Microfabrication and characterization of teflon AF-coated liquid core waveguide channels in silicon

The fabrication and testing of Teflon AF-coated channels on silicon and bonding of the same to a similarly coated glass wafer are described. With water or aqueous solutions in such channels, the channels exhibit much better light conduction ability than similar uncoated channels. Although the loss is greater than extruded Teflon AF tubes, light throughput is far superior to channels described in the literature consisting of [110] planes in silicon with 45/spl deg/ sidewalls. Absorbance noise levels under actual flow conditions using an LED source, an inexpensive photodiode and a simple operational amplifier circuitry was 1/spl times/ 10/sup -4/ absorbance units over a 10-mm path length (channel 0.17-mm deep /spl times/0.49-mm wide), comparable to many commercially available macroscale flow-through absorbance detectors. Adherence to Beer's law was tested over a 50-fold concentration range of an injected dye, with the linear r/sup 2/ relating the concentration to the observed absorbance being 0.9993. Fluorescence detection was tested with fluorescein as the test solute, a high brightness blue LED as the excitation source and an inexpensive miniature PMT. The concentration detection limit was 3 /spl times/ 10/sup -9/ M and the corresponding mass detection limit was estimated to be 5 /spl times/ 10 /sup -16/ mol.     

Luminescence detection with a liquid core waveguide

A new fluoropolymer tube is proposed as the basis of a novel class of liquid core waveguide-based luminescence detectors. Both chemiluminescence and photoluminescence detectors are possible. In the latter case, illumination is transverse to the main axis of the tube. With such a geometry, it is even possible to operate without monochromators, although limits of detection do improve with the incorporation of monochromators. The nature of the design is such that it is particularly simple to fabricate detectors in a flow-through configuration and where the light from the cell is coupled to a photodetector by an optical fiber. No focusing optics are necessary. A number of applications are illustrated. Attainable limits (LODs, S/N = 3) of detection include 150 pM fluorescein with a 254-nm excitation source, 200 amol of fluorescein in a capillary electrophoresis setup with excitation by two blue light-emitting diodes, 35 nM NH(3) as the isoindole derivative in a flow injection analysis system using a photodiode detector, 50 nM methylene blue and 1 nM Rhodamine 560 using respectively red and green LED arrays and an avalanche photodiode and a PMT in a FIA configuration, 100 parts per trillion by volume gaseous formaldehyde as the Hantzsch reaction product with cyclohexanedione using a diffusion scrubber, 2.7 μM and 17 nM hypochlorite based on its chemiluminescence reaction with luminol with photodiode and PMT detectors, respectively, and 1 ppm SO(4)(2)(-) based on nephelometric detection at 470 nm. The approach described herein leads to particularly simple and inexpensive luminescence detectors with excellent sensitivity.     

Direct Electron-Beam Patterning of Teflon AF

Teflon AF thin films have been directly patterned by electron-beam lithography without the need for chemical development. The pattern depth was found to be linearly related to exposure dose and increases with increasing film thickness. Features as small as 200 nm have been resolved. Fourier transform infrared measurements indicate that the electron-beam-induced patterning is related to degradation of the fluorinated dioxole group present in amorphous Teflon.      

Fabrication of PDMS-Based Nitrite Sensors Using Teflon AF Coating Microchannels

This study shows a novel polydimethylsiloxane (PDMS) nitrite sensor using liquid-core waveguide techniques. A 6 cm straight and Teflon AF 1601S coated PDMS microchannel (600 mum width and depth) replicated from a SU-8 master and sealed with a glass slide with the same coating. This formed a low index of refraction channel in which a high index aqueous solution was flowed. Light generated by a fiber-coupled tungsten halogen lamp propagated by total internal reflection to the end of the channel where the light was detected using a palm-size CCD array spectrometer. The result shows a dramatic difference between channels with and without a Teflon coating. The absorbance response of this sensor varies linearly with concentration and adheres to Beer's law. Moreover, calculations of absorbance using this sensor are in excellent agreement with a commercial spectrometer. This innovative technique provides a potentially low-cost and high efficient approach to fill the inspection technology gap between in situ and laboratory analyses. It is believed that the novel PDMS-based nitrite sensor is expected to give an impact to the aqueous inspection and to create a highly value-added technology in optical test and measurement industry.     

Capillary isoelectric focusing of proteins with liquid core waveguide laser-induced fluorescence whole column imaging detection

A capillary isoelectric focusing (CIEF) system with liquid core waveguide (LCW) laser-induced fluorescence whole column imaging detection was developed in this study. A Teflon AF 2400 capillary was used as both the separation channel and the axially illuminated LCW. The excitation light was introduced at one end of the capillary, and propagated forward within the capillary. As the Teflon AF 2400 capillary has a refractive index (n = 1.29-1.31) lower than that of water (n = 1.33), total internal reflection was very apparent The employment of the Teflon AF 2400 capillary avoided the use of high refractive index additives such as glycerol, accommodating the system to wider applications. Due to its inert chemical properties, the capillary exhibited limited protein adsorption and electroosmotic flow; thus, the need for capillary preconditioning with polymeric solution and the addition of polymeric additives into the sample mixture can be avoided. Three types of proteins, naturally fluorescent proteins, covalently labeled proteins, and noncovalently labeled proteins, were examined using this method. CIEF under denaturing conditions was also explored, and several advantages over the native mode were found. When compared to a commercially available instrument with UV detection, the separation efficiency and peak capacity were similar while the detection sensitivity was enhanced by 3-5 orders of magnitude.     

