11 research outputs found

    Direct Ink Writing of Functional Fiber Composites

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    Fiber-polymer composites, consisting of the polymer matrix and functional synthetic/natural fibers, show tremendous promise due to their unique mechanical, thermal, and electrical properties. By printing such fiber-polymer composites using additive manufacturing (AM) techniques, the three-dimensional models can be fabricated with arbitrary free-form geometry and various functionalities. Direct ink writing (DIW) is an extrusion-based AM approach and has a diverse choice of printable matrix materials. Applications, including energy storage, mechanical reinforcements, and biomimetic materials, have been presented through DIW of fiber composites. Yet grand challenges such as the complicated process planning, low geometrical accuracy, filament shape instabilities, and minimal fiber extrusion capability still exist in the DIW of fiber-polymer composites. This dissertation aims to address these challenges in DIW of fiber-polymer composites and to develop a fundamental understanding of the complex interplay of ink properties, DIW printing process, and printed composite functionalities through testing the following hypotheses: Hypothesis I: The incorporation of an electric field between the printing nozzle and the substrate can induce an electrowetting effect to enlarge the printable ranges of materials and the working range of manufacturing process settings. Hypothesis II: The addition of water-washable gel can change the rheological properties of the fiber suspensions in a way that the shear-yielding and shear-thinning properties are enhanced to increase the printability of composites with higher geometrical accuracy. Hypothesis III: Sonication can remove the primary wall of natural fibers and enhances the printability of natural fibers in DIW while retaining its mechanical characteristics in the printed composite. The findings are beneficial to material science and manufacturing process, enabling significant improvements in DIW of fiber-polymer composites and future applications in functional devices fabrication in the following perspectives: a) Generalized mappings between the printed feature geometries and process parameters were developed. b) The influence of liquid ink rheological properties on printing stability was understood. c) Approaches for modifying synthetic/natural fiber for higher printability were established. d) Electric-field-assisted and temperature-controlled DIW process planning strategies were developed and evaluated. e) Novel applications of DIW printed fiber composites were demonstrated

    Patient characteristics.

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    <p>Patient characteristics.</p

    Estimated continuous annual BCSM rates and hazard ratio of BCSM in certain subpopulations.

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    <p>(A) Patients were age<40 with ER negative and node positive diseases. (B) Patients were age≥60 with ER positive and node negative diseases.</p

    Filtration process.

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    <p>We identified 228209 female patients (20 and 84 yrs) diagnosed stages I to III unilateral invasive breast cancer between January 1, 1990, and December 31, 2005, through Surveillance, Epidemiology, and End Results (SEER) Program (<a href="http://www.seer.cancer.gov/" target="_blank">www.seer.cancer.gov</a>) SEER*Stat Database: Incidence—SEER 18 Regs Research Data released April 2015, based on the November 2014 submission.</p

    Estimated continuous annual BCSM rates and hazard ratio of BCSM.

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    <p>A, B & C show estimated continuous annual BCSM rates. The solid line represents patients in cohort 1; the dashed line represents patients in cohort 2.D, E & F show differences of BCSM between patients in the two cohorts. Patients in C1 as reference, the absolute number of decreased BCSM rate (C2 minus C1).G, H & I show hazard ratio of BCSM (Cohort 1 versus cohort 2). Light grey shadows represent 95% CI of survival. HRs with 95% CIs were estimated from the flexible parametric survival models. Curves cut off at 0.5 yrs from diagnosis because of sparse data. Total population: A, D & G; ER negative: B, E & H; ER positive: C, F & I. Notes: Rates were reported per 1000 persons per year; y-axis scales were different in different analyses.</p

    Annual BCSM rates and hazard ratio of BCSM in the total population and different subgroups.

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    <p>Annual BCSM rates and hazard ratio of BCSM in the total population and different subgroups.</p

    Fully Packaged Carbon Nanotube Supercapacitors by Direct Ink Writing on Flexible Substrates

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    The ability to print fully packaged integrated energy storage components (e.g., supercapacitors) is of critical importance for practical applications of printed electronics. Due to the limited variety of printable materials, most studies on printed supercapacitors focus on printing the electrode materials but rarely the full-packaged cell. This work presents for the first time the printing of a fully packaged single-wall carbon nanotube-based supercapacitor with direct ink writing (DIW) technology. Enabled by the developed ink formula, DIW setup, and cell architecture, the whole printing process is mask free, transfer free, and alignment free with precise and repeatable control on the spatial distribution of all constituent materials. Studies on cell design show that a wider electrode pattern and narrower gap distance between electrodes lead to higher specific capacitance. The as-printed fully packaged supercapacitors have energy and power performances that are among the best in recently reported planar carbon-based supercapacitors that are only partially printed or nonprinted

    Two-Photon Polymerization of Butterfly Wing Scale Inspired Surfaces with Anisotropic Wettability

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    Wings of Morph aega butterflies are natural surfaces that exhibit anisotropic liquid wettability. The direction-dependent arrangement of the wing scales creates orientation-turnable microstructures with two distinct contact modes for liquid droplets. Enabled by recent developments in additive manufacturing, such natural surface designs coupled with hydrophobicity play a crucial role in applications such as self-cleaning, anti-icing, and fluidic manipulation. However, the interplay among resolution, architecture, and performance of bioinspired structures is barely achieved. Herein, inspired by the wing scales of the Morpho aega butterfly, full-scale synthetic surfaces with anisotropic wettability fabricated by two-photon polymerization are reported. The quality of the artificial butterfly scale is improved by optimizing the laser scanning strategy and the objective lens movement path. The corresponding contact angles of water on the fabricated architecture with various design parameters are measured, and the anisotropic fluidic wettability is investigated. Results demonstrate that tuning the geometrical parameters and spatial arrangement of the artificial wing scales enables anisotropic behaviors of the droplet’s motion. The measured results also indicate a reverse phenomenon of the fabricated surfaces in contrast to their natural counterparts, possibly attributed to the significant difference in equilibrium wettability between the fabricated microstructures and the natural Morpho aega surface. These findings are utilized to design next-generation fluid-controllable interfaces for manipulating liquid mobility on synthetic surfaces

    Intra-arterial chemotherapy (IAC) as primary therapy for infants less than 3 months of age.

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    <p>A&B: 6.9-week-old boy with unilateral sporadic retinoblastoma in right eye (Group D). A, Fundus photographs at initial examination (6.9-week-old). Right eye: large tumor with retinal detachment. B, Fundus photographs after 2 cycles of intra-arterial chemotherapy. After 2 cycles of IAC, complete tumor regression was achieved. C&D: 6.6-week-old boy with unilateral sporadic retinoblastoma in left eye (Group D). C, Fundus photographs at initial examination (6.6-week-old). Left eye: large tumor with retinal detachment. D, Fundus photographs after 3 cycles of intra-arterial chemotherapy. The tumor has shrunk and highly calcified. E&F: 11.3-week-old girl with unilateral sporadic retinoblastoma in right eye (Group D). E, Fundus photographs at initial examination (11.3-week-old). Right eye: large tumor with retinal detachment. F, Fundus photographs after 3 cycles of intra-arterial chemotherapy. The tumor has shrunk and highly calcified.</p
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