International network of cancer genome projects.

The International Cancer Genome Consortium (ICGC) was launched to coordinate large-scale cancer genome studies in tumours from 50 different cancer types and/or subtypes that are of clinical and societal importance across the globe. Systematic studies of more than 25,000 cancer genomes at the genomic, epigenomic and transcriptomic levels will reveal the repertoire of oncogenic mutations, uncover traces of the mutagenic influences, define clinically relevant subtypes for prognosis and therapeutic management, and enable the development of new cancer therapies.

Process of Pure Copper Fabricated by Selective Laser Melting (SLM) Technology under Moderate Laser Power with Re-Melting Strategy.

Pure copper (Cu) material, because of its high thermal conductivity, can be 3D printed to fabricate effective thermal management components. However, in the selective laser melting (SLM) process, due to copper's high optical reflectivity, Cu-based parts need to be printed using high laser power. In this study, we demonstrated 3D printing with a re-melting strategy is able to fabricate high-density and low-surface-roughness pure copper parts using only a moderate laser (350 W) power. The effect of the re-scan to initial scan speed ratio on the printing quality resulting from the re-melting strategy is discussed. The re-melting strategy is likened to a localized annealing process that promotes the recrystallization of the newly formed copper microstructures on the re-scan path. Given a hatch spacing of 0.06 mm and a powder layer thickness of 0.05 mm, Cu samples with 93.8% density and low surface roughness (Sa~22.9 µm) were produced using an optimized scan speed of 200 mm/s and a re-scanning speed of 400 mm/s, with a laser power of 350 W. Our work provides an approach to optimize the laser power for printing pure copper 3D parts with high relative density (low porosity) and low surface roughness while ensuring the lifetime stability of the part. The re-melting strategies have broad implications in 3D printing and are particularly relevant for metals with high reflectivity, such as pure copper.

Realization of Multifunctional Metamaterial Structure Based on the Combination of Vanadium Dioxide and Graphene.

Combining tunable properties and various functionalities into a single metamaterial structure has become a novel research hotspot and can be used to tackle great challenges. The multifunctional metamaterial structure that combines absorption, linear-to-circular (LTC) polarization conversion, filtering and switching functions into a single metamaterial device was designed and investigated in this study. The switching of different functions can be achieved based on the phase transition of vanadium dioxide (VO2) and change of graphene chemical potential. When VO2 is in a metal state, the multi-frequency absorption and LTC polarization conversion can be achieved with different chemical potentials. When VO2 is in the insulator state and the polarization angle of incident wave is 45°, the device can be used to select or isolate the incident waves with different polarization states in the frequency region of 1.2-1.8 THz. Furthermore, when the chemical potentials are 0.05 eV and 1.2 eV, the corresponding transmissions of the TE-polarized wave demonstrate the opposite results, realizing the switching functions in the frequency region of 0.88-1.34 THz. In the frequency region above 2 THz, the multi-frequency rejection filter can be achieved. The designed switchable multifunctional metamaterial device can be widely implemented in radar monitoring and communication systems.

The Effect of Geometric Parameters on Flow and Heat Transfer Characteristics of a Double-Layer Microchannel Heat Sink for High-Power Diode Laser.

The effect of the geometric parameters on the flow and heat transfer characteristics of a double-layer U-shape microchannel heat sink (DL-MCHS) for a high-power diode laser was investigated in this work. FLUENT 19.2 based on the finite volume method was employed to analyze the flow and heat transfer performance of DL-MCHS. A single variable approach was used to fully research the impact of different parameters (the number of channels, the channel cross-sectional shape, and the aspect ratio) on the temperature distribution, pressure drop, and thermal resistance of the DL-MCHS. The rectangular DL-MCHS heat transfer performance and pressure drop significantly increased with the rise in the channel's aspect ratio due to there being a larger wet perimeter and convective heat transfer area. By comparing the thermal resistance of the DL-MCHS at the same power consumption, it was found that the rectangular DL-MCHS with an aspect ratio in the range of 5.1180-6.389 had the best overall performance. With the same cross-sectional area and hydraulic diameter (AC = 0.36 mm, Dh = 0.417 mm), the thermal resistance of the trapezoidal microchannel heat sink was 32.14% and 42.42% lower than that of the triangular and rectangular ones, respectively, under the condition that the pumping power (Wpp) was 0.2 W. Additionally, the thermal resistance was reduced with the increment of the number of channels inside the DL-MCHS, but this would induce an increased pressure drop. Thus, the channel number has an optimal range, which is between 50 and 80 for the heat sinks in this study. Our study served as a simulation foundation for the semiconductor laser double-layer U-shaped MCHS optimization method using geometric parameters.

Plasmonically Enhanced Colloidal Quantum Dot/Graphene Doped Polymer Random Lasers.

