Simultaneous fabrication of hybrid arrays of nanowires and micro/nanoparticles by dewetting on micropillars

Controlled Fabrication of DNA Molecular Templates for In Situ Formation and Measurement of Ultrathin Metal Nanostructures

Fabrication of ultrathin metal nanostructures usually requires some combination of high-vacuum deposition and postgrowth processing, which precludes access to nanostructures of ultrasmall cross sections for most materials. DNA nanowires (NWs) are versatile insulating templates with intrinsic sub-10 nm line width. Here, we demonstrate a method of DNA template fabrication with precise control over the location and orientation of the DNA NWs. We further demonstrate that this template can be used to support formation of ultrathin metal NWs for derivative nanodevices: a metal is incrementally deposited, and electrical transport measurement is performed in situ at each step. The results show a homogeneous metal NW is obtained at a thickness as small as 0.9 nm with a cross-section of only a few nm². The high degree of control in the location, separation, and orientation of the DNA NWs affords this method great promise in fabricating complex nanodevices based on metal NWs.

Flow of DNA in micro/nanofluidics: From fundamentals to applications

Thanks to direct observation and manipulation of DNA in micro/nanofluidic devices, we are now able to elucidate the relationship between the polymer microstructure and its rheological properties, as well as to design new single-molecule platforms for biophysics and biomedicine. This allows exploration of many new mechanisms and phenomena, which were previously unachievable with conventional methods such as bulk rheometry tests. For instance, the field of polymer rheology is at a turning point to relate the complex molecular conformations to the nonlinear viscoelasticity of polymeric fluids (such as coil-stretch transition, shear thinning, and stress overshoot in startup shear). In addition, nanofluidic devices provided a starting point for manipulating single DNA molecules by applying basic principles of polymer physics, which is highly relevant to numerous processes in biosciences. In this article, we review recent progress regarding the flow and deformation of DNA in micro/nanofluidic systems from both fundamental and application perspectives. We particularly focus on advances in the understanding of polymer rheology and identify the emerging research trends and challenges, especially with respect to future applications of nanofluidics in the biomedical field.

Using micro to manipulate nano

A "Micro to nano" dewetting strategy is presented to generate multi-direction-controlled, precise-positioning 1D assemblies of conductive silver (Ag) NPs based on a superhydrophobicity-directed assembly strategy. Electrons can transport along linear NP assemblies and their behavior is sustained by coating a coaxial protecting layer outside the nanostructures. This new concept might open new routes for NP-based nanoelectronic circuit fabrication.

"Liquid-liquid-solid"-type superoleophobic surfaces to pattern polymeric semiconductors towards high-quality organic field-effect transistors

Precisely aligned organic-liquid-soluble semiconductor microwire arrays have been fabricated by "liquid-liquid-solid" type superoleophobic surfaces directed fluid drying. Aligned organic 1D micro-architectures can be built as high-quality organic field-effect transistors with high mobilities of >10 cm(2) ·V(-1) ·s(-1) and current on/off ratio of more than 10(6) . All these studies will boost the development of 1D microstructures of organic semiconductor materials for potential application in organic electronics.

Low-cost fabrication of centimetre-scale periodic arrays of single plasmid DNA molecules

We report the development of a low-cost method to generate a centimetre-scale periodic array of single plasmid DNA molecules of 11 kilobase pairs. The arrayed DNA molecules are amenable to enzymatic and physical manipulations.

Numerical and Experimental Studies on DNA Combing Used in Fabricating Nanochannel Electroporation (NEP) Chips

Microelectromechanical processes were used to generate a stamp with array of micro pillars. This stamp was subjected to DNA combing and imprinting to form nanostrands between the micro pillars, followed by sputter coating with gold, vapour deposition and imprinting processes in order to produce the required nanochannels for the gene chip. These preparation processes have been widely used to create implementations for cell manipulation and electroporation. However, the underlying mechanism of DNA stretching has only been demonstrated experimentally and is not fully understood. It, therefore, arrives unstable yield rate when process parameters are changed. This study investigated the DNA combing and imprinting processes using two-phase flow and moving mesh methods to analyse the variation of flow field at the micron level. It shows that while withdrawing from water, a smaller velocity difference in each location and the velocity difference of pillars are the major determinants of DNA stretching and curing. The simulation results showed that a bigger α and θ led to a greater difference in flow velocity on the PDMS stamp surface; greater flow velocity difference could affect the adhesion of DNA (subsequently compromising the formation of the nanochannels). As suggested by our experimental data, longer nanochannels (3 μm) displayed a wider range of stretching speed with yield rate >90%.

Small molecular nanowire arrays assisted by superhydrophobic pillar-structured surfaces with high adhesion

Elaborately programmed fluorescent calcein nanowire arrays can be prepared with the aid of superhydrophobic pillar-structured surfaces with high adhesion. Each nanowire can be precisely positioned by well designed tip-structured micropillars, indicating an advance in the methodologies of controlling small molecular 1D organic nanostructures. The as-prepared fluorescent nanowire arrays can serve as a ferrous salt sensing device.

Elaborate positioning of nanowire arrays contributed by highly adhesive superhydrophobic pillar-structured substrates

Elaborate positioning of nanowire arrays can be generated upon highly adhesive superhydrophobic pillar-structured silicon substrates. The site of each nanowire can be precisely positioned by well designed tip-structured micropillars, yielding on-demand nanowire patterns. This approach might affect existing applications and enable new opportunities in organically functional devices and bio/chemical sensors.

Patterning nanowire and micro-nanoparticle array on micropillar-structured surface: Experiment and modeling

DNA molecules in a solution can be immobilized and stretched into a highly ordered array on a solid surface containing micropillars by molecular combing technique. However, the mechanism of this process is not well understood. In this study, we demonstrated the generation of DNA nanostrand array with linear, zigzag, and fork-zigzag patterns and the microfluidic processes are modeled based on a deforming body-fitted grid approach. The simulation results provide insights for explaining the stretching, immobilizing, and patterning of DNA molecules observed in the experiments.