Punching Dense Colloidal Fluids
Displacement (or force) chains that develop in a dense colloidal fluid that is perturbed periodic radial "punching" using a single colloid that is held and moved in an optical tweezer.
Poynting Vector Power Flow
The transverse Poynting vectors of an optical matter machine. The seven blue circles represent silver nanoparticles, each with a radius of 75 nanometers. These nanoparticles are arranged into a hexagonal optical matter machine by a polarized beam of light shining down on them. When trapped this way, the nanoparticles convert the spin angular momentum of the light into orbital angular momentum, like a gear driven by a crank. The flow of orbital angular momentum can be seen in the arrows of the Poynting vectors. This flow of momentum can be used to do work on the nanoscale, such as moving other nanoparticles around.
Conventional vs Super-Resolution Imaging
A comparison of conventional wide-field imaging (left) and super-resolution structured illumination microscopy (SIM) (right). This image of a live human fibroblast cell shows microtubules in red, actin in yellow, mitochondria in green, and DNA in blue. To achieve this high resolution in just one color, the excitation light is patterned by the array of mirrors in a digital micromirror device (DMD) that is tuned to the precise wavelength of the excitation light. Typically, if multiple colors of light were shone on the DMD, each would reflect at a different angle, rather than toward the sample cell. To capture these four colors simultaneously, the four excitation wavelengths must first be separated by diffraction grating, then refocused onto the DMD—this counteracts the varying angles of reflection and allows all four to reach the cell. This grating-DMD technology makes it possible to observe many different cell structures at the same time with extremely high resolution.