Three-dimensional femtosecond laser nanolithography of crystals

Nanostructuring hard optical crystals has so far been exclusively feasible at their surface, as stress induced crack formation and propagation has rendered high precision volume processes ineffective. We show that the inner chemical etching reactivity of a crystal can be enhanced at the nanoscale by more than five orders of magnitude by means of direct laser writing. The process allows to produce cm-scale arbitrary three-dimensional nanostructures with 100 nm feature sizes inside large crystals in absence of brittle fracture. To showcase the unique potential of the technique, we fabricate photonic structures such as sub-wavelength diffraction gratings and nanostructured optical waveguides capable of sustaining sub-wavelength propagating modes inside yttrium aluminum garnet crystals. This technique could enable the transfer of concepts from nanophotonics to the fields of solid state lasers and crystal optics.Comment: Submitted Manuscript and Supplementary Informatio

Comparison of Different Temperatures on Bending Properties of Six Niti Endodontic File Systems

Introduction: Manufacturers claim that modern NiTi files with proprietary heat treatment transform at higher temperatures, thus staying more martensite and being more resistant to cyclic fatigue and more flexible. There are some studies comparing the effect of body temperature and room temperature on cyclic fatigue of these newer NiTi files. However, there is not yet a study published for evaluating the relationship between bending properties of NiTi instruments and temperature following the ISO 3630-1 guideline. The objective of this study was to evaluate how temperature affects the bending properties of six different brands of NiTi rotary instruments with different transformation temperature ranges. Methods: Six commercially available NiTi files were selected for this experiment. The tested files included K3 40/.04 (Sybron Endo, Orange, CA), ProFile Series 29 Green Size 6 (Dentsply Tulsa Dental Specialties), K3XF 40/.04 (Sybron Endo, Orange, CA), Vortex Blue 40/.04 (Dentsply Tulsa Dental Specialties), ProFile Vortex 40/.04 (Dentsply Tulsa Dental Specialties), and HyFlex CM™ 40/.04 (Coltène/Whaledent Inc., Cuyahoga Falls, OH). The Austenite finish temperatures of the files were 9.6 ± 0.5, 17.6 ± 0.6, 24.9 ± 1.1, 35.4 ± 1.2, 45.7 ± 0.9, and 60.3 ± 3.1, respectively. The bending properties of the files were measured using a torsiometer (Sa bri Dental Enterprises, Inc. Downers Grove IL) following ISO 3630-1 guidelines. Twelve of each file type were grouped into 3 groups based on temperatures. Each temperature group had a total of 72 files. Group 1 measured the bending moment (g.cm) at 9±2°C, group 2 at 23±2°C, and group 3 at 35±2°C. The data was statistically analyzed by ANOVA and post hoc HSD (P\u3c0.05) Results: For all tested files, the bending moment of the files increased as the temperature rose from 9to 23 to 35°C. At all temperatures, HyFlex CM was significantly more flexible than other files. ProFile Vortex, K3XF, and Vortex Blue showed similar flexibility with each other. They were significantly more flexible than ProFile Series 29, which was significantly more flexible than K3. Conclusion: Testing temperature and brand of the files were significant independent variables affecting the flexibility of the files

Development of sputtered techniques for thrust chambers

Techniques and materials were developed and evaluated for the fabrication and coating of advanced, long life, regeneratively cooled thrust chambers. Materials were analyzed as fillers for sputter application of OFHC copper as a closeout layer to channeled inner structures; of the materials evaluated, aluminum was found to provide the highest bond strength and to be the most desirable for chamber fabrication. The structures and properties were investigated of thick sputtered OFHC copper, 0.15 Zr-Cu, Al2O3,-Cu, and SiC-Cu. Layered structures of OFHC copper and 0.15 Zr-Cu were investigated as means of improving chamber inner wall fatigue life. The evaluation of sputtered Ti-5Al-2.5Sn, NASA IIb-11, aluminum and Al2O3-Al alloys as high strength chamber outer jackets was performed. Techniques for refurbishing degraded thrust chambers with OFHC copper and coating thrust chambers with protective ZrO2 and graded ZrO2-copper thermal barrier coatings were developed