Thermal conductivity of amorphous Teflon (AF 1600) at high pressure

The thermal conductivity, λ of amorphous Teflon AF 1600 [poly(1,3-dioxole-4,5-difluoro-2,2-bis(trifluoromethyl)-co-tetrafluoroethylene)] has been measured at pressures up to 2 GPa in the temperature range 93–392 K. At 295 K and atmospheric pressure, we obtained λ=0.116, W·m⁻¹·K⁻¹. The bulk modulus was measured up to 1.0 GPa in the temperature range 150–296 K and the combined data yielded the following values ofg=(∂ln λ ∂lnp) _r :2.8±0.2 at 296 K, 3.0±0.2 at 258 K, 3.0±0.2 at 236 K. 3.4±0.2 at 200 K. and 3.4±0.2 at 150 K.     

Thermal characterization of liquid core optical ring resonator sensors

The liquid core optical ring resonator (LCORR) has recently shown promise as a high-sensitivity label-free lab-on-a-chip biological-chemical sensor. We investigate experimentally and theoretically the temperature dependence of the LCORR to establish a noise baseline, which will enable us to implement a temperature stabilization mechanism to reduce the thermally induced noise and to improve the sensor detection limit. Our studies involve analysis of the thermo-optic and thermomechanical effects of fused silica and aluminosilicate glass as they impact LCORR performance. Both thick-walled and thin-walled LCORRs are investigated to elucidate the contribution of water in the core to the thermal response of the LCORRs. Theoretical calculations based on Mie theory are used to verify the experimental observations.     

Fabrication and characterization of a third-order nonlinear organic-polymer composite glass waveguide: a self-phase modulator

Composite organic-polymer glass optical waveguides in which coupling to the nonlinear organic-polymer layers was achieved by excitement of the underlying ion-exchanged glass waveguide and coupling of the light to the organic-polymer layer were fabricated and measured. A picosecond pulsed color center laser (λ = 1.5 μm) was used to measure the third-order optical susceptibility χ((3))(-w; w, -w, w) in an organic-dye-polymer composite glass waveguide with a Mach-Zehnder interferometer. For a squaryliumdye-doped poly(methyl methacrylate)-styrene-acrylonitrile matrix polymer layer, a composite χ((3)) of roughly 90, in units of (χLiNbO)(3)((3)), was measured.     

Bioabsorbable polymer plates coated with bioactive glass spheres

In order to provide bioabsorbable self-reinforced poly (L/DL) lactide (P(L/DL)LA) 70 : 30 plates with osteoconductive bioactivity, spheres (125–250 µm) of a bioactive glass 13–93 were implanted onto a polymer plate preform by pressing. With appropriate pressing parameters glass spheres were firmly attached onto the polymer plate. The top of the glass spheres remained exposed. The bioactivity of the coated plates was examined in vitro with immersion in phosphate-buffered saline (PBS). Apatite was observed to precipitate on exposed glass sphere surfaces and the whole polymer surface within the first three days. © 1999 Kluwer Academic Publishers     

Synthesis and characterization of hollow glass microspheres coated by SnO2 nanoparticles

The composite of hollow glass microspheres coated by SnO₂ nanoparticles has been successfully fabricated via sol-gel method. The phase structures, morphologies, particle size, shell thickness, chemical compositions of the composite have been characterized by XRD, FESEM, and EDX. The results show that SnO₂ coating on hollow glass microspheres can be achieved, and the coating layers are constituted by SnO₂ nanoparticles of mean size ca. 15 nm. The SnO₂ coating layers grow thicker with the increased concentration of SnCl₄. The effects of parameters (reaction temperature, concentration of NaOH and SnCl₄, and time) were investigated to yield SnO₂ coating on hollow glass microspheres, and the UV-vis absorption spectra of the composites were studied.     

Bioactivity of degradable polymer sutures coated with bioactive glass

Novel bioactive materials have been prepared by coating violet resorbable Vicryl sutures with a bioactive glass powder derived from a co-precipitation method. Two techniques have been chosen for the composite preparation: pressing the sutures in a bed of glass powder and slurry-dipping of sutures in liquid suspensions of bioactive glass powders. The uniformity and thickness of the coatings obtained by the two methods were compared. The bioactivity of the sutures with and without bioactive glass coating was tested by soaking in an inorganic acellular simulated body fluid (SBF). The composite sutures were characterised by XRD, SEM and FTIR analyses before and after soaking in SBF solution to assess the formation of hydroxyapatite on their surfaces, which is a qualitative measure of their bioactivity. The possible use of bioactive sutures to produce tissue engineering scaffolds and as reinforcement of resorbable calcium phosphates is discussed.     