An improvement in random lasers based on a colloidal quantum dot (QD)/graphene-doped polymer was observed and attributed to multiple light-scattering and graphene surface plasmon resonance. The emission characteristics of quantum dots doped with graphene oxide and reduced graphene oxide were compared. The QD/reduced graphene oxide hybrid exhibited a lower laser emission threshold (~460 µJ/cm2). The emission modes and thresholds were strongly dependent on both the graphene doping concentration and the external temperature. Decreased plasmon coupling was the primary reason for lower QD/graphene laser emission with increasing temperature. The optimum reduced graphene oxide concentration was 0.2 wt.%. This work provides a practical approach to optimizing the threshold and stability of random laser devices, with potential applications in displays, sensors, and anti-counterfeiting labels.

A facile chemical approach for preparing a SERS active silver substrate.

This communication describes a new surface-enhanced Raman scattering (SERS) active silver substrate prepared by iodination of the evaporated silver foil. After iodination, the morphology of the silver substrate undergoes a self-evolution process in which it displays accordingly the UV-vis absorption shift as well as the AFM topological test. Rhodamine 6G (R6G) is used as the probe molecule to evaluate the enhancement efficiency of the silver substrate at different self-evolution time intervals. The SERS intensity of R6G increases up to ∼29-fold and reaches a maximum after the substrate evolved for 24 h. This method is feasible for the production of an efficient SERS silver substrate.

Flow dependence of interfacial thermal resistance in nanochannels.

In nanochannel flows, the thermal resistance at the fluid-solid interface may depend on the flow scenario. In this work, we study the interfacial thermal resistance R(th) in nanoscale force-driven flows at different temperatures and fluid-wall interactions. For Ar flows in Cu and Ag channels, the fluid-wall binding energy is strong and it is found that R(th) assumes a maximum value as the external force is varied. The maximum value is caused by the fluid adsorption on the solid surfaces and the temperature increase in the fluid due to viscous frictions. However, when the fluid-wall interaction is weak, the maximum value is not observed and the interfacial thermal resistance decreases monotonously with increasing external force. With the presence of fluid adsorption, it is also found that the peak in R(th) is more detectable at low temperature than high temperature.

Flexible frequency selective metamaterials for microwave applications.

Metamaterials have attracted more and more research attentions recently. Metamaterials for electromagnetic applications consist of sub-wavelength structures designed to exhibit particular responses to an incident EM (electromagnetic) wave. Traditional EM (electromagnetic) metamaterial is constructed from thick and rigid structures, with the form-factor suitable for applications only in higher frequencies (above GHz) in microwave band. In this paper, we developed a thin and flexible metamaterial structure with small-scale unit cell that gives EM metamaterials far greater flexibility in numerous applications. By incorporating ferrite materials, the thickness and size of the unit cell of metamaterials have been effectively scaled down. The design, mechanism and development of flexible ferrite loaded metamaterials for microwave applications is described, with simulation as well as measurements. Experiments show that the ferrite film with permeability of 10 could reduce the resonant frequency. The thickness of the final metamaterials is only 0.3mm. This type of ferrite loaded metamaterials offers opportunities for various sub-GHz microwave applications, such as cloaks, absorbers, and frequency selective surfaces.

Stretchable conductive elastomer for wireless wearable communication applications.

Wearable devices have provided noninvasive and continuous monitoring of physiological parameters in healthcare applications. However, for the comfortable applications of wearable devices on human body, two key requirements are to replace conventional bulky devices into soft and deformable ones and to have wireless wearable communication. In this paper we present a simple, low-cost and highly efficient all-elastomeric conductor that can be used in a soft radio-frequency (RF) transmission line and antenna. We show a stretchable transmission line and two stretchable antennas fabricated with conventional screen printing. The stretchable conductor used in this fabrication method, which is a mixture of Ag and Polydimethylsiloxane (PDMS), can be stretched at high strains while maintaining a high conductivity, low attenuation and feasible radiation performance. The measured conductivity of the stretchable conductor reaches 1000 S/cm. Additionally, the highly conductive printed Ag-PDMS is utilized to construct transmission lines and antennas. The performance of these stretchable components, especially under different conditions of bending, stretching and twisting, are experimentally examined in common wireless-communication frequency bands. Our results demonstrate that printed Ag-PDMS enabled RF passive components have the desired property and quality for wireless wearable communication applications, which would provide new opportunities for wearable healthcare electronics.

Ferrite Film Loaded Frequency Selective Metamaterials for Sub-GHz Applications.

