Propagation of designer surface plasmons in structured conductor surfaces with parabolic gradient index.

In this work, we investigate the propagation of designer surface plasmons in planar perfect electric conductor structures that are subject to a parabolic graded-index distribution. A three-dimensional, fully vectorial finite-difference time-domain method was used to engineer a structure with a parabolic effective group index by modulating the dielectric constant of the structure's square holes. Using this structure in our simulations, the lateral confinement of propagating designer surface plasmons is demonstrated.

Active molecular plasmonics: controlling plasmon resonances with molecular switches.

A gold nanodisk array, coated with bistable, redox-controllable [2]rotaxane molecules, when exposed to chemical oxidants and reductants, undergoes switching of its plasmonic properties reversibly. By contrast, (i) bare gold nanodisks and (ii) disks coated with a redox-active, but mechanically inert, control compound do not display surface-plasmon-based switching. Along with calculations based on time-dependent density functional theory, these experimental observations suggest that the nanoscale movements within surface-bound "molecular machines" can be used as the active components in plasmonic devices.

Biological and biomimetic molecular machines.

The evolution of life facilitates the creation of biological molecular machines. In these so-called 'nanomachines,' nature elegantly shows that when precisely organized and assembled, simple molecular mechanical components can link motions efficiently from the nanometer scale to the macroscopic world, and achieve complex functions such as powering skeletal muscles, synthesizing ATP and producing DNA/RNA. Inspired by nature, researchers are creating artifical molecular machines with tailored structures and properties, with the aim of realizing man-made active nanosystems that operate with the same efficiency and complexity as biological nanomachines.

Focusing microparticles in a microfluidic channel with standing surface acoustic waves (SSAW).

We introduce a novel on-chip microparticle focusing technique using standing surface acoustic waves (SSAW). Our method is simple, fast, dilution-free, and applicable to virtually any type of microparticle.

Nanoporous polymeric transmission gratings for high-speed humidity sensing.

Nanoporous polymeric transmission gratings are demonstrated to be an excellent platform for high-speed optical humidity sensing. The grating structures were fabricated with a modified holographic, polymer-dispersed liquid crystal (H-PDLC) system. The sensing mechanism was based on changes in the relative transmission associated with the adsorption and desorption of water vapour by nanopores.

Hydrodynamically tunable optofluidic cylindrical microlens.

In this work, we report the design, fabrication, and characterization of a tunable optofluidic microlens that focuses light within a microfluidic device. The microlens is generated by the interface of two co-injected miscible fluids of different refractive indices, a 5 M CaCl(2) solution (n(D) = 1.445) and deionized (DI) water (n(D) = 1.

"Microfluidic drifting"--implementing three-dimensional hydrodynamic focusing with a single-layer planar microfluidic device.

We introduce a novel fluid manipulation technique named "microfluidic drifting" to enable three-dimensional (3D) hydrodynamic focusing with a simple single-layer planar microfluidic device.

Linear artificial molecular muscles.

Two switchable, palindromically constituted bistable [3]rotaxanes have been designed and synthesized with a pair of mechanically mobile rings encircling a single dumbbell. These designs are reminiscent of a "molecular muscle" for the purposes of amplifying and harnessing molecular mechanical motions. The location of the two cyclobis(paraquat-p-phenylene) (CBPQT(4+)) rings can be controlled to be on either tetrathiafulvalene (TTF) or naphthalene (NP) stations, either chemically ((1)H NMR spectroscopy) or electrochemically (cyclic voltammetry), such that switching of inter-ring distances from 4.

An electrochemical detection scheme for identification of single nucleotide polymorphisms using hairpin-forming probes.

Single nucleotide polymorphisms are implicated as having a significant role in regulating growth, development and, thereby, human health and disease. We have developed a method for identifying single nucleotide genetic alterations by combining hairpin-forming DNA probes and electrochemical detection of sandwich DNA hybridization. Incorporation of hairpin-forming competitor probes and the catalyzed reporter deposition amplification system further improves assay specificity by 7-fold and sensitivity by 100-fold.