低辐射隔热复合镀膜玻璃的制备

采用溶胶-凝胶法成功制备了SnO2∶F/SiO2气凝胶复合镀膜玻璃,并采用扫描电子显微镜(SEM)、导热系数仪、红外光谱仪,紫外-可见光谱仪等对镀膜玻璃的微观结构、热导率、辐射率、透光率等进行了表征。结果表明,镀膜玻璃的透过率最高在75%左右;辐射率为0.53,复合镀膜玻璃与FTO玻璃相比,其热导率从3.615W/(m·K)降低到3.368W/(m·K),所得复合镀膜玻璃兼具低热导性和低辐射性。     

Mechanical properties of biodegradable polymer sutures coated with bioactive glass

Combining commercially available Polyglactin 910 (Vicryl®) sutures with bioactive glass powder offers new possibilities for application of composite materials in tissue engineering. Commercial bioactive glass (45S5 Bioglass®) powder was used to coat Vicryl® sutures and the tensile strength of the sutures was tested before and after immersion in simulated body fluid (SBF) as a means to assess the effect of the bioactive glass coating on suture degradation. Different gauge lengths (126.6 and 111.6 mm) and strain rates (2.54, 11.4 and 25.4 mm/min) were tested. The tensile strength of composite sutures was slightly lower than that of as-received Vicryl® sutures (404 MPa versus 463 MPa). However after 28 days immersion in SBF the residual tensile strength of the coated sutures was significantly higher, indicating a protective function of the Bioglass® coating. The tensile strength results were similar for the different gauge lengths and strain rates investigated. A qualitative explanation for the effect of bioactive glass coating on polymer degradation is offered.     

Microfabrication and characterization of spray-coated single-wall carbon nanotube film strain gauges

We present the design, fabrication, and characterization results of single-wall carbon nanotube (SWCNT) film strain gauges for potential applications as highly sensitive strain, weight, or pressure sensors on the macro-scale. A batch microfabrication process was developed for practical device construction and packaging using spray-coated SWCNTs and a conventional semiconductor process. The prototype was characterized using a commercial metal foil gauge with tensile and compressive testing on a binocular load cell. Our test results demonstrated that the proposed SWCNT film gauges have a linear relationship between resistance changes and externally applied strain. The gauge factor ranged from 7.0 to 16.4 for four different micro-grid configurations, indicating that the maximum strain sensitivity of the prototype was approximately eight times greater than that of commercial gauges.     

锶铁氧体包覆碳纳米管吸波材料的制备及表征

采用溶胶-凝胶法制备锶铁氧体包覆碳纳米管(CNTs)的吸波材料,并考察了碳纳米管含量对包覆后样品磁性能及吸波性能的影响.经TEM、XRD验证锶铁氧体成功地包覆在碳纳米管表面;ALVSM图中可以看出6%CNTs-SrFe11.5O19的磁性能最佳,矫顽力(Hc)为5916.13Oe.而经网络分析仪测定,5% CNTs-S...     

Infrared waveguide fabrications with an E-beam evaporated chalcogenide glass film

Chalcogenide glasses have a variety of unique optical properties due to the intrinsic structural flexibility and bonds metastability. They are desirable materials for many applications, such as infrared communication sensors, holographic grating, optical imaging, and ultrafast nonlinear optic devices. Here, we introduce a novel electron-beam evaporation process to deposit the good quality arsenic trisulfide (As₂S₃) films and then the As₂S₃ films were used to fabricate the As₂S₃ waveguides with three approaches. The first method is photoresist lift-off. Because of the restriction of thermal budget of photoresist, the As₂S₃ film must be deposited at the room temperature. The second one is the silicon dioxide lift-off process on sapphire substrates, in which the As₂S₃ film could be evaporated at a high temperature (>180 °C) for better film quality. The third one is the plasma etching process with a metal protective thin layer in the pattern development process.     

彩色双层复合镀膜玻璃的在线制备与性能

分别采用电化学方法和化学气相沉积法对生产线锡槽和退火窑内的浮法玻璃两次镀膜,制备出具有阳光控制功能的双层彩色浮法玻璃,采用分光光度计、扫描电镜、能谱仪、透射电镜、原子力显微镜和二次离子质谱等方法分析了复合镀膜样品的形貌．结构,研究了不同深度的膜层成分和性能．结果表明,可见光透射比与硅烷浓度和电流强度之间有强烈依赖性;上层的硅膜表面均匀平整,表面粗糙度约9．66nm,团粒尺寸约100nm,其厚度约70-78nm,且沿厚度方向呈梯度化氧化;底层膜中铜和铋的扩散深度约10μm．     

A fluxgate magnetometer with a metallic glass core

A square-wave excited pulse-height fluxgate circuit is described, using a metallic glass core fluxgate and a minimum amount of active components. High reliability and linearity have been achieved.