We tackle the problem of information recovery and imaging through scattering microfluidic chips by means of digital holography (DH). In many cases the chip can become opalescent due to residual ...deposits settling down the inner channel faces, biofilm formation, scattering particle uptake by the channel cladding or its damaging by corrosive substances, or even by condensing effect on the exterior channels walls. In these cases white-light imaging is severely degraded and no information is obtainable at all about the flowing samples. Here we investigate the problem of counting and estimating velocity of cells flowing inside a scattering chip. Moreover we propose and test a method based on the recording of multiple digital holograms to retrieve improved phase-contrast images despite the strong scattering effect. This method helps, thanks to DH, to recover information which, otherwise, would be completely lost.
Highly sensitive detection of biomolecules is of paramount interest in many fields including biomedicine, safety and eco-pollution. Conventional analyses use well-established techniques with ...detection limits ~1 pM. Here we propose a pyro-concentrator able to accumulate biomolecules directly onto a conventional binding surface. The operation principle is relatively simple but very effective. Tiny droplets are drawn pyro-electro-dynamically and released onto a specific site, thus increasing the sensitivity. The reliability of the technique is demonstrated in case of labelled oligonucleotides diluted serially. The results show the possibility to detect very diluted oligonucleotides, down to a few hundreds of attomoles. Excellent results are shown also in case of a sample of clinical interest, the gliadin, where a 60-fold improved detection limit is reached, compared with standard ELISA. This method could open the way to a mass-based technology for sensing molecules at very low concentrations, in environmental as well as in diagnostics applications.
Electrohydrodynamic jetting is emerging as a successful technique for printing inks with resolutions well beyond those offered by conventional inkjet printers. However, the variety of printable inks ...is still limited to those with relatively low viscosities (typically <20 mPa s) due to nozzle clogging problems. Here, we show the possibility of printing ordered microdots of high viscous inks such as poly(lactic-co-glycolic acid) (PLGA) by exploiting the spontaneous breakup of a thin fiber generated through nozzle-free pyro-electrospinning. The PLGA fiber is deposited onto a partially wetting surface, and the breakup is achieved simply by applying an appropriate thermal stimulation, which is able to induce polymer melting and hence a mechanism of surface area minimization due to the Plateau–Rayleigh instability. The results show that this technique is a good candidate for extending the printability at the microscale to high viscous inks, thus extending their applicability to additional applications, such as cell behavior under controlled morphological constraints.
Spiral shapes occur frequently in nature as in the case of snail shells or the cochlea - the auditory portion of the inner ear. They also inspire many technological devices that take advantage of ...this geometry. Here we show that μ-pyro-electrospinning is able to control whipping instabilities in order to form spiralling fibres (down to 300 nm thick) directly on a support with true microscale regularity. The results show that polymer concentration plays a key role in producing reliable and long spirals. We investigate the cell response to these spiral templates that, thanks to their true regularity, would be useful for developing innovative cochlea regeneration scaffolds.
The unique deformability and the compliance ability of thin sheets on soft substrates attract much interest for studying the phenomena related to elastic instabilities as well as for sensing very ...weak forces such as those generated by live cells in vitro. However, the techniques used currently for producing such platforms are affected by a high degree of complexity and poor repeatability. Moreover, their deformability is usually used as a passive response to the action of an external force. Herein we propose a novel concept for a reliable and dynamic skin-over-liquid system made of a periodic array of highly compliant microbumps actuated through electrode-free electrohydrodynamic (EHD) pressure. We demonstrate that these structures are highly repeatable and capable of swelling and deflating easily under a simple thermal stimulation driven by the pyroelectric effect, thus providing a challenging platform that can be actively controlled at the microscale. Furthermore, we show the