Boo Hyun An

Fabrication of monolithic polymer nanofluidic channels using nanowires as sacrificial templates.

We report a facile and reliable method to fabricate polymer-based monolithic nanofluidic channels. The nanochannels are obtained via three main steps: (1) fabrication of nanowire-transistor like structures, which are silver or zinc oxide nanowires horizontally bridging two electrodes made of zinc oxide on SiO(2)/Si substrates; (2) casting and curing polyimide solution on the nanowire structures; and (3) selective etching of the nanowire and electrode templates against the polyimide substrates. This process leads to the production of nanochannels with a diameter down to ∼ 50 nm. Our method is based on nanowires that are chemically synthesized whereas nanopattern fabrication conventionally relies on expensive equipment. Moreover, the polymer nanochannels are fabricated monolithically while a process of bonding two different materials is required in traditional methods where leakage problems are often identified at the interface. Construction of nanofluidic circuitry could be expected in the future based on the current work.

Effects of Cu doping on the microstructure and magnetic properties of CoPt nanowires

We studied the effects of copper doping on the microstructure and magnetic properties of CoPt nanowires fabricated in anodized aluminium oxide (AAO) nanotemplates by electrodeposition. The morphological observation indicates well-formed CoPt and CoPtCu nanowires, while the structural analysis shows that fcc-Co3Pt phase exists prior to annealing and is retained in the doped nanowires, with minor hcp-CoPt phase postannealing. The doping causes shrinkage of the lattice spacing prior to annealing due to the insertion of smaller copper atoms. Compared to the undoped CoPt nanowires, the magnetic measurements reveal significant enhancement in the magnetic properties of the CoPtCu nanowire postannealing, resulting in the more rapid increase in the coercivity with annealing temperature.

Radio frequency-mediated local thermotherapy for destruction of pancreatic tumors using Ni–Au core–shell nanowires

We present a novel method of radio frequency (RF)-mediated thermotherapy in tumors by remotely heating nickel (Ni)-gold (Au) core-shell nanowires (CSNWs). Ectopic pancreatic tumors were developed in nude mice to evaluate the thermotherapeutic effects on tumor progression. Tumor ablation was produced by RF-mediated thermotherapy via activation of the paramagnetic properties of the Ni-Au CSNWs. Histopathology demonstrated that heat generated by RF irradiation caused significant cellular death with pyknotic nuclei and nuclear fragmentation dispersed throughout the tumors. These preliminary results suggest that thermotherapy ablation induced via RF activation of nanowires provides a potential alternative therapy for cancer treatment.

Ultrahigh Tensile Strength Nanowires with a Ni/Ni-Au Multilayer Nanocrystalline Structure

Superior mechanical properties of nanolayered structures have attracted great interest recently. However, previously fabricated multilayer metallic nanostructures have high strength under compressive load but never reached such high strength under tensile loads. Here, we report that our microalloying-based electrodeposition method creates a strong and stable Ni/Ni-Au multilayer nanocrystalline structure by incorporating Au atoms that makes nickel nanowires (NWs) strongest ever under tensile loads even with diameters exceeding 200 nm. When the layer thickness is reduced to 10 nm, the tensile strength reaches the unprecedentedly high 7.4 GPa, approximately 10 times that of metal NWs with similar diameters, and exceeding that of most metal nanostructures previously reported at any scale.

Magnetic NiFe/Au barcode nanowires with self-powered motion

NiFe/Au barcode nanowires were synthesized by pulsed electrodeposition using anodic aluminum oxide nanotemplate, comprising magnetic, catalytic, and optical segments, respectively. The self-powered motion of the BNWs due to the catalytic reaction was observed in aqueous H2O2. The approach demonstrates how sophistication in barcode nanoarchitecture can be used to synthesize a wide range of hybrid materials.

Micro-capacitor with vertically grown silver nanowires and bismuth ferric oxide composite structures on silicon substrates:

We have designed and demonstrated a complementary metal-oxide-semiconductor compatible process for fabricating high capacitance micro-capacitors based on vertically grown silver nanowires on silicon substrates. Array of silver nanowires with high-aspect ratio were electrochemically grown in the pores of anodized aluminum oxide film, which was pre-formed through anodization of aluminum thin film deposited on titanium/silicon oxide/silicon substrates. High dielectric bismuth ferric oxide layer was electrodeposited to fill the gap between silver nanowires after anodized aluminum oxide film was removed. It was found that the micro-capacitor based on the silver nanowires/bismuth ferric oxide composite film possessed higher capacitance by approximately one order of magnitude from the COMSOL simulation results from the flat Ag thin-film capacitor and the silver nanowire capacitor.