1,720,974 research outputs found
Polymeric fully inertial lab-on-a-chip with enhanced-throughput sorting capabilities
Full text linkIn biology and medicine, the application of microfluidics filtration technologies to the separation of rare particles requires processing large amounts of liquid in a short time to achieve an effective separation yield. In this direction, the parallelization of the sorting process is desirable, but not so easy to implement in a lab on a chip (LoC) device, especially if it is fully inertial. In this work, we report on femtosecond laser microfabrication (FLM) of a poly(methyl methacrylate) (PMMA) inertial microfluidic sorter, separating particles based on their size and providing an enhanced-throughput capability. The LoC device consists of a microchannel with expansion chambers provided with siphoning outlets, for a continuous sorting process. Different from soft lithography, which is the most used technique for LoC prototyping, FLM allows developing 3D microfluidic networks connecting both sides of the chip. Exploiting this capability, we are able to parallelize the circuit while keeping a single output for the sorted particles and one for the remaining sample, thus increasing the number of processed particles per unit time without compromising the simplicity of the chip connections. We investigated several device layouts (at different flow rates) to define a configuration that maximizes the selectivity and the throughput
Editorial for the Special Issue on New Trends and Applications in Femtosecond Laser Micromachining
Full text linkFemtosecond laser micromachining is becoming an established fabrication technique for transparent material processing in three dimensions [...]
Femtosecond laser microfabrication of a PMMA lab on a chip for high throughput size-based inertial sorting
No full textInertial microfluidic particles sorting represents a critical task in many areas of biology, biotechnology, and medicine, including the isolation from blood of rare target cell populations, like e.g. circulating tumor cells (CTCs) and circulating fetal cells (CFCs). Usually, cell sorter microfluidic devices are fabricated by PDMS soft lithography, which is the most widespread micromanufacturing platform enabling to cost-effectively produce Lab-on-a-Chip with resolution in the nanometer scale. However, this technology presents some drawbacks: (i) due to PDMS softness, especially for high-pressure flows, the microfluidic behavior may change along the devices, leading to ambiguous results; (ii) soft-lithography allows to pattern structures on just one side of the chip thus limiting the affordable geometries to enhance the throughput of target particles. In this work, we develop a PMMA continuous size-based inertial microfluidic sorter by femtosecond laser microfabrication (FLM). The device design includes contracting and expanding channels (microchambers) provided with siphoning outlets on the backside of the chip. Since FLM technology is in principle applicable to any type of polymer, we chose PMMA, which is a biocompatible and transparent thermoplastic polymer much stiffer than PDMS. FLM allows machining the microfluidic network on both sides of the chip, making it possible the parallelization of the sorting process. In addition, thanks to the FLM flexibility, we easily varied the chambers number and the collecting strategy (at different flow rates) in order to define a device layout maximizing the trapping efficiency and throughput
Integrated fast optical switch fabricated by femtosecond laser micromachining
Full text linkIntegrated optical switches and modulators allow performing reconfigurability in integrated circuits, resulting as fundamental components in different fields ranging from optical communications to sensing and metrology. Among different methods, the thermo-optic effect has been successfully used to fabricate optical modulators by femtosecond laser micromachining (FLM) in glass substrates, proving high stability, no losses dependance but long switching time. In this work, we present an integrated optical switch realized by FLM with a switching time of less than 1 ms: which is about 1 order of magnitude faster than the other devices present in literature. This result has been achieved by carefully optimizing the geometry and the position of resistors and trenches near the waveguides through simulation and experimental validation. In addition, by means of an optimization of the applied voltage signal, we have demonstrated a further significant temporal improvement, measuring a switching time of less than 100 μs
Strategies for improved temporal response of glass-based optical switches
Full text linkWe present an optimization of the dynamics of integrated optical switches based on thermal phase shifters. These devices have been fabricated in the volume of glass substrates by femtosecond laser micromachining and are constituted by an integrated Mach–Zehnder interferometer and a superficial heater. Simulations, surface micromachining and innovative layouts allowed us to improve the temporal response of the optical switches down to a few milliseconds. In addition, taking advantage of an electrical pulse shaping approach where an optimized voltage signal is applied to the heater, we proved a switching time as low as 78 μs, about two orders of magnitude shorter with respect to the current state of the art of thermally-actuated optical switches in glass
Effects of thermal annealing on femtosecond laser micromachined glass surfaces
Full text linkFemtosecond laser micromachining (FLM) of fused silica allows for the realization of three-dimensional embedded optical elements and microchannels with micrometric feature size. The performances of these components are strongly affected by the machined surface quality and residual roughness. The polishing of 3D buried structures in glass was demonstrated using different thermal annealing processes, but precise control of the residual roughness obtained with this technique is still missing. In this work, we investigate how the FLM irradiation parameters affect surface roughness and we characterize the improvement of surface quality after thermal annealing. As a result, we achieved a strong roughness reduction, from an average value of 49 nm down to 19 nm. As a proof of concept, we studied the imaging performances of embedded mirrors before and after thermal polishing, showing the capacity to preserve a minimum feature size of the reflected image lower than μ5μm. These results allow for us to push forward the capabilities of this enabling fabrication technology, and they can be used as a starting point to improve the performances of more complex optical elements, such as hollow waveguides or micro-lenses
A computational approach to the characterization of a microfluidic device for continuous size-based inertial sorting
No full textThe application of fully-inertial size-based microfluidic filtration technologies for particle separation is an attractive tool, which not only offers label-free control of the microenvironment during separation, but also facilitates integration and automation for high throughput sample processing. In this work, we exploit 3D computational fluid dynamics (CFD) simulations based on the lattice Boltzmann method to evaluate the performance of a microfluidic device specifically designed to trap and extract particles by inertial focusing and microscale vortices. The device geometry consists of a straight microchannel, followed downstream by a microchamber with outlets for continuous size-based separation. Simulations were carried out to characterize the flow properties of the microfluidic device. Here, the influence of the Reynolds number (Re), the chamber dimensions and the outlet channels aspect ratio on the streamtracer distribution were studied. In order to support the simulation results, some preliminary experimental validations have been conducted, finding that the model can accurately characterize the flow in the studied geometry. The results of the simulations and experiments presented in this paper can be very useful to support the design of continuous-flow particle sorting lab-on-a-chip (LOC) devices
Three-dimensional and dual-color fluorescence microscopy on a chip
Full text linkIn this work we present two microscopes on chip based on Light Sheet Fluorescence Microscopy, capable to automatically perform 3D and dual-color imaging of specimens diluted in a liquid suspension. A microfluidic channel is used for automatic sample delivery, while integrated optical components such as optical waveguides and lenses are used to illuminate the sample flowing in the channel. The devices are fabricated by femtosecond laser micromachining in a glass substrate. Benefiting from the versatility of the fabrication technique we present two prototypes that have been optimized for different samples such as single cells and Drosophila embryos
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