Electromagnetic metamaterials are constructed with sub-wavelength structures that exhibit particular electromagnetic properties under a certain frequency range. Because the form-factor of the substructures has to be comparable to the wavelength of the operating frequency, few papers have discussed the metamaterials under GHz frequency. In this paper, we developed an innovative method to reduce the resonant frequency of metamaterals. By integrating the meta-structures with ferrite materials of higher permeability, the cell size of the meta-structure can be scaled down. This paper describes the methodology, design, and development of low-profile GHz ferrite loaded metamaterials. A ferrite film with a permeability of 20 could reduce the resonant frequency of metamaterials by up to 50%. A prototype has been fabricated and the measurement data align well with the simulation results. Because of the lowered operational frequency, the proposed ferrite loaded metamaterials offer more flexibility for various sub-GHz microwave applications, such as cloaks, absorbers, and frequency selective surfaces.

In-vitro testing of RF-enabled low force mechanical thrombectomy for ischemic stroke.

Mechanical thrombectomy for ischemic stroke has high recanalization rate, long treatment time window and low hemorrhage risk. However, the clot engagement approach of caging the clot against the vessel wall can cause vessel stenosis and stroke recurrence. A device with reduced radial stenting force that reduces vessel wall friction would minimize stenosis and damage. The use of localized Radio Frequency (RF) to enable clot engagement and retrieval with minimal stenting force is explored in this study. New mechanical thrombectomy devices enabled with RF (Patent No.: US 62/172,043) were built and tested on human blood clots in vessels ex vivo. Test results showed that the RF-mechanical thrombectomy successfully and reproducibly captured and retrieved the clots without relying on stent caging of the clot against the vessel wall. Further work will be conducted on animals to compare vessel wall damage between conventional and RF-mechanical thrombectomy.

Feasibility examination of isolated zonal thrombolysis using Raman spectroscopy.

Intravenous thrombolysis for the treatment of ischemic stroke requires long treatment time and high drug dosage which increases the risk of hemorrhage. Localized zonal dosage of urokinase between 100 - 500 International Units (IU), i.e., less than 5% of typical systemic dosage (60,000 - 120,000 IU) at the thrombus can shorten the treatment time to less than 30 minutes while reducing the risk of hemorrhage. The effect of zonal-delivered urokinase on the molecular changes in a 100 µm thick by 20 mm diameter blood clot was quantified using Raman spectroscopy. In situ Raman spectra showed that the fibrin concentration in the clot decreased with time. The results verified that a zonal-delivered urokinase can dissolve the clot and reduce the treatment time. Further trials on animals will be conducted to examine the potential of zonal-delivery to accelerate clot dissolution for ischemic stroke while minimizing the risk of hemorrhage.

One-Step Preparation of Silver Hexagonal Microsheets as Electrically Conductive Adhesive Fillers for Printed Electronics.

A facile one-step solution-phase chemical reduction method has been developed to synthesize Ag microsheets at room temperature. The morphology of Ag sheets is a regular hexagon more than 1 µm in size and about 200 nm in thickness. The hexagonal Ag microsheets possess a smoother and straighter surface compared with that of the commercial Ag micrometer-sized flakes prepared by ball milling for electrically conductive adhesives (ECAs). The function of the reagents and the formation mechanism of Ag hexagonal microsheets are also investigated. For the polyvinylpyrrolidone (PVP) and citrate facet-selective capping, the Ag atoms freshly reduced by N2H4 would orientationally grow alone on the {111} facet of Ag seeds, with the synergistically selective etching of irregular and small Ag particles by H2O2, to form Ag hexagonal microsheets. The hexagonal Ag microsheet-filled epoxy adhesives, as electrically conductive materials, can be easily printed on various substrates such as polyethylene terephthalate (PET), epoxy, glass, and flexible papers. The hexagonal Ag microsheet filled ECAs demonstrate lower bulk resistivity (approximately 8 × 10(-5) Ω cm) than that of the traditional Ag micrometer-sized-flake-filled ECAs with the same Ag content of 80 wt % (approximately 1.2 × 10(-4) Ω cm).

Enhanced Reduction of Graphene Oxide on Recyclable Cu Foils to Fabricate Graphene Films with Superior Thermal Conductivity.

Large-area freestanding graphene films are facilely fabricated by reducing graphene oxide films on recyclable Cu foils in H2-containing atmosphere at high temperature. Cu might act as efficient catalysts for considerably improved reduction of graphene oxide according to the SEM, EDS, XRD, XPS, Raman and TGA results. Comparing to the graphene films with ~30 µm thickness reduced without Cu substrate at 900 °C, the thermal conductivity and electrical conductivity of graphene films reduced on Cu foils are enhanced about 140% to 902 Wm(-1)K(-1) and 3.6 × 10(4) S/m, respectively. Moreover, the graphene films demonstrate superior thermal conductivity of ~1219 Wm(-1)K(-1) as decreasing the thickness of films to ~10 µm. The graphene films also exhibit excellent mechanical properties and flexibility.