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Magnetically Driven Micromachines Created by Two-Photon Microfabrication and Selective Electroless Magnetite Plating for Lab-on-a-Chip Applications
Get PDFWe propose a novel method to fabricate three-dimensional magnetic microparts, which can be integrated in functional microfluidic networks and lab-on-a-chip devices, by the combination of two-photon microfabrication and selective electroless plating. In our experiments, magnetic microparts could be successfully fabricated by optimizing various experimental conditions of electroless plating. In addition, energy dispersive X-ray spectrometry (EDS) clarified that iron oxide nanoparticles were deposited onto the polymeric microstructure site-selectively. We also fabricated magnetic microrotors which could smoothly rotate using common laboratory equipment. Since such magnetic microparts can be remotely driven with an external magnetic field, our fabrication process can be applied to functional lab-on-a-chip devices for analytical and biological applications
Nanomechanical probing of soft matter through hydrophobic AFM tips fabricated by two-photon polymerization
No full textAtomic force microscopy (AFM) nanoindentation of soft materials is a powerful tool for probing mechanical properties of biomaterials. Though many results have been reported in this field over the last decade, adhesion forces between the tip and the sample hinder the elastic modulus measurement when hydrophilic soft samples are investigated. Here, two-photon polymerization (2PP) technology was used to fabricate hydrophobic perfluoropolyether-based AFM tips. The hydrophobic 2PP tips allowed us to overcome the limitations of commercial and functionalized tips as well as to successfully measure the elastic modulus of medically relevant soft materials in air. Our results obtained in the characterization of poly(dimethyl siloxane) and polyethylene glycol hydrogels showed lower adhesion forces over a larger measurement range when compared to measurements performed with commercial tips. The elastic moduli measured by means of hydrophobic 2PP AFM tips were also found to be comparable to those obtained using conventional techniques for macroscopic samples. We successfully showed that the hydrophobic AFM tips developed by this highly versatile technology enable the study of mechanical properties of soft matter, benefiting from reduced sample-tip interactions, and a custom-made shape and dimension of the tips
3d stem cell niche engineering via two-photon laser polymerization
No full textA strategy to modulate the behavior of stem cells in culture is to mimic structural aspects of the native cellâextracellular matrix (ECM) interaction. An important example of such artificial microenvironments for stem cell culture is the so-called âsynthetic niche.â Synthetic niches can be defined as polymeric culture systems mimicking at least one aspect of the interactions between stem cells and the extracellular surroundings, including biochemical factors (e.g., the delivery of soluble factors) and/or biophysical factors (e.g., the microarchitecture of the ECM). Most of the currently available approaches for scaffold fabrication, based on self-assembly methods, do not allow for a submicrometer control of the geometrical structure of the substrate, which might play a crucial role in stem cell fate determination. A novel technology that overcomes these limitations is laser two-photon polymerization (2PP). Femtosecond laser 2PP is a mask-less direct laser writing technique that allows manufacturing three dimensional arbitrary microarchitectures using photosensitive materials. Here, we report on the development of an innovative culture substrate, called the ânichoid,â microfabricated in a hybrid organicâinorganic photoresist called SZ2080, to study mesenchymal stem cell mechanobiology
Microstructured Phononic Crystal Isolates from Ultrasonic Mechanical Vibrations
Get PDFThe functioning of many micro-electromechanical devices with parts oscillating at high frequencies require isolation from external vibration. Phononic crystals, presenting band-gaps in the dispersion spectrum, i.e., interval of frequency in which propagating waves are attenuated, can provide an effective solution for vibration shielding at the microscale. In the present work, we design—through numerical simulations—a 3D phononic crystal with a micrometric unit cell able to work as vibration isolator for a micro system. We exploit the direct writing technique based on two-photon polymerization to realize three prototypes of different dimensions. Experimental measurements performed with a Michelson interferometer demonstrate the effectiveness of the proposal
Thermally reconfigurable quantum photonic circuits at telecom wavelength by femtosecond laser micromachining
Get PDFThe importance of integrated quantum photonics in the telecom band is based on the possibility of interfacing with the optical network infrastructure that was developed for classical communications. In this framework, femtosecond laser-written integrated photonic circuits, which have already been assessed for use in quantum information experiments in the 800-nm wavelength range, have great potential. In fact, these circuits, being written in glass, can be perfectly mode-matched at telecom wavelength to the in/out coupling fibers, which is a key requirement for a low-loss processing node in future quantumoptical networks. In addition, for several applications, quantum photonic devices must be dynamically reconfigurable. Here, we experimentally demonstrate the high performance of femtosecond laser-written photonic circuits for use in quantum experiments in the telecom band, and we demonstrate the use of thermal shifters, which were also fabricated using the same femtosecond laser, to accurately tune such circuits. State-of-the-art manipulation of single- and two-photon states is demonstrated, with fringe visibilities greater than 95%. The results of this work open the way to the realization of reconfigurable quantum photonic circuits based on this technological platform
Termoforesi in dispositivi microfluidici fabbricati mediante laser a femtosecondi
Get PDFLAUREA MAGISTRALELa termoforesi è un fenomeno di trasporto di particelle ad opera di un gradiente termico, che negli ultimi anni sta guadagnando attenzione per via della sua possibile applicazione come tecnica di separazione di particelle sulla base delle loro dimensioni e delle loro caratteristiche chimiche superficiali.
Di recente diverse tecniche di separazione hanno visto un'implementazione all'interno di dispositivi microscopici detti Lab-On-Chip (LOC). Questo nome è dovuto al fatto che essi racchiudono al proprio interno le funzionalità di diversi strumenti di laboratorio e permettono, grazie alle loro dimensioni molto ridotte, di indagare efficientemente fenomeni microscopici.
Per questi motivi è nata l'idea di effettuare esperimenti di termoforesi all'interno di un dispositivo microfluidico.
I dispositivi realizzati durante questo lavoro di tesi sono stati fabbricati mediante la tecnica detta Femtosecond Laser Irradiation followed by Chemical Etching (FLICE), che consiste nella creazione di modifiche permanenti all'interno di un chip di fused silica irraggiandolo con un laser impulsato a femtosecondi. Queste zone verranno poi erose selettivamente procedendo all'immersione del chip in una soluzione acida, creando una rete di microcanali.
Durante questo lavoro di tesi sono stati realizzati dispositivi secondo due diverse configurazioni.
La prima versione del dispositivo presenta tre canali paralleli, di cui i due laterali vengono utilizzati per far fluire acqua a due diverse temperature così da creare un gradiente termico uniforme in quello centrale. Questo contiene il campione che subisce l'effetto di trasporto dovuto alla termoforesi.
Il profilo di concentrazione che si stabilisce al suo interno è stato studiato con una tecnica ottica detta Differential Dynamic Microscopy, che permette di ricavare la concentrazione di particelle di dimensioni inferiori al limite di risoluzione del microscopio ottico analizzando il campo scatterato attraverso il campione stesso.
Nonostante sia stato possibile effettuare con successo diverse misure, il dispositivo ha mostrato alcune criticità.
In seguito alla loro analisi, è stato proposto un secondo dispositivo con due reservoir riempiti di metallo che facciano da conduttori termici per sostituire i canali laterali del dispositivo precedente, per aumentare la precisione del gradiente termico applicato.Thermophoresis is a mass transport phenomenon which is gaining attention for its possible application as a particle separation technique based on their dimensions and surface chemical properties.
Recently many separation techniques have been implemented in microscopic devices known as lab-on-a-chips (LOCs). The name is due to their ability to integrate different laboratory tools' functions, and they allow to investigate, thanks to their small dimensions, microscopic systems with effects that would be invisible at a macroscopic scale.
From these facts the project of performing thermophoresis experiments in a microfluidic device has been born.
The devices, produced during this thesis work, have been fabricated using the Femtosecond Laser Irradiation followed by Chemical Etching (FLICE) technique, that consists in irradiating a chip with focused pulsed femtosecond laser light to induce modifications into the substrate and selectively etching the irradiated path in a water-acid solution to dig a microchannel network.
Two different device configurations have been proposed.
The first version of the device presents three parallel channels: the two lateral channels contain flowing water at two different temperatures which induces a uniform thermal gradient in the central one. The central channel contains the sample on which the the thermophoretic effect acts.
The concentration profile of the sample has been studied by means of the optical technique named Differential Dynamic Microscopy, which allows to calculate the sample concentration in the channel with particle sizes lower than the microscope resolution limit by analizyng the field scattered through them. Though several measurements have been performed with this device, it has shown some defetcs.
After the analysis of these defects, a second device configuration has been proposed. The lateral channels have been replaced by two metal-filled reservoirs working as thermal contacts, to obtain a more precise control on the thermal gradient
Three-dimensional direct writing of mechanical and biomedical microdevices by two-photon polymerization
No full textLa tesi riporta diverse applicazioni della tecnica di microfabbricazione mediante laser a femtosecondi detta polimerizzazione a due fotoni, che permette di produrre strutture polimeriche di dimensioni micrometriche. Un nuovo materiale a base di PFPE, altamente idrofobico, è stato utilizzato per ottenere punte da microscopia a forza atomica per nanoindentazione su campioni biologici. La fabbricazione di scaffold per il mantenimento della pluripotenza di cellule staminali esclusivamente tramite stimoli meccanici è stata ingegnerizzata per permettere la produzione su larga scala di queste strutture, allo scopo di studiare a fondo questo meccanismo. Sono state dimostrate la fabbricazione e la rotazione di microrotori, ricoperti di magnetite tramite electroless plating e manipolati simultaneamente e con precisione con un campo magnetico rotante. Inoltre, viene presentato un metodo basato esclusivamente su fabbricazione con laser a femtosecondi per produrre circuiti ottici integrati riconfigurabili.The thesis reports on different applications of the femtosecond laser microfabrication technique called two-photon polymerization, that enables the production of micrometer-sized polymeric structures. A new PFPE-based material, highly hydrophobic, has been used to obtain atomic force microscopy tips for nanoindentation on biological samples. The fabrication of cellular scaffold for the maintenance of pluripotency on stem cells through only mechanical cues has been engineered to allow the production on a large scale of these structures, with the aim of studying thoroughly this mechanism. The fabrication and rotation of microrotors covered with magnetite through electroless plating and simultaneously manipulated with great accuracy with a rotating magnetic field have been demonstrated. Moreover, a femtosecond laser fabrication based method to produce reconfigurable integrated optical circuits is presented.DIPARTIMENTO DI FISICALaser Physics, Photonic devices and applications29RAMPONI, ROBERTATARONI, PAOL
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