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We demonstrate the growth of high-quality GaN films with flat surface and uniform morphology on large-scale polycrystalline chemical vapor-deposited graphene films. The films exhibit stimulated emission even at room temperature, a highly c-axis-oriented crystal structure, and a preferred in-plane orientation. Furthermore, the GaN films grown on the graphene films can be used for fabrication of blue and green light-emitting diodes.
Barcodes that composed of multiple colloidal crystal or magnetic-tagged ETPTA cores and PEG hydrogel shells were developed by using microfluidics. As the cores are with distinct reflection peaks, the barcodes allow for substantial number of coding levels for multiplexing. The hydrogel shells surrounding the barcodes enable the creation of three-dimensional scaffolds for immobilizing probes. Moreover, the presence of magnetism in the barcodes confer them controllable movement under magnetic fields, which could significantly increase the sensitivity and simplify the processing of the bioassays.
We report the first attempt of magnetic manipulation of photoresponse in an one-dimensional device, in which a highly sensitive photodetector in the UV region composed of tin oxide nanowire and ferromagnetic nickel electrodes have been fabricated and characterized. Surprisingly, as the Nickel electrodes were magnetized, the photocurrent gain can be greatly enhanced by up to 20 times. The underlying mechanism is attributed to both oxygen molecules adsorbed and surface band bending effects due to the migration of electrons to the surface of tin oxide nanowire caused by the magnetic field of ferromagnetic electrodes.
We report a microfluidic chip integrated with a bioengineered membrane for two-dimensional (2D) and three-dimensional (3D) spheroid tissue cultures to achieve deterministic patterning of cells. The cell-supporting membrane was selectively deposited with extracellular matrix molecules. Results show cell-trapping rate attains 97%. Tuning of the surface enables not only highly controlled geometry of the monolayer (2D) cell mass but also 3D culture of uniformly sized multicellular spheroids. The 3D spheroids of human ovarian epithelial cancer cells acquired mesenchymal traits—increased expressions of N-cadherin, vimentin and fibronectin—and lowered expression of epithelial marker (CD326/epithelial cell adhesion molecule) compared with that in 2D cultures, indicative of epithelial–mesenchymal transition. These results offer new opportunities to achieve active control of 2D cellular patterns and 3D multicellular spheroids on demand, and may be amenable toward study of the metastatic process in vitro.
Increasing the Seebeck coefficient has long been pursued for increasing thermoelectric efficiency, but other changes in transport properties may compensate this effect and ultimately lead to no improvement in figure of merit. The Seebeck coefficient can be enhanced by either the addition of resonant states or the involvement of multiple band conduction. This work demonstrates the beneficial effect of multiple band conduction for highefficiency thermoelectrics.
