High-resolution 3D photopolymerization assisted by upconversion nanoparticles for rapid prototyping applications.

Three-dimensional (3D) rapid prototyping technology based on near-infrared light-induced polymerization of photocurable compositions containing upconversion nanomaterials has been explored. For this aim, the rationally-designed core/shell upconversion nanoparticles NaYF:Yb,Tm/NaYF, with the distinct ultraviolet-emitting lines and unprecedentedly high near-infrared to ultraviolet conversion efficiency of [Formula: see text] have been used. The upconverted ultraviolet photons were capable to efficiently activate photoinitiators contained in light-sensitive resins under moderate intensities of NIR excitation below 10 W cm and induce generation of radicals and photopolymerization in situ.

The influence of energy migration on luminescence kinetics parameters in upconversion nanoparticles.

The mechanism of upconversion at the nanoscale is still under discussion. In this paper, we report on the experimental results of anti-Stokes luminescence kinetics in the upconversion nanoparticles of β-NaYF: 20%Yb; 0.6%Tm.

Model for Optimization of the UV-A/Riboflavin Strengthening (cross-linking) of the Cornea: Percolation Threshold.

To achieve the maximum level of collagen strengthening within the shortest treatment time possible, we have developed a mathematical model which is used to optimize the process of corneal cross-linking. This model is able to predict the temporal and spatial distribution of generated cross-links within the corneal stroma and hence the increase in the elasticity modulus. Theory predicts corneal strengthening at low radiation intensities and the absence of the strengthening effect at radiation intensities above the threshold level, which agrees with the experimental results.

Incoherent wavefront reconstruction by a retroemission device.

This Letter addresses wavefront reconstruction by a retroemission device (REM). REM represents a lenslet array mounted on a substrate made of photoluminescent optical material, such as a polymer film impregnated with upconversion nanoparticles. An excitation light wavefront incident on the REM was sampled by the lenslet array piece-wise.

Feasibility study of the optical imaging of a breast cancer lesion labeled with upconversion nanoparticle biocomplexes.

Innovative luminescent nanomaterials, termed upconversion nanoparticles (UCNPs), have demonstrated considerable promise as molecular probes for high-contrast optical imaging in cells and small animals. The feasibility study of optical diagnostics in humans is reported here based on experimental and theoretical modeling of optical imaging of an UCNP-labeled breast cancer lesion. UCNPs synthesized in-house were surface-capped with an amphiphilic polymer to achieve good colloidal stability in aqueous buffer solutions.

Quantitative imaging of single upconversion nanoparticles in biological tissue.

The unique luminescent properties of new-generation synthetic nanomaterials, upconversion nanoparticles (UCNPs), enabled high-contrast optical biomedical imaging by suppressing the crowded background of biological tissue autofluorescence and evading high tissue absorption. This raised high expectations on the UCNP utilities for intracellular and deep tissue imaging, such as whole animal imaging. At the same time, the critical nonlinear dependence of the UCNP luminescence on the excitation intensity results in dramatic signal reduction at (∼1 cm) depth in biological tissue.

From scattering to wavefronts--what's in between?

Purpose: Some optical errors are too localized and random to be detected by commercial wavefront devices and Zernike polynomial expression. We looked beyond aberrations defined by Zernike expression to discuss implications of fine irregularities associated with highly aberrated corneal surfaces and complex surface roughness that can lead to light scattering.

Methods: Most fine irregularities are related to postoperative surface roughness, complexities of corneal ablation, and the laser in situ keratomileusis (LASIK) flap.