Hongke Ye

Integrating nanowires with substrates using directed assembly and nanoscale soldering

This paper describes a new methodology for integrating nanowires with micropatterned substrates using directed assembly and nanoscale soldering. Nanowires containing ferromagnetic nickel segments were fabricated by electrodeposition in nanoporous membranes. The nanowires were released by dissolution of the membrane and subsequently aligned relative to micropatterned substrates using magnetic field-directed assembly. After assembly, the wires were permanently bonded to the substrates using solder reflow to form low-resistance electrical contacts. This is the first demonstration of the use of nanoscale solder reflow to form low-resistance electrical interconnects between nanowires and substrates, and we demonstrated the utility of the strategy by fabricating a nanowire-based functional analog integrator.

Reconfigurable Microfluidics With Metallic Containers

We describe a microfluidic scheme based on remotely controlled self-assembled containers that allows spatio-temporal control over nanoliter-scale chemical reactions. We discuss finite-element simulations of the inductive coupling of radio-frequency radiation to the containers; this coupling enables remotely triggered release of chemical reactants. We demonstrate on-demand chemical release from stationary and mobile containers patterned with different porosities. We also explore reactions between chemicals released from two containers that form liquid products and deposit solid precipitates. We argue that these remotely controlled metallic containers provide an attractive platform for carrying out reconfigurable microfluidics ldquowithout channels.rdquo.

Forming low resistance nano-scale contacts using solder reflow

We describe the use of solder reflow on the 100 nanometer scale to form electrically conductive contacts. We fabricated nanowires using electrodeposition in nanoporous templates. We investigated the use of directed assembly and nanoscale soldering to integrate the nanowires with microfabricated bond pads, and measured the electrical characteristics of the soldered wires. The electrical resistance of a single nanowire on top of two adjacent contact pads dropped by an order of magnitude after solder reflow. The results in this paper demonstrate that it is possible to use solder films as thin as 100 nm to electrically bond nanocomponents to substrates with contact resistances as low as 5 /spl Omega/.

Microfabrication and Self-Assembly of 3D Microboxes for Biomedical Applications

This paper reports a novel method for fabricating three dimensional (3D) metallic micropatterned boxes by self-assembly of two dimensional (2D) precursors. A 3D micropatterned device has several advantages over its two dimensional (2D) counterpart—a larger surface area to volume ratio, thereby maximizing interactions with the surrounding medium and providing space to mount different electromechanical modules, and a finite volume allowing encapsulation of functional elements. The microboxes can be constructed in different sizes with perforations on either one or on all faces. We demonstrate encapsulation of gels and polymers within the boxes, and release of chemicals by heating. We envision the use of these boxes in cellular encapsulation and remote release of drugs and biological media in-vitro and in-vivo.