Key Engineering Materials Vols. 364-366

Abstract: With the advent of the new complex optical system, alignment technology is necessary. In this paper, is presented an alignment algorithm whose main idea is composed of damped least square method and singular value decomposition method. In addition, the how and why to enter the damped factor into algorithm is explained. According to this algorithm, an alignment software package was compiled and compared self-compiled software with alignment package of CODE V. Results show that, this self-compiled software is much more valid than alignment package of CODE V. For a field of view of 2° R-C system, average MTF over the field of view was greater than 0.3 at 50 line pairs /mm.

Abstract: An efficient phosphorescent white organic light-emitting diode (WOLED) was realized by using a bright blue-emitting layer, iridium (III) bis [(4, 6-di-fluoropheny)-pyridinato-N, C2’] picolinate doped 4.4’-bis (9-carbazolyl)-2, 2’-dimethyl-biphenyl, together with tris (2- Phenylpyridine) iridium and bis (1-phenyl-isoquinoline) acetylacetonate iridium (III) were codoped into 4,4’-N,N’-dicarbazole-biphenyl layer to provide blue, green, and red emission for color mixing. The device emission color was controlled by varying dopant concentrations and the thickness of blue and green-red layers as well as tuning the thickness of exciton-blocking layer. The maximum luminance and power efficiency of the WOLED were 37100cd/m2 at 17 V and 7.37lm/W at 5V, respectively. The Commission Internationale de 1’Eclairage (CIE) chromaticity coordinate changes from (0.41, 0.42) to (0.37, 0.39) when the luminance rangeed from 1000cd/m2 to 30000cd/m2.

Abstract: Microscopy is an important tool in biology and medicine, but it is often limited to optical imaging structures with high numerical aperture(NA) with a short working distance(wd), for example NA = 0.6 and wd <1 mm are usual. The common microscope objective is inadequate for imaging of living cells in culture as an optical imaging structure with both high numerical aperture and long working distance is required. In this study, a novel optical design has been developed to meet the long working distance and high resolution power imaging of living cells in a vessel with a high culture solution thickness, where cells need to be developed in about 48 hours or a week. The developed optical design was characterized by an ultra-long working distance (wd >13.5 mm) and high numerical aperture (NA = 0.7). This optical imaging system is not only good for the subcellular imaging of free-floating cells in culture, but also for the imaging of cells attached at a surface of vessel.

Abstract: The aim of this work is to assess the cerebrovascular reserve capacity (CVRC) by MR PWI and photoacoustic brain imaging with “ACZ” tolerance test in mouse and rat, and to compare their role in evaluating the CVRC. Experimental animals included 2 groups: Wistar-Kyoto rats (WKY) (12-week-old, 235~265g) were assessed by MRI and BALB/c mice (4-week-old, 25~35g body weight) were assessed by our photoacoustic imaging system. On photoacoustic imaging, the diameter of the vascular in the superficial layer of the mouse cortex were measured and compared between the resting and acetazolamide (Acz)-activated mice, which reflected cerebral blood flow (CBF) without blood sampling. MR PWI was performed respectively before and after acetazolamide administrated orally on a clinical 1.5 Tesla GE Signa MR fx/i whole-body MR system. The region of interest (ROI) was chosen in the bilateral frontal lobe to measure the value of rCBV, rCBF and MTT. The results show that there was statistical difference between the resting and acetazolamide (Acz)-activated animals in the values of the diameter of the vascular in the superficial layer of the mouse cortex by photoacoustic imaging and in the values of rCBV and rCBF（P＞0.05）of the rat by MRI. It was concluded that the method of PWI and photoacoustic imaging combined with the “ACZ stress test” can be used to evaluate the CVRC by measuring values of rCBV and rCBF and diameter of the vascular, respectively.

Abstract: A novel nonlinear confocal microscopic imaging system based on Raman induced Kerr effect spectroscopy (RIKES) is presented in this paper. The three-dimensional (3-D) microscopic imaging theory is derived with the Fourier imaging theory and nonlinear optical principle. The impact of RIKES on the spatial resolution and imaging properties of confocal microscopic imaging system has been analyzed in detail by the imaging theory. It’s proved that the RIKES nonlinear microscopic imaging system can effectively improve the imaging contrast and provide more characteristic information on Raman spectrum and optical nonlinear Kerr effect, thus greatly improving the imaging quality of confocal microscopic imaging system. It’s shown that the spatial resolution of RIKES confocal microscopic imaging system is higher than that of two-photon confocal microscopic imaging system.

Abstract: Highly efficient and unusual structures white organic light-emitting devices were fabricated based on phosphorescence sensitized 5,6,11,12-tetraphenylnaphthacene. The device structure was ITO / NPB (30 nm)/CBP: 10% DPVBi (10 nm)/CBP (5 nm) /CBP:x% Ir(ppy)3 : y% rubrene (20 nm)/ CBP (5 nm)/ CBP: 10% DPVBi (10 nm)/BCP (10 nm)/ Alq3 (30 nm)/LiF(0.5 nm)/Al, where NPB is N,N '-bis- (1-naphthyl)- N,N ' –diphenyl -1, 1 '- biphenyl-4,4 '-diamine as a hole transporting layer, CBP 4,4,N,N’-dicarbazolebiphenyl as host,DPVBi is 4,4 '-bis(2,2 -diphenyl vinyl)-1,1 '-biphenyl as blue fluorescent dye，Rubrene is 5,6,11,12,-tetraphenylnaphthacene as fluorescent dye,Ir(ppy)3 is factris (2-phenylpyridine) iridium as phosphorescent sensitizer .BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline as hole-blocking layer, and Alq3 is tris(8- hydroxyquinoline) aluminum as an electron-transporting layer. In this device, phosphorescent emissive layer was sandwiched between two blue fluorescent doped ones. This architecture allowed for resonant energy transfer from both the host singlet and triplet energy levels that minimized exchange energy losses. Thus, a WOLED with a maximum luminous efficiency of 11.63 cd/A, a maximum power efficiency of 7.37 lm/W, a maximum luminance of 31770cd/m2, and Commission Internationale de L’Eclairage coordinates of (0.34.0.36) was achieved.

Abstract: Photoacoustic imaging (also called optoacoustic or thermoacoustic imaging) can image vascularity clearly with simultaneous high contrast and high spatial resolution, and has the potential to be an application for tumor diagnosis and treatment monitoring. In a unique photoacoustic system, a single pulse laser beam was used as the light source for both cancer treatment and for concurrently generating ultrasound signals for photoacoustic imaging. The photoacoustic system was used to detect early tumor on the rat back, and the vascular structure around the tumor could be imaged clearly with optimal contrast. This system was also used to monitoring damage of the vascular structures before, during and after photodynamic therapy of tumor. This work demonstrates that photoacoustic imaging can potentially be used to guide photodynamic therapy and other phototherapies using vascular changes during treatment. Prospective application of photoacoustic imaging is to characterize and monitor the accumulation of gold nanoshells in vivo to guide nanoshell-based thermal tumor therapy.

Abstract: Scanning photoacoustic tomography with a piezoelectric double-ring sensor was explored to image biological tissues, and short laser pulses irradiated tissues to generate acoustic waves by thermoelastic expansion. The laser-induced photoacoustic waves were detected by a piezoelectric double-ring sensor. This double-ring sensor has the advantage that it is more sensitive in the forward direction compared with other conventional sensors. An optical fiber for illumination of the sample was integrated with the sensor, which enabled reflection-mode detection of ultrasonic waves. Consequently, two-dimension photoacoustic tomography of biological tissues could be obtained in a manner analogous to the ultrasound B-scan mode by a linear scan over the tissue surfaces. To reach a large depth, 1064nm laser light was used in our experiments. The experimental results showed that the reconstructed photoacoustic images agree well with the structures of the samples. It demonstrated that this sensor has potential to monitoring tumor angiogenesis, and antiangiogenic therapy in vivo.

Abstract: Our recent work [1] theoretically revealed that speckles can be formed when nanofluids containing a modest volume fraction of nanoparticles are illuminated by a monochromatic laser beam. This paper focuses on the key issues, including the experimental setup, the particle volume fraction of the nanofluid, the flow velocity of the nanofluid and the diameter of the pipe, in measuring the velocities of nanoparticles in nanofluids with laser speckle velocimetry (LSV). First an experimental setup is established according to the optical characteristics of nanoparticle and the measuring principles of particle image velocimetry (PIV) and LSV. Then a conclusion is made from the experimental results that clear speckle patterns can be formed when the particle volume fraction is between 0.0005% and 0.002% is able to form. Finally, in order to make it applicable to utilize LSV to measure the velocities of nanoparticles in nanofluids that flow in pipe, nanofluids can not flow too fast and the diameter of the pipe should not be too small.

Abstract: The scanning laser line source (SLLS) technique is a novel laser-based inspection method for the ultrasonic detection of small surface-breaking defects. The SLLS approach is based on monitoring the change in laser generated ultrasound as a laser line source is scanning over a defect. It has provided enhanced signal-to-noise performance compared to the traditional pitch-catch or pulse-echo ultrasonic methods. In this paper, an experimental method is presented to detect surface acoustic waves (SAW) with polyvinylindene fluoride(PVDF) transducer. The ultrasonic signal is converted into electric signal by piezoelectricity of the PVDF, which is attached to a micro-knife edge clamped on a metal device. The SAW are excited by employing a pulsed Nd:YAG laser on aluminum plate with artificial surface-breaking defects. The laser line source is accurately shifted by the motorized translation stage, while the PVDF is located at a fixed position on the specimen. When the laser line source is scanning over the defect, the ultrasonic signals are monitored, meanwhile the characteristic changes in the amplitude and frequency content are observed. Consequently, the position of the defect can be determined by analyzing the obtained signals. The experimental system with high sensitivity provides a detection method of small surface-breaking defects on metal and gives convincing experimental evidence for the interaction mechanism between the SAW and the surface-breaking defects.