Rapid prototyping methods for the design and fabrication of polymeric labs-on-a-chip are on the rise, as they allow high degrees of precision and flexibility. For example, a microfluidic platform may require an optimization phase in which it could be necessary to continuously modify the architecture and geometry; however, this is only possible if easy, controllable fabrication methods and low-cost materials are available. In this paper, we describe the realization process of a microfluidic tool, from the computer-aided design (CAD) to the proof-of-concept application as a capture device for circulating tumor cells (CTCs). The entire platform was realized in polymethyl methacrylate (PMMA), combining femtosecond (fs) laser and micromilling fabrication technologies. The multilayer device was assembled through a facile and low-cost solvent-assisted method. A serpentine microchannel was then directly biofunctionalized by immobilizing capture probes able to distinguish cancer from non-cancer cells without labeling. The low material costs, customizable methods, and biological application of the realized platform make it a suitable model for industrial exploitation and applications at the point of care.

La finalità di questo progetto è, investigare e sviluppare tecnologie altamente innovative, che possano estremizzare l'efficienza dei motori termici verso l'obiettivo del 50%. Per raggiungere questo risultato, oltre all'impiego di tecnologie estremamente avanzate, sarà riconsiderato il concetto stesso di motore endotermico, rivoluzionando l'attuale ciclo termodinamico di riferimento. Per massimizzare l'impatto del progetto, tutte le tecnologie sviluppate saranno orientate all'utilizzo di combustibili alternativi, come per esempio il biometano: la potenziale produzione italiana di biometano può soddisfare il fabbisogno di combustibile di 1/3 dei veicoli attualmente circolanti sul territorio nazionale. Di fatto è già stato appurato che senza una vera e propria rivoluzione nella tecnologia delle batterie e del sistema elettrico europeo, i motori termici ad alta efficienza alimentati con combustibili rinnovabili, quali biometano e biofuel di seconda generazione, hanno, oltre che emissioni inquinanti quasi nulle, un'emissione di CO2 sul ciclo di vita del veicolo (incluso produzione, dismissione e riciclo) inferiore ai corrispondenti veicoli elettrici. Questo fattore, accoppiato alla capacità di implementazione immediata delle tecnologie proposte alle motorizzazioni tradizionali, per i quali è già presente un'infrastruttura di rifornimento capillare sull'intero territorio europeo, può garantire una risposta efficace agli obiettivi dell'Europa di riduzione dei gas serra a breve e medio termine, sanciti con l'accordo di Parigi. Le finalità sopra descritte afferiscono al dominio tecnologico della progettazione, produzione e gestione di sistemi di propulsione (powertrain) ed è principalmente orientata allo sviluppo dei settori industriali legati ai trasporti stradali e alle relative filiere produttive. Inoltre, le tecnologie sviluppate possono contribuire in maniera significativa alla decarbonizzazione, all'efficientamento energetico e alla sostenibilità ambientale, potendo essere trasversalmente impiegate in tutti i settori in cui si fa impiego dei motori a combustione interna, dal trasporto ferroviario e marittimo alle applicazioni off road e di cogenerazione di energia.

In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.

This paper presents an experimental study where a vision camera integrates coaxially into a laser beam welding tool to monitor beam deviations (beam offset) in laser stake welding of T-joints. The aim is to obtain an early detection of deviations from the joint centreline in this type of welding where the joint is not visible from the top side. A polynomial surface fitting method is applied to extract features that can describe the behaviour of the melt pool. A nonlinear autoregressive with exogenous inputs neural network model is trained to relate eight image features to the laser beam offset. The performance of the presented model is evaluated offline by different welding samples. The results show that the proposed method can be used to guide post weld inspection and has the potential for on-line adaptive control.

The single-pulse laser hardening of a hypereutectoid steel coated by a graphite layer was investigated using a numerical/experimental approach. Experimental tests were conducted on coated samples using a fibre laser source and without any gas shielding aiming to explore the effect of laser power, pulse energy and defocusing distance on the dimensions of the hardened region. The process operating window of the discrete spot laser hardening using the graphite layer was determined through a finite element model and compared with previous results obtained on uncoated samples. For the same laser power and interaction times, an enlargement of the hardened region was found when using the graphite coating, especially when operating at the lowest laser energy level. The process operating window remains similar in shape to the one of the uncoated steel but moves towards larger hardened diameters and much larger defocusing distances. Once the maximum temperature has been fixed, a linear relationship between the hardened diameter and the defocusing distance exists. No obvious surface oxidation occurs since the graphite coating acts as a protective layer.

