Additive Manufacturing and Applications of Silica Glass Materials

The difficulty in shaping and fabrication of miniaturized features on glass structures using conventional fabrication techniques makes the recent advancements in glass manufacturing necessary. Pioneer efforts towards glass additive manufacturing have proven to be the nexus between the past and the future of glass fabrication. Additive manufacturing potentially allows for speed, scalability, environmental and cost friendliness, high resolution as well as flexibility for functional glass materials. Adapting additive manufacturing methods toward glass fabrication is thus of great importance. We first fabricated three dimensional doped and undoped Borosilicate glasses via stereolithography which exhibited comparable optical properties to commercial glasses, irrespective of their low softening temperatures. Processing parameters of densification and calcination were optimized to achieve structural and optical stability of the resulting undoped and Cerium-doped borosilicate glass. Optical parameters including the optical band gap, Urbach energy and refractive index were deduced from the optical absorption spectra with comparable quality to doped glasses fabricated by other methods. vii The glasses exhibited a band gap of 3 eV, Urbach energy of 0.75 eV and refractive index of 2.14 for 8% Ce-doped glass, respectively. The results indicate the suitability of Ceriumdoped glass fabricated by stereolithography for luminescence applications and that additive manufacturing could be promising for borosilicate glass fabrication. We also investigated the use of the stereolithography technique for fabrication of functionally graded materials with emphasis on gradient refractive index optics. These class of materials allow for planar surfaces which make mounting in complex optical systems much easier in addition to providing enhanced optical properties. They find applications in facets such as micro-optical telescopes, solid state lasers, fiber collimators, optical data storage etc. Stereolithography is a good technique for gradient refractive index optics because it allows for a flexibility of dopant inculcation so that there is a variation in the refractive within the glass structure. Our simulation results for the gradient optical lens designs based on the adoption of the precursor cum resin sludge properties showed measurable and tunable optical properties such as spherical aberrations. Experimental results establish stereolithography as a veritable technique and show the propensity for the adaptation of this technique for the fabrication process

Development of high performance hybrid capacitors

Event: SPIE Defense + Commercial Sensing, 2019, Baltimore, Maryland, United StatesThe article of record as published may be found at http://dx.doi.org/10.1117/12.2520249Electrochemical capacitors are viable energy storage solution but their low energy density restricts their widespread deployment in many electronic devices. The motivation behind hybrid capacitor is the desire to improve the energy density output of electrochemical capacitors by combining electrodes capable of storing charges by surface adsorption with redox active electrodes. The overall performance output of the energy storage device are governed by the intrinsic characteristics of electrodes employed and their preparation techniques. In this paper, we discuss different hybrid capacitor devices employing binder-free electrodes based on electrostatic spray deposition or electrophoretic deposition techniques.This work was partially supported by the National Science Foundation (NSF) projects (no. 1506640,no. 1509735 and no. 1611088) and Nanosystems Engineering Research Center (NERC) for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) center seed funding.This work was partially supported by the National Science Foundation (NSF) projects (no. 1506640,no. 1509735 and no. 1611088) and Nanosystems Engineering Research Center (NERC) for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST) center seed funding

Determining nanoform similarity via assessment of surface reactivity by abiotic and in vitro assays

Grouping of substances is a method used to streamline hazard and risk assessment. Assessment of similarity provides the scientific evidence needed for formation of groups. This work reports on justification of grouping of nanoforms (NFs) via similarity of their surface reactivity. Four reactivity assays were used for concentration dependent detection of reactive oxygen species (ROS) generated by NFs: abiotic assays FRAS, EPR and DCFH2-DA, as well as the in vitro assay of NRF2/ARE responsive luciferase reporter activation in the HEK293 cell line. Representative materials (CuO, Mn2O3, BaSO4, CeO2 and ZnO) and three case studies of each several NFs of iron oxides, Diketopyrrolopyrroles (DPP)-based organic pigments and silicas were assessed. A novel similarity assessment algorithm was applied to quantify similarities between pairs of NFs, in a four-step workflow on concentration-response curves, individual concentration and response ranges, and finally the representative materials. We found this algorithm to be applicable to all abiotic and in vitro assays that were tested. Justification of grouping must include the increased potency of smaller particles via the scaling of effects with specific surface, and hence quantitative similarity analysis was performed on concentration-response in mass-metrics. CuO and BaSO4 were the most and least reactive representative materials respectively, and all assays found BaSO4/CuO not similar, as confirmed by their different NOAECs of in vivo studies. However, similarity outcomes from different reactivity assays were not always in agreement, highlighting the need to generate data by one assay for the representative materials and the candidate group of NFs. Despite low similarity scores in vitro some pairs of case study NFs can be accepted as sufficiently similar because the in vivo NOAECs are similar, highlighting the conservative assessment by the abiotic assays