Original Article

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.

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.

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 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.

We present a facile and reliable approach for the assembly of crack-free single-crystalline photonic crystals (PCs) with centimeter scale by the synergistic effects of substrate deformation and monomer infiltration/polymerization. The critical thickness of crack-free PCs is ∼5.6 μm, below which crack-free PCs can be fabricated on proper substrate. The co-assembling monomer infiltrates and polymerizes in the interstices of the colloidal spheres to form an elastic polymer network, which could lower the tensile stress generated from colloid shrinkage and strengthen the long range interactions of the colloidal spheres. Otherwise, the timely transformation of the flexible substrate releases the residual stress. This approach to centimeter-scale crack-free single-crystalline PCs will not only prompt the practical applications of PCs in high-performance optic devices, but also have great implications for the fabrication of crack-free thin films in other fields, such as wet clays, coating and ceramic industry.

Strain-driven micro- and nanorolls fabrication is generally restricted to multilayer and multiprocessing systems, which limit the possibility of exploiting the self-organization at different length scales. We have designed a hybrid organic–inorganic film whose surface shows a selective response to external stimuli, which induces mechanical strain and self-rolling in one-step–one-layer fabrication. The scrolling is initiated by water and any aqueous solution that also contains molecules or colloidal particles. During scrolling, the different species in solution remain entrapped in the rolls, giving rise to functional microrolls.

High-power applications at fast charge and discharge rates are still great challenges in the development of rechargeable lithium batteries. Here, we demonstrate that ultralong LiV₃O₈ nanowire cathode materials synthesized by topotactic Li intercalation present excellent high-rate and long-life performance. At the current density of 2000, mA g⁻¹, the initial and the six-hundredth discharge capacities can reach 137 and 120 mAh g⁻¹, respectively, corresponding to a capacity fading of only 0.022% per cycle. Such performance indicates that the topotactically synthesized ultralong LiV₃O₈ nanowires are promising cathode materials for high-rate and long-life rechargeable lithium batteries.

Highly conductive and stretchable conductors from bacterial cellulose (BC) can be fabricated through a simple and inexpensive method using bacterial cellulose pellicles as starting materials, which can be produced in large amounts on an industrial scale via a microbial fermentation process. The prepared pyrolyzed BC/polydimethylsiloxane composites exhibit highly stable electric conductivity even under high stretching and bending strain.

Regular microhelics on a heterogenous spindle knot are obtained by controlled biaxial stresses in three dimensions. The spindle knot has a tough core and a brittle shell, resulting in biaxial stresses that arise from a thermal expansion mismatch during a heating process. Surface cleavage and interface delamination are harmonized due to the special spindle geometry and cooperate to 3D helical crack. This study not only widens our understanding of the cracking phenomena, but also sheds light on the control and design of regular cracks in arbitrary dimensions. It holds promise for applications in eliminating or controlling cracks for manufacturing process, especially at micro/nanosales, which domains are difficult to be generated by routine methods.

We have studied an unconventional polar switching associated with an electro–optical response in the columnar oblique phase of a dipeptide derivative. Observations were made using a large monodomain with the column axis perpendicular to substrates, as shown here. The interplay between polarity and chirality was found as the rotation of columns about the column axis, that is, the rotation angle linearly depends on an applied electric field and the rotational sense is reversed by either reversing the field direction or using opposite isomers. On the basis of the detailed SHG and FT-IR measurements, molecular and polar structures are shown.

Water-dispersed nanowires for phototherapy: Without passivation of any water-friendly functional groups in its backbone, one-dimensional zinc phthalocyanine nanowires show remarkably increased dispersibility in water. Upon irradiation with near infrared light, the zinc phthalocyanine nanowires exhibit dual photodynamic and photothermal properties, which enhance the cytotoxic efficiency against tumor cells.

A novel method based on the AuNPs for fast, sensitive and selective detection of Cu²⁺ was developed and applied in immunoassays.

Heusler compound spin injector with a high spin polarization dramatically improves the generation efficiency of the pure spin current compared with a conventional ferromagnetic metal.

We describe a novel method for liquid crystal (LC) alignment using nano-patterns of electrically conductive indium–tin oxide (ITO) layers with high resolution (ca<20 nm) and high aspect ratio (ca 8), fabricated based on the secondary sputtering phenomenon. The ITO pattern developed in this manner can function as an electrode and alignment layer at the same time, which facilitates successful fabrication of bifunctional conductive alignment layer for LC devices.

An electric field-enhanced transport gap is well established in a dual-gated field effect transistor (FET) based on the h-BN/single-layer graphene/h-BN sandwich structure, and the on/off current ratio is increased by a factor of 8.0 compared with pure single-layer graphene FET. The tunable and sizeable band gap and structural integrity render this sandwich structure a promising candidate for high-performance single-layer graphene FETs.

Schematics showing the switchable oil wettability of the P2VP-b-PDMS-grafted surface in aqueous media with different pH.

We have fabricated and tested encoders and decoders based on a multiplex, DNA-based electrochemical biosensor that uses electronic (electrochemical) signals as its readout. We have demonstrated these multifunctional, bio-electrochemical devices, for example, 4-to-2 and 8-to-3 encoders and 1-to-2 and 2-to-3 decoders. In doing so, these devices bridge the barrier between DNA-based devices and silicon-based electronics.

Indium-free quaternary chalcogenide, Cu₂ZnSnSe₄ (CZTSe), has driven much attention for its potential application in photovoltaics and optoelectronics. High-quality CZTSe nanocrystals (NCs) with thermodynamically metastable wurtzite phase were herein synthesized via a facile, lost-cost and safe-solution method, in which high reaction rate and low surface energy are favorable for the formation of wurtzite structure. The promising application of the as-synthesized NCs in photovoltaics and optoelectronics has been demonstrated by the high-performance hybrid photodetector made from CZTSe NCs and P3HT.

Where does carbon go when it is doped into magnesium diboride (MgB₂) and why the superconducting properties are improved? In this work, malic acid-doped MgB₂ was investigated and it was shown that carbon encapsulates boron powder, prevents agglomeration and as a result reduces void fraction as was confirmed by the first detailed X-ray tomogram analysis. It was also found that carbon induces a lot of stacking faults within MgB2 grains. The critical current density is now comparable to commercial niobium titanium (NbTi) wire and further improvements are expected.