Full-Shell X-Ray Optics Development at NASA Marshall Space Flight Center

NASAs Marshall Space Flight Center (MSFC) maintains an active research program toward the development of high-resolution, lightweight, grazing-incidence x-ray optics to serve the needs of future x-ray astronomy missions such as Lynx. MSFC development efforts include both direct fabrication (diamond turning and deterministic computer-controlled polishing) of mirror shells and replication of mirror shells (from figured, polished mandrels). Both techniques produce full-circumference monolithic (primary + secondary) shells that share the advantages of inherent stability, ease of assembly, and low production cost. However, to achieve high-angular resolution, MSFC is exploring significant technology advances needed to control sources of figure error including fabrication- and coating-induced stresses and mounting-induced distortions

Polymer Matrix Nanocomposites by Inkjet Printing

This paper describes work on a continuing project to form functional composites that contain ceramic nanoparticles using a Solid Freeform Fabrication (SFF) inkjet printing method. The process involves inkjet deposition of monomer/particle suspensions in layers followed by curing each layer in sequence using UV radiation. The reactive monomer is hexanediol-diacrylate (HDODA); the polymer forming reaction proceeds by a free radical mechanism. The liquid monomer containing nanoparticles is essentially a printing ink formulation. Successfully suspending the particles in the monomer is critical. We have developed a surface treatment method for forming stable suspensions of the nanoparticles so that they remain discrete throughout the processing sequence. The SFF process involves careful control of the polymer cure so that the interface between layers is seamless and residual stresses in the composites are eliminated. An immediate use for such composites is in optical applications as gradient refractive index lenses (GRIN). GRIN lenses have planar surfaces, eliminating the need for costly grinding and polishing. The planar surfaces also eliminate optical aberrations that result at the edges of spherical lenses and diminish the accuracy of focus. If the appropriate nanoparticles are fully dispersed they will modify the polymer's refractive index without interfering with light transmission. The effect is additive with volume concentration. Using 'inks' of different compositions in a multiple nozzle inkjet printer allows the formation of composites with precise composition gradients. Since an object is built one planar layer at a time, changes can be made readily both within each layer and from layer to layer. Inkjet printing with picoliter resolution is ideal for this task. Working with SiC nanoparticles in HDODA as a model system for demonstrating the inkjet deposition process, nanocomposite films with a linear concentration gradient varying from 0 to 4.5% (wt) were fabricated on Silicon wafers. These composites are 30 layer films, which total 140µm in thickness. Each layer in the composite is about 5 µm in thickness. Analytical methods for characterizing the dispersion of the nanoparticles in the composite and some of the salient optical properties of the composites also were established. The status of the program is reviewed in this paper.Mechanical Engineerin

Template assisted surface micro microstructuring of flowable dental composites and its effect on the microbial adhesion properties

Despite their various advantages, such as good esthetic properties, absence of mercury and adhesive bonding to teeth, modern dental composites still have some drawbacks, e.g., a relatively high rate of secondary caries on teeth filled with composite materials. Recent research suggests that microstructured biomaterials surfaces may reduce microbial adhesion to materials due to unfavorable physical material–microbe interactions. The objectives of this study were, therefore, to test the hypotheses that (i) different surface microstructures can be created on composites by a novel straightforward approach potentially suitable for clinical application and (ii) that these surface structures have a statistically significant effect on microbial adhesion properties.Peer ReviewedPostprint (author's final draft

Copper Electrodeposition in Mesoscale Through-Silicon-Vias

Copper (Cu) electrodeposition (ECD) in through-silicon-vias (TSVs) is an essential technique required for high-density 3-D integration of complex semiconductor devices. The importance of Cu ECD in damascene interconnects has led to a natural development towards copper electrodeposition in TSVs. Cu ECD is preferred over alternative approaches like the chemical vapor deposition (CVD) of tungsten (W) or aluminum (Al) because Cu ECD films have lower film stress, lower processing temperatures, and more optimal thermal and electrical properties as compared with CVD W or Al. Via filling with electroplated Cu on substrates that have undergone atomic layer deposition of a conformal platinum seed metal is investigated herein. These mesoscale vias (600 μm depth, 5:1 aspect ratio) will be utilized in ultra-high-vacuum systems and thus require a uniform, void-free Cu deposit of sufficient thickness to prevent device degradation due to skin effects when RF frequencies as high as 100 V at 100 MHz are used. Conformally Cu-lined TSVs are achieved through the implementation of a complex ECD parameter scheme, and these results are compared with computational finite element modeling (FEM) outcomes. A novel, single additive chemistry is also developed and implemented to achieve fully filled void-free mesoscale TSVs within 6 hours of plating time, which represents an extraordinarily fast and controllable plating rate (100 μm/hour) for interconnect (IC) feature filling