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We present the use of Au bowtie nanoantenna arrays (BNAs) for highly efficient, multipurpose particle manipulation with unprecedented low input power and low-numerical aperture (NA) focusing. Optical trapping efficiencies measured are up to 20× the efficiencies of conventional high-NA optical traps and are among the highest reported to date. Empirically obtained plasmonic optical trapping "phase diagrams" are introduced to detail the trapping response of the BNAs as a function of input power, wavelength, polarization, particle diameter, and BNA array spacing (number density). Using these diagrams, parameters are chosen, employing strictly the degrees-of-freedom of the input light, to engineer specific trapping tasks including (1) dexterous, single-particle trapping and manipulation, (2) trapping and manipulation of two- and three-dimensional particle clusters, and (3) particle sorting. The use of low input power densities (power and NA) suggests that this bowtie nanoantenna trapping system will be particularly attractive for lab-on-a-chip technology or biological applications aimed at reducing specimen photodamage.

The formation of high-density silver nanoparticles and a novel method to precisely control the spacing between nanoparticles by temperature are demonstrated for a tunable surface enhanced Raman scattering substrates. The high-density nanoparticle thin film is accomplished by self-assembling through the Langmuir-Blodgett (LB) technique on a water surface and transferring the particle monolayer to a temperature-responsive polymer membrane. The temperature-responsive polymer membrane allows producing a dynamic surface enhanced Raman scattering substrate. The plasmon peak of the silver nanoparticle film red shifts up to 110 nm with increasing temperature. The high-density particle film serves as an excellent substrate for surface-enhanced Raman spectroscopy (SERS), and the scattering signal enhancement factor can be dynamically tuned by the thermally activated SERS substrate. The SERS spectra of Rhodamine 6G on a high-density silver particle film at various temperatures is characterized to demonstrate the tunable plasmon coupling between high-density nanoparticles.

An elastomer-based tunable liquid-filled microlens array integrated on top of a microfluidic network is fabricated using soft lithographic techniques. The simultaneous control of the focal length of all the microlenses composing the elastomeric array is accomplished by pneumatically regulating the pressure of the microfluidic network. A focal length tuning range of hundreds of microns to several millimeters is achieved. Such an array can be used potentially in dynamic imaging systems and adaptive optics.

Near infrared-absorbing gold nanoplasmonic particles (GNPs) are used as optical switches of gene interference and are remotely controlled using light. We have tuned optical switches to a wavelength where cellular photodamage is minimized. Optical switches are functionalized with double-stranded oligonucleotides. At desired times and at specific intracellular locations, remote optical excitation is used to liberate gene-interfering oligonucleotides. We demonstrate a novel gene-interfering technique offering spatial and temporal control, which is otherwise impossible using conventional gene-interfering techniques.Precise control of gene interference in living cells is in critical demand 1,2 for studying cellular signaling pathways, 3 quantitative cell biology, 4 systems biology, 5 and molecular cell biology. 6 In order to advance these dynamic cellular studies, nanoscale intracellular transmitter and receiver systems are required for the remote manipulation of biological systems. Remote electronic control of DNA hybridization by inductive coupling of radio frequency, 7 photouncaging of DNA by UV light, [8][9][10] and chromophore-based optical activation 11,12 of biomolecules have previously been demonstrated. Enzymes 13 and thermo-responsive polymers 14 have also been used to release biomolecules from carriers. Additionally, thermal ablation has previously been used to release large plasmids from carriers using high energy 15,16 or to destroy cells of interest. [17][18][19] However, gene interference with precise spatial and temporal resolution, minimal photodamage, as well as the selective coupling of the optical transmission frequency to different nanoscale transmitters has not yet been accomplished.Here, we present a new remote control switch of gene interference in living cells by using oligonucleotides on a nanoplasmonic carrier-based optical switch (ONCOS), short interfering oligonucleotides, and a near-infrared (NIR) laser transmitter. Gene interference by ONCOS occurs at the translational step. In the absence of gene interference, mRNA is transcribed from DNA in the nucleus and exported out to the cytoplasm (Figure 1b). The mRNA is then translated into the corresponding amino acids. This primary sequence of amino acids then folds into its final protein structure and is transported to the proper location in the cell. In the presence of ONCOS gene interference, optical switches are internalized within living cells ( Figure S1). The material, geometry, and size of these optical switches are specifically designed for use in ONCOS. GNPs are selected because of their stable and nontoxic properties in biological applications. 20,21 Rod-shaped GNPs have an aspect ratio (length/diameter) of 3.5, as shown in a scanning electron microscopy image in Figure 2b. Such geometry allows highly efficient photothermal conversion due to the matched resonant frequency, making it possible to activate gene release with minimized optical exposure time and low optical power. By carefully selecting the aspect ratio of these ...