A novel “dot” Janus particle is presented, which is compatible with optical traps and magnetic fields, allowing for direct control over five of the particle's degrees of freedom. With an additional constraint of the final sixth degree of freedom, this system represents the highest control ever achieved over freely suspended colloids, opening up the possibility for novel applications in intermolecular force measurement, microfluidics, and self‐assembly.

Despite the recent progress in physical control and manipulation of various condensed matter, atomic, and particle systems, including individual atoms and photons, our ability to control topological defects remains limited. Recently, controlled generation, spatial translation, and stretching of topological point and line defects have been achieved using laser tweezers and liquid crystals as model defect-hosting systems. However, many modes of manipulation remain hindered by limitations inherent to optical trapping. To overcome some of these limitations, we integrate holographic optical tweezers with a magnetic manipulation system, which enables fully holonomic manipulation of defects by means of optically and magnetically controllable colloids used as "handles" to transfer forces and torques to various liquid crystal defects. These colloidal handles are magnetically rotated around determined axes and are optically translated along three-dimensional pathways while mechanically attached to defects, which, combined with inducing spatially localized nematic-isotropic phase transitions, allow for geometrically unrestricted control of defects, including previously unrealized modes of noncontact manipulation, such as the twisting of disclination clusters. These manipulation capabilities may allow for probing topological constraints and the nature of defects in unprecedented ways, providing the foundation for a tabletop laboratory to expand our understanding of the role defects play in fields ranging from subatomic particle physics to early-universe cosmology.

We present a micropatterning method for the automatic transfer and arbitrary positioning of computer-generated three-dimensional structures within a substrate. The Gerchberg-Saxton algorithm and an electrically addressed spatial light modulator (SLM) are used to create and display phase holograms, respectively. A holographic approach to light manipulation enables arbitrary and efficient parallel photo-patterning. Multiple pyramidal microstructures were created simultaneously in a photosensitive adhesive. A scanning electron microscope was used to confirm successful replication of the desired microscale structures.

We present a quantitative phase microscopy method that uses a Bayer mosaic color camera to simultaneously acquire off-axis interferograms in transmission mode at two distinct wavelengths. Wrapped phase information is processed using a two-wavelength algorithm to extend the range of the optical path delay measurements that can be detected using a single temporal acquisition. We experimentally demonstrate this technique by acquiring the phase profiles of optically clear microstructures without 2π ambiguities. In addition, the phase noise contribution arising from spectral channel crosstalk on the color camera is quantified. © 2010 Optical Society of America OCIS codes: 090.5694, 090.4220, 100.5088, 180.3170. Transmission-geometry quantitative phase microscopy (QPM) has been developed for three-dimensional measurement and characterization of a wide variety of transparent samples, such as transparent optical elements (e.g., microlens arrays) [1], optical fibers [2], and living cells [3,4]. This interferometric measurement of optical path delays (OPDs) provides quantitative contrast arising from both the physical height of the sample and its refractive index changes. While QPM provides diffractionlimited lateral resolution and nanometer-scale axial resolution of OPDs, the axial range over which the phase can be unambiguously determined is limited to 2π, which corresponds to one full wavelength of the illumination light.To solve the 2π ambiguities in the acquired phase profiles and determine the correct relative OPDs across a field of view, two-dimensional unwrapping algorithms are typically employed. Classic unwrapping algorithms are based on gradient minimization, which adds multiples of 2π at specific points in the phase map [5]. While these algorithms can accurately recover a smooth and slowly varying phase map, they frequently fail to accurately reconstruct objects containing a phase difference greater than π between adjacent image pixels.An alternative approach to overcoming the limitations of phase unwrapping is the use of multiple illumination wavelengths. By processing the phase profiles obtained from different wavelengths, it becomes possible to synthesize a single phase profile that is unambiguous over the range of the "beat" wavelength [6,7], which is larger than the unambiguous range that results from using a single wavelength independently. Because this approach is based on an analytical solution and not an iterative numerical method, two-wavelength phase unwrapping is particularly useful when classic unwrapping algorithms fail to correctly unwrap across sharp phase discontinuities.Two-wavelength phase unwrapping has been previously employed in reflection-geometry QPM using both sequential [8] and simultaneous [9,10] illumination/ detection schemes to accurately reconstruct surface profiles of highly reflective structures. Two-wavelength phase unwrapping has also been used for transmissiongeometry phase microscopy [1,11]; however, these methods use sequential illumination and detection, which require...

We demonstrate a diffractive maskless lithographic system that is capable of rapidly performing both serial and single-shot micropatterning. Utilizing the diffractive properties of phase holograms displayed on a spatial light modulator, arbitrary intensity distributions were produced to form two and three dimensional micropatterns/structures in a variety of substrates. A straightforward graphical user interface was implemented to allow users to load templates and change patterning modes within the span of a few minutes. A minimum resolution of ~700 nm is demonstrated for both patterning modes, which compares favorably to the 232 nm resolution limit predicted by the Rayleigh criterion. The presented method is rapid and adaptable, allowing for the parallel fabrication of microstructures in photoresist as well as the fabrication of protein microstructures that retain functional activity.