In this work, nanocomposites based on polyethylene oxide (PEO) and copper nanoparticles (CuNPs) for food packaging application were developed as new active packaging for fresh foodstuffs. Copper colloids were synthesized by femtosecond-pulsed laser ablation synthesis in solution (LASiS) using an organic environment, to ensure a good solubility of nanocolloids in polymeric solution. CuNPs were incorporated in a biodegradable polymer matrix for the preparation of composite films. Besides a deep morphological and spectroscopic characterization, bioactive ions release over time from composite thin films was studied by atomic absorption spectroscopy. Finally, in vivo tests on fresh-cut fruit were carried out to assess the effects of these nanocomposite systems on product quality. CuNPs-PEO composites were found effective to prevent quality decay of fruit salad. In particular, the active films allowed better preserving color and texture of fruit that remained acceptable for 3-4 days more than the control sample.

Inertial 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).

In this work, we report on the fabrication of laser induced periodic surface structures (LIPSS) on stainless steel, using bursts of 200 fs sub-pulses at a wavelength of 1030 nm. A cascade of birefringent crystals was used to generate the bursts with tunable number of sub-pulses and intra-burst delays varying between 1.5 ps and 24 ps. Being such a delay shorter than the typical electron-lattice relaxation time in metals, the sub-pulses impinge on the sample surface when the material is still in a transient state after excitation from the first sub-pulse, thus allowing peculiar structures to be generated depending on the burst features.

Laser-induced textures have been proven to be excellent solutions for modifying wetting, friction, biocompatibility, and optical properties of solids. The possibility to generate 2D-submicron morphologies by laser processing has been demonstrated recently. Employing double-pulse irradiation, it is possible to control the induced structures and to fabricate novel and more complex 2D-textures. Nevertheless, double-pulse irradiation often implies the use of sophisticated setups for modifying the pulse polarization and temporal profile. Here, we show the generation of homogeneous 2D-LIPSS (laser-induced periodic surface structures) over large areas utilizing a simple array of birefringent crystals. Linearly and circularly polarized pulses were applied, and the optimum process window was defined for both. The results are compared to previous studies, which include a delay line, and the reproducibility between the two techniques is validated. As a result of a systematic study of the process parameters, the obtained morphology was found to depend both on the interplay between fluence and inter-pulse delay, as well as on the number of incident pulses. The obtained structures were characterized via SEM (scanning electron microscopy) and atomic force microscopy. We believe that our results represent a novel approach to surface structuring, primed for introduction in an industrial environment.

The capability of isolating and sorting specific types of cells is crucial in life science, particularly for the early diagnosis of lethal diseases and monitoring of medical treatments. Among all the micro-fluidics techniques for cell sorting, inertial focusing combined with the laminar vortex technology is a powerful method to isolate cells from flowing samples in an efficient manner. This label-free method does not require any external force to be applied, and allows high throughput and continuous sample separation, thus offering a high filtration efficiency over a wide range of particle sizes. Although rather recent, this technology and its applications are rapidly growing, thanks to the development of new chip designs, the employment of new materials and microfabrication technologies. In this review, a comprehensive overview is provided on the most relevant works which employ inertial focusing and laminar vortex technology to sort particles. After briefly summarizing the other cells sorting techniques, highlighting their limitations, the physical mechanisms involved in particle trapping and sorting are described. Then, the materials and microfabrication methods used to implement this technology on miniaturized devices are illustrated. The most relevant evolution steps in the chips design are discussed, and their performances critically analyzed to suggest future developments of this technology.

We investigate the short and long term wettability of laser textured stainless steel samples in order to better understand the interplay between surface topography and chemistry. Very different 1D and 2D periodic as well as non-periodic surface patterns were produced by exploiting the extreme flexibility of a setup consisting of five rotating birefringent crystals, which allows generating bursts of up to 32 femtosecond laser pulses with fixed intra-burst delay of 1.5 ps. The change of the surface morphology as a function of the pulse splitting, the burst polarization state and the fluence was systematically studied. The surface topography was characterized by SEM and AFM microscopy. The laser textured samples exhibited, initially, superhydrophilic behaviour which, during exposure to ambient air, turned into superhydrophobic with an exponential growth of the static contact angle. The dynamic contact angle measurements revealed a water adhesive character which was explained by XPS analyses of the surfaces that showed an increase of hydrocarbons and more oxidized metal species with the aging. The characteristic water adhesiveness and superhydrophobicity of laser textured surfaces can be exploited for no loss droplet reversible transportation or harvesting.

The femtosecond laser technology is emerging as a powerful and flexible tool for the fabrication of miniaturized polymeric devices, thanks to the micrometric precision and the minimum thermal damage on the workpiece obtainable through ultrafast laser ablation. However, parametrization of femtosecond laser processes is often based on a trial and error approach, which requires a lot of expensive experimental efforts. The design of experiment (DoE) approach can offer a methodical way to quickly determine the laser process settings limiting the use of resources. In this work, we define an accurate DoE procedure to estimate the influence of the laser repetition rate, pulse energy, scanning speed, and hatch distance on the fs-laser micromilling process of PMMA specimens in terms of depth of removed material (Dh). We show that the laser pulse energy is the parameter that mainly affects the milling depth. A predictive model describing the relationship between the response variable depth and the main laser parameters is defined and then validated.

