David G. Grier

A revolution in optical manipulation.

Optical tweezers use the forces exerted by a strongly focused beam of light to trap and move objects ranging in size from tens of nanometres to tens of micrometres. Since their introduction in 1986, the optical tweezer has become an important tool for research in the fields of biology, physical chemistry and soft condensed matter physics. Recent advances promise to take optical tweezers out of the laboratory and into the mainstream of manufacturing and diagnostics; they may even become consumer products. The next generation of single-beam optical traps offers revolutionary new opportunities for fundamental and applied research.

Dynamic holographic optical tweezers

Optical trapping is an increasingly important technique for controlling and probing matter at length scales ranging from nanometers to millimeters. This paper describes methods for creating large numbers of high-quality optical traps in arbitrary three-dimensional configurations and for dynamically reconfiguring them under computer control. In addition to forming conventional optical tweezers, these methods also can sculpt the wavefront of each trap individually, allowing for mixed arrays of traps based on different modes of light, including optical vortices, axial line traps, optical bottles and optical rotators. The ability to establish large numbers of individually structured optical traps and to move them independently in three dimensions promises exciting new opportunities for research, engineering, diagnostics, and manufacturing at mesoscopic lengthscales.

The charge of glass and silica surfaces

We present a method of calculating the electric charge density of glass and silica surfaces in contact with aqueous electrolytes for two cases of practical relevance that are not amenable to standard techniques: surfaces of low specific area at low ionic strength and surfaces interacting strongly with a second anionic surface.

Optical tweezer arrays and optical substrates created with diffractive optics

We describe a simple method for creating multiple optical tweezers from a single laser beam using diffractive optical elements. As a demonstration of this technique, we have implemented a 4×4 square array of optical tweezers—the hexadeca tweezer. Not only will diffractively generated optical tweezers facilitate many new experiments in pure and applied physics, but they also will be useful for fabricating nanocomposite materials and devices, including photonic bandgap materials and optical circuit elements.

Computer-generated holographic optical tweezer arrays

Holographic techniques significantly extend the capabilities of laser tweezing, making possible extended trapping patterns for manipulating large numbers of particles and volumes of soft matter. We describe practical methods for creating arbitrary configurations of optical tweezers using computer-generated diffractive optical elements. While the discussion focuses on ways to create planar arrays of identical tweezers, the approach can be generalized to three-dimensional arrangements of heterogeneous tweezers and extended trapping patterns.

Microoptomechanical pumps assembled and driven by holographic optical vortex arrays.

Beams of light with helical wavefronts can be focused into ring-like optical traps known as optical vortices. The orbital angular momentum carried by photons in helical modes can be transferred to trapped mesoscopic objects and thereby coupled to a surrounding fluid. We demonstrate that arrays of optical vortices created with the holographic optical tweezer technique can assemble colloidal spheres into dynamically reconfigurable microoptomechanical pumps assembled by optical gradient forces and actuated by photon orbital angular momentum.

Manipulation and assembly of nanowires with holographic optical traps.

We demonstrate that semiconductor nanowires can be translated, rotated, cut, fused and organized into nontrivial structures using holographic optical traps. The holographic approach to nano-assembly allows for simultaneous independent manipulation of multiple nanowires, including relative translation and relative rotation.

Characterizing and tracking single colloidal particles with video holographic microscopy

We use digital holographic microscopy and Mie scattering theory to simultaneously characterize and track individual colloidal particles. Each holographic snapshot provides enough information to measure a colloidal spheres radius and refractive index to within 1%, and simultaneously to measure its three-dimensional position with nanometer in-plane precision and 10 nanometer axial resolution.

Holographic optical trapping

Holographic optical tweezers use computer-generated holograms to create arbitrary three-dimensional configurations of single-beam optical traps that are useful for capturing, moving, and transforming mesoscopic objects. Through a combination of beam-splitting, mode-forming, and adaptive wavefront correction, holographic traps can exert precisely specified and characterized forces and torques on objects ranging in size from a few nanometers to hundreds of micrometers. Offering nanometer-scale spatial resolution and real-time reconfigurability, holographic optical traps provide unsurpassed access to the microscopic world and have found applications in fundamental research, manufacturing, and materials processing.

Mesoscopic self‐assembly of gold islands on diblock‐copolymer films

We describe the fabrication and characterization of self‐assembled gold island arrays on diblock‐copolymer thin films. The natural tendency of these polymers to form ordered phases is used to induce selective aggregation of evaporated gold metal during an annealing process. We obtain well‐defined, nanoscale island arrays aligned with one of the copolymer blocks. Near perfect segregation is achieved between the two domains. Two types of diblock‐copolymer systems are discussed, together with the resulting island patterns.