Laser transfer for circulating tumor cell isolation in liquid biopsy.

75Cancer research has found in the recent years a formidable ally in liquid biopsy, a noninvasive technique that allows the study of circulating tumor cells (CTCs) and biomolecules involved in the dynamics of cancer spread like cell-free nucleid acids or tumor-derived extracellular vesicles. However, single-cell isolation of CTCs with high viability for further genetic, phenotypic, and morphological characterization remains a challenge. We present a new approach for single CTC isolation in enriched blood samples using a liquid laser transfer (LLT) process, adapted from standard laser direct write techniques. In order to completely preserve the cells from direct laser irradiation, we used an ultraviolet laser to produce a blister-actuated laser-induced forward transfer process (BA-LIFT). Using a plasma-treated polyimide layer for blister generation, we completely shield the sample from the incident laser beam. The optical transparency of the polyimide allows direct cell targeting using a simplified optical setup, in which the laser irradiation module, standard imaging, and fluorescence imaging share a common optical path. Peripheral blood mononuclear cells (PBMCs) were identified by fluorescent markers, while target cancer cells remained unstained. As a proof of concept, we were able to isolate single MDA-MB-231 cancer cells using this negative selection process. Unstained target cells were isolated and culture while their DNA was sent for single-cell sequencing (SCS). Our approach appears to be an effective approach to isolate single CTCs, preserving cell characteristics in terms of cell viability and potential for further SCS.

Picosecond Laser Shock Micro-Forming of Stainless Steel: Influence of High-Repetition Pulses on Thermal Effects.

A study of the peen forming of thin stainless steel metal foils (50 µm thick) using a solid-state ps-pulsed laser, emitting at a wavelength of 1064 nm was conducted. The pitch distance between consecutive laser pulses was kept constant by tuning the laser repetition rate from 0.4 to 10 kHz, and subsequently the scanning speed. The induced bending angle and the radius of curvature were used to measure the effect of the treatment. Their dependence on the pulse energy, the treated area, the distance between lines, and the laser repetition rate was studied. High repetition rates do not allow the sample to cool down, affecting the bending to the point of being negligible. An FEM simulation and experiments were carried out to prove that the increase in temperature due to high repetition rate can relax the stresses induced by laser peen treatment, thus preventing bending in the sample.

Sputtered Non-Hydrogenated Amorphous Silicon as Alternative Absorber for Silicon Photovoltaic Technology.

Non-hydrogenated amorphous-silicon films were deposited on glass substrates by Radio Frequency magnetron sputtering with the aim of being used as precursor of a low-cost absorber to replace the conventional silicon absorber in solar cells. Two Serie of samples were deposited varying the substrate temperature and the working gas pressure, ranged from 0.7 to 4.5 Pa. The first Serie was deposited at room temperature, and the second one, at 325 °C. Relatively high deposition rates above 10 Å/s were reached by varying both deposition temperature and working Argon gas pressure to ensure high manufacturing rates. After deposition, the precursor films were treated with a continuous-wave diode laser to achieve a crystallized material considered as the alternative light absorber. Firstly, the structural and optical properties of non-hydrogenated amorphous silicon precursor films were investigated by Raman spectroscopy, atomic force microscopy, X-ray diffraction, reflectance, and transmittance, respectively. Structural changes were observed in the as-deposited films at room temperature, suggesting an orderly structure within an amorphous silicon matrix; meanwhile, the films deposited at higher temperature pointed out an amorphous structure. Lastly, the effect of the precursor material's deposition conditions, and the laser parameters used in the crystallization process on the quality and properties of the subsequent crystallized material was evaluated. The results showed a strong influence of deposition conditions used in the amorphous silicon precursor.

Influence of the Gap between Substrates in the Laser-Induced Transference of High-Viscosity Pastes.

Laser-induced forward transfer for high-viscosity-of Pa·s-pastes differ from standard LIFT processes in its dynamics. In most techniques, the transference after setting a great gap does not modify the shape acquired by the fluid, so it stretches until it breaks into droplets. In contrast, there is no transferred material when the gap is bigger than three times the paste thickness in LIFT for high-viscosity pastes, and only a spray is observed on the acceptor using this configuration. In this work, the dynamics of the paste have been studied using a finite-element model in COMSOL Multiphysics, and the behavior of the paste varying the gap between the donor and the acceptor substrates has also been modeled. The paste bursts for great gaps, but it is confined when the acceptor is placed close enough. The obtained simulations have been compared with a previous work, in which the paste structures were photographed. The analysis of the simulations in terms of speed allows for predicting the burst of the paste-spray regime-and the construction of a printability map regarding the gap between the substrates.

Thermal Effects in the Ablation of Bovine Cortical Bone with Pulsed Laser Sources.

Lasers have advantages as bone surgical tools over mechanical methods, but two goals should be achieved to assure its use: Similar ablation rates to those obtained with mechanical tools (1 mm3/s at least) and to avoid thermal damage, a condition that can prevent proper bone healing. We present results of cow femoral bone with a 355 nm nanosecond (ns) and a 1064 nm picosecond (ps) pulsed laser sources that allow us to discuss the influence on the process of pulse duration and the selective ablation through high energy absorption (as bone highly absorbs 355 nm radiation). The treated samples were characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The evaluation of the thermal effects produced in the samples shows clear differences between both laser sources: On one hand, the ns laser allows reaching high ablation rates (around 1 mm3/s); Raman spectra show no signal of bone carbonization, but unavoidable thermal effects in the form of melted and solidified material have been observed by electron microscopy in the samples treated with this laser. On the other hand, ablation without any sign of thermal effects is obtained using the ps laser, but with lower ablation rates, (around 0.15 mm3/s).