Robotized laser beam welding of closed-square-butt joints is sensitive to the positioning of the laser beam with respect to the joint since even a small offset may result in a detrimental lack of sidewall fusion. An evaluation of a system using a photodiode aligned coaxial to the processing laser beam confirms the ability to detect variations of the process conditions, such as when there is an evolution of an offset between the laser beam and the joint. Welding with different robot trajectories and with the processing laser operating in both continuous and pulsed mode provided data for this evaluation. The detection method uses wavelet analysis of the photodetector signal that carries information of the process condition revealed by the plasma plume optical emissions during welding. This experimental data have been evaluated offline. The results show the potential of this detection method that is clearly beneficial for the development of a system for welding joint tracking.

Bursts of linearly polarised femtosecond laser pulses with variable intra-burst delays on the picosecond timescale and different number of sub-pulses were used to produce laser-induced periodic surface structures (LIPSS) on stainless steel surfaces. The influence on the LIPSS morphology of the number sub-pulses, from 2 to 32, and the time separation between them, from 1.5 ps to 24 ps, was systematically investigated and compared to the case of unsplit pulses. The spatial periods and depths of the LIPSS produced by different irradiation conditions were derived by scanning electron and atomic force microscopies revealing that, in case of bursts with only two sub-pulses, an increase of the intra-burst delay produces nanoripples with higher spatial separation but shallower depth which is ascribed to a shielding effect. Whereas, increasing the number of sub-pulses a slight increase of the LIPSS spatial period has been observed.

In 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.

In this paper, a femtosecond laser manufacturing process is effectively employed to produce a pattern of micro dimples on a fluoroelastomer. To quantify the microtexture tribological performance, two configurations are implemented: non-conformal and conformal contacts are tested on a pin-on-disk tribometer. Due to the reduced number of dimples engaged in the contact region, no significant friction enhancement is obtained in the non-conformal configuration. On the contrary, in the case of conformal contacts, outstanding outcomes in terms of friction reduction - up to 60% - can be achieved by a properly designed micro-texture. Such a result is obtained by improving the wear debris entrapment and the cavitation respectively at low and high speed, without increasing significantly the occurrence of flow eddies.

Lab-on-chips (LoCs) are microsystems capable of manipulating small amounts of fluids in microfluidic channels. They have a huge application potential, from basic science to chemical synthesis and point-of-care medical analysis. Polymers are rapidly emerging as the substrate of choice for LoC production, thanks to a low material cost and ease of processing. Two breakthroughs that could promote LoC diffusion are a microfabrication technology with cost-effective and rapid prototyping capabilities and also an integrated on-chip optical detection system. This chapter proposes the use of femtosecond laser micromachining combined with microinjection moulding as a novel highly-flexible microfabrication platform for polymeric LoCs with integrated optical detection, for the realization of low-cost and truly portable biophotonic microsystems. We demonstrate a LoC for the relevant application of non-invasive and contactless mechanical phenotyping of single cancer cells.

Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.

We report on an experimental study of the incubation effect during irradiation of stainless steel targets with bursts of femtosecond laser pulses at 1030 nm wavelength and 100 kHz repetition rate. The bursts were generated by splitting the pristine 650-fs laser pulses using an array of birefringent crystals which provided time separations between sub-pulses in the range from 1.5 ps to 24 ps. We measured the threshold fluence in Burst Mode, finding that it strongly depends on the bursts features. The comparison with Normal Pulse Mode revealed that the existing models introduced to explain the incubation effect during irradiation with trains of undivided pulses has to be adapted to describe incubation during Burst Mode processing. In fact, those models assume that the threshold fluence has a unique value for each number of impinging pulses in NPM, while in case of BM we observed different values of threshold fluence for fixed amount of sub-pulses but different pulse splitting. Therefore, the incubation factor coefficient depends on the burst features. It was found that incubation effect is higher in BM than NPM and that it increases with the number of sub-pulses and for shorter time delays within the burst. Two-Temperature-Model simulations in case of single pulses and bursts of up to 4 sub-pulses were performed to understand the experimental results.

Robotized laser beam welding of closed-square-butt joints is sensitive to how the focused laser beam is positioned in relation to the joint, and existing joint tracking systems tend to fail in detecting the joint when the gap and misalignment between the work pieces are close to zero. A camera-based system is presented based on a high dynamic range camera operating with LED illumination at a specific wavelength and a matching optical filter. An image processing algorithm based on the Hough transform extracts the joint position from the camera images, and the joint position is then estimated using a Kalman filter. The filter handles situations, when the joint is not detectable in the image, e.g., when tack welds cover the joint. Surface scratches, which can be misinterpreted as being the joint, are handled by a joint curve prediction model based on known information about the nominal path defined by the robot program. The performance of the proposed system has been evaluated off line with image data obtained during several welding experiments.