a partial least squares (PLS) model based on an optimal calibration sample subset; and (iii) prediction and validation of the unknown soil sample. The predictive capabilities of the self-adaptive model and conventional PLS model were compared; the self-adaptive and conventional PLS models had R2 values of 0.9293 and 0.5796, root mean square errors of prediction of 1.65 and 3.26 g kg?1, and ratios of percentage deviation (RPD) of 3.18 and 1.62, respectively. Therefore, the self-adaptive model showed greater potential for application, having significantly enhanced applicability while improving the accuracy of prediction.
关键词： Fourier-transform mid-infrared photoacoustic spectroscopy,partial least squares,paddy soils,self-adaptive model,soil organic matter
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Compact Photoacoustic Spectrometer Based on a Widely Tunable Mid-Infrared Pulsed Optical Parametric Oscillator
摘要： For highly sensitive and selective photoacoustic (PA) trace-gas sensing it is desirable to use high power light sources with large wavelength tunability in the mid-infrared (MIR) region, where most molecules have strong vibrational transitions. The OPO technology is an old technology, but still an excellent choice as light source for PA spectroscopy. The advantages are their molecular specificity due to large wavelength tunability (1.5 to 5μm), high energy output, cost-effectiveness and compactness [1]. The tunability of OPOs together with PA allow for multi-gas detection of several components with common signal processing and data analysis. MIR OPOs can operate in different configurations both pulsed and continuous wave (CW). The pulsed operation results in high peak power, potentially nonlinear absorption effects and a normalized noise equivalent absorption that is not extreme. We demonstrate a novel miniaturized PA trace gas analyzer platform integrated with a MIR OPO targeting the major market opportunity of environmental monitoring and breath analysis [2,3]. We demonstrate that a miniaturized photoacoustic spectroscopic (PAS) cell can be excited resonantly with the MIR OPO by adjusting the laser pulse repetition rate to match the acoustic resonance of the PAS cell. The application of the gas sensor for real time environmental measurements and breath analysis is demonstrated using three samples of gas concentration; 100 ppmV of methane (CH4), 100 ppmV of nitrogen dioxide (NO2), and approximately 1000 ppmV ammonia (NH3) in atmospheric air with a humidity of 40% [3]. A gas flow rate of 300 ml/min through the PAS cell was applied for the three samples. These gases are well-known environmental trace gases and biomarkers in exhaled breath. The gases cause environmental degradation through their effects on soil acidification, eutrophication, and stratospheric ozone depletion. The presence of ammonia in the environment is mainly due to the degradation of animal waste, industrial processes and diesel exhaust. NO2 is a toxic gas and a regulated air pollutant that possess a serious risk for human health. Monitoring them in human breath is also particularly relevant as they are potential cancer biomarkers. We acknowledge the financial support from EUREKA (Eurostars program: E10589 - PIRMAH) and the Danish Agency for Higher Education.
关键词： photoacoustic spectroscopy,optical parametric oscillator,breath analysis,trace-gas sensing,mid-infrared,environmental monitoring
更新于2025-09-11 14:15:04
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Effect of doping mechanism on photogenerated carriers behavior in Cu-doped ZnSe/ZnS/L-Cys core-shell quantum dots
摘要： Cu-doped ZnSe/ZnS/L-Cys core–shell QDs are prepared by both nucleation doping and growth doping in an aqueous synthesis method. Transport of photogenerated free charge carriers (FCCs) in these Cu-doped QDs is probed via a combination of surface photovoltaic (SPV), photoacoustic (PA), and electric-field-induced SPV techniques, supplemented by the UV–VIS absorption spectrum and Raman spectrum. The results confirm that the two doping mechanisms result in different doping locations and microelectronic structures of the Cu-doped QDs. The distinctive microelectronic structure of the QDs prepared by nucleation doping, as compared with those prepared by growth doping, results in a number of favorable SPV characteristics. For example, the QDs prepared by nucleation doping exhibit a higher SPV response intensity at 600 nm because of a higher concentration of photogenerated FCCs. The ratio of the strongest SPV response and the strongest PA signal of the QDs prepared by nucleation doping is up to 2.41 times greater than those of the QDs prepared by growth doping. This is because the greater numbers of photogenerated FCCs in the QDs prepared by nucleation doping generate the PV effect rather than the PA effect that is caused by a nonradiative de-excitation process. The position of the shoulder peak of the SPV response at a long wavelength of the QDs prepared by nucleation doping is significantly red-shifted compared with that of the QDs prepared by growth doping, leading to a broader SPV response range in the visible region. The QDs prepared by nucleation doping have a more obvious donor feature than those prepared by growth doping.
关键词： photogenerated carriers,Cu-doped ZnSe/ZnS/L-Cys,quantum dots,photoacoustic,surface photovoltaic,nucleation doping,growth doping
更新于2025-09-11 14:15:04
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Noncontact photoacoustic angiography with an air-coupled ultrasonic transducer for evaluation of burn injury
摘要： In vivo identi?cation of viable and thermally coagulated blood in a burn wound can be used to pro?le the type, extent, and site of the burn, thus assisting the removal of necrotic tissue in preparation for skin grafts. Recently, intensive research on photoacoustic imaging (PAI) has been conducted to evaluate burn injury. However, most PAI systems usually take the approach of direct physical contact of an acoustic detector or an impedance matching medium with the vulnerable burned skin, which exposes signi?cant limitations on the diagnosis of burn injuries. Here, we present a noncontact PAI system, based on a custom designed air-coupled ultrasonic transducer, enabling in vivo noncontact vasculature to be imaged without contrast agents. Using the natural difference in light absorption between coagulated and non-coagulated blood at the wavelength of 532 nm, this PAI system possesses an immanent advantage to discriminate viable and thermally coagulated blood in burned tissues. Phantom experiments and burned rabbit’s skin imaging have been implemented to demonstrate that the noncontact PAI technique could be valuable in the adjuvant diagnosis and observation of burns.
关键词： air-coupled ultrasonic transducer,noncontact,photoacoustic imaging,burn injury,vasculature
更新于2025-09-11 14:15:04
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Biodegradable Bi <sub/>2</sub> O <sub/>2</sub> Se Quantum Dots for Photoacoustic Imaging-Guided Cancer Photothermal Therapy
摘要： As new 2D layered nanomaterials, Bi2O2Se nanoplates have unique semiconducting properties that can benefit biomedical applications. Herein, a facile top-down approach for the synthesis of Bi2O2Se quantum dots (QDs) in a solution is described. The Bi2O2Se QDs with a size of 3.8 nm and thickness of 1.9 nm exhibit a high photothermal conversion coefficient of 35.7% and good photothermal stability. In vitro and in vivo assessments demonstrate that the Bi2O2Se QDs possess excellent photoacoustic (PA) performance and photothermal therapy (PTT) efficiency. After systemic administration, the Bi2O2Se QDs accumulate passively in tumors enabling efficient PA imaging of the entire tumors to facilitate imaging-guided PTT without obvious toxicity. Furthermore, the Bi2O2Se QDs which exhibit degradability in aqueous media not only have sufficient stability during in vivo circulation to perform the designed therapeutic functions, but also can be discharged harmlessly from the body afterward. The results reveal the great potential of Bi2O2Se QDs as a biodegradable multifunctional agent in medical applications.
关键词： biodegradable,Bi2O2Se,2D layered materials,photothermal agents,photoacoustic imaging
更新于2025-09-11 14:15:04