Increasing the penetration depth for ultrafast laser tissue ablation using glycerol based optical clearing

Background: Deep tissue ablation is the next challenge in ultrafast laser microsurgery. By focusing ultrafast pulses below the tissue surface one can create an ablation void confined to the focal volume. However, as the ablation depth increases in a scattering tissue, increase in the required power can trigger undesired nonlinear phenomena out of focus that restricts our ability to ablate beyond a maximum ablation depth of few scattering lengths. Optical clearing (OC) might reduce the intensity and increase the maximal ablation depth by lowering the refractive index mismatch, and therefore reducing scattering. Some efforts to ablate deeper showed out of focus damage, while others used brutal mechanical methods for clearing. Our clinical goal is to create voids in the scarred vocal folds and inject a biomaterial to bring back the tissue elasticity and restore phonation. Materials and methods: Fresh porcine vocal folds were excised and applied a biocompatible OC agent (75% glycerol). Collimated transmittance was monitored. The tissue was optically cleared and put under the microscope for ablation threshold measurements at different depths. Results: The time after which the tissue was optically cleared was roughly two hours. Fitting the threshold measurements to an exponential decay graph indicated that the scattering length of the tissue increased to 83±16 μm, which is more than doubling the known scattering length for normal tissue. Conclusion: Optical clearing with Glycerol increases the tissue scattering length and therefore reduces the energy for ablation and increases the maximal ablation depth. This technique can potentially improve clinical microsurgery

Microfluidic devices for the rapid and automated processing of sample populations

Microfluidic devices for the rapid and automated processing of sample populations are provided. Described are multiplexer microfluidic devices configured to serially deliver a plurality of distinct sample populations to a sample processing element rapidly and automatically, without cross-contaminating the distinct sample populations. Also provided are microfluidic sample processing elements that can be used to rapidly and automatically manipulate and/or interrogate members of a sample population. The microfluidic devices can be used to improve the throughput and quality of experiments involving model organisms, such as C. elegans.Board of Regents, University of Texas Syste

An Automated Microfluidic Multiplexer for Fast Delivery of C. elegans Populations from Multiwells

Automated biosorter platforms, including recently developed microfluidic devices, enable and accelerate high-throughput and/or high-resolution bioassays on small animal models. However, time-consuming delivery of different organism populations to these systems introduces a major bottleneck to executing large-scale screens. Current population delivery strategies rely on suction from conventional well plates through tubing periodically exposed to air, leading to certain disadvantages: 1) bubble introduction to the sample, interfering with analysis in the downstream system, 2) substantial time drain from added bubble-cleaning steps, and 3) the need for complex mechanical systems to manipulate well plate position. To address these concerns, we developed a multiwell-format microfluidic platform that can deliver multiple distinct animal populations from on-chip wells using multiplexed valve control. This Population Delivery Chip could operate autonomously as part of a relatively simple setup that did not require any of the major mechanical moving parts typical of plate-handling systems to address a given well. We demonstrated automatic serial delivery of 16 distinct C. elegans worm populations to a single outlet without introducing any bubbles to the samples, causing cross-contamination, or damaging the animals. The device achieved delivery of more than 90% of the population preloaded into a given well in 4.7 seconds; an order of magnitude faster than delivery modalities in current use. This platform could potentially handle other similarly sized model organisms, such as zebrafish and drosophila larvae or cellular micro-colonies. The device’s architecture and microchannel dimensions allow simple expansion for processing larger numbers of populations.The authors would like to thank the National Institutes of Health (www.nih.gov) for its generous support of this research. Specifically, the grants that made this work possible are the NIH Director's Transformative Award (NIH R01 AG041135), NIH R21 NS067340, and NIH R01 NS060129. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Biomedical EngineeringElectrical and Computer EngineeringMechanical Engineerin

Synthesis of Glass Nanofibers Using Femtosecond Laser Radiation Under Ambient Condition

We report the unique growth of nanofibers in silica and borosilicate glass using femtosecond laser radiation at 8 MHz repetition rate and a pulse width of 214 fs in air at atmospheric pressure. The nanofibers are grown perpendicular to the substrate surface from the molten material in laser-drilled microvias where they intertwine and bundle up above the surface. The fibers are few tens of nanometers in thickness and up to several millimeters in length. Further, it is found that at some places nanoparticles are attached to the fiber surface along its length. Nanofiber growth is explained by the process of nanojets formed in the molten liquid due to pressure gradient induced from the laser pulses and subsequently drawn into fibers by the intense plasma pressure. The attachment of nanoparticles is due to the condensation of vapor in the plasma

Femtosecond laser nanoablation of glass in the near-field of single wall carbon nanotube bundles

Abstract This paper presents an experimental study on the femtosecond (fs) laser ablation of bundles of single wall carbon nanotubes (SWCNTs) deposited on glass and the resulting nanoablation of glass beneath the bundles. The peak ablation threshold of SWCNT bundles is 50 ± 12 mJ cm −2 , which is about ten times lower than the theoretical ablation threshold of individual SWCNTs. Nanoscale ablation of the glass surface (30-50 nm wide, 20-50 nm deep and micrometres long) directly beneath the bundles is possible at a laser fluence of 920 ± 76 mJ cm −2 , which is 4-5 times lower than the fs laser ablation threshold of glass. We attribute these reduced ablation thresholds to the enhancement of fs laser pulses in the near-field of nanotube bundles. This nanoablation approach can be used for lithographical and surgical applications requiring nanoscale precision

Plasmonic laser nanoablation methods

A novel femtosecond laser nano-ablation technique called Plasmonic Laser Nano-Ablation (PLN). The technique takes advantage of surface-enhanced plasmonic scattering of ultrashort laser pulses by nanoparticles to vaporize sub-cellular structures in attoliter volumes. The use of nanoparticles may overcome problems associated with current FLMS techniques and does not rely on heating for nanodisruption. In PLN, the particle acts as a “nano-lens,” restricting laser light to the near-field of the particle, and only photodisrupting structures that are nanometers away. This eliminates the need for a tightly focused beam, while still achieving nanoscale ablation resolution. Moreover, the enhanced scattering around the particles reduces the amount of required laser fluence. A method is provided comprising positioning a nanoparticle in proximity to a surface of a material; irradiating the nanoparticle with a laser tuned close to the nanoparticle's plasmonic frequency; and allowing a near-field effect from the irradiated nanoparticle to photodamage the material.Board of Regents, University of Texas Syste