Controlling the Surface Chemistry of a Hydrogel for Spatially Defined Cell Adhesion.

A two-step synthesis is described for activating the surface of a fully hydrated hydrogel that is of interest as a possible scaffold for neural regeneration devices. The first step exploits the water content of the hydrogel and the hydrophobicity of the reaction solvent to create a thin oxide layer on the hydrogel surface using a common titanium or zirconium alkoxide. This layer serves as a reactive interface that enables rapid transformation of the hydrophilic, cell-nonadhesive hydrogel into either a highly hydrophobic surface by reaction with an alkylphosphonic acid, or into a cell-adhesive one using a (α,ω-diphosphono)alkane.

Ultrafast z-scanning for high-efficiency laser micro-machining.

High-throughput laser micro-machining demands precise control of the laser beam position to achieve optimal efficiency, but existing methods can be both time-consuming and cost-prohibitive. In this paper, we demonstrate a new high-throughput micro-machining technique based on rapidly scanning the laser focal point along the optical axis using an acoustically driven variable focal length lens. Our results show that this scanning method enables higher machining rates over a range of defocus distances and that the effect becomes more significant as the laser energy is increased.

Photoluminescence of Functionalized Germanium Nanocrystals Embedded in Arsenic Sulfide Glass.

Embedding metallic and semiconductor nanoparticles in a chalcogenide glass matrix effectively modifies the photonic properties. Such nanostructured materials could play an important role in optoelectronic devices, catalysis, and imaging applications. In this work, we fabricate and characterize germanium nanocrystals (Ge NCs) embedded in arsenic sulfide thin films by pulsed laser ablation in aliphatic amine solutions.

Non-spherical particles for optical trap assisted nanopatterning.

Optical trap assisted nanopatterning is a laser direct-write technique that uses an optically trapped microsphere as a near-field objective. The type of feature that one can create with this technique depends on several factors, one of which is the shape of the microbead. In this paper, we examine how the geometry of the bead affects the focus of the light through a combination of experiments and simulations.

Parallel optical trap assisted nanopatterning on rough surfaces.

There exist many optical lithography techniques for generating nanostructures on hard, flat surfaces over large areas. However, few techniques are able to create such patterns on soft materials or surfaces with pre-existing structure. To address this need, we demonstrate the use of parallel optical trap assisted nanopatterning (OTAN) to provide an efficient and robust direct-write method of producing nanoscale features without the need for focal plane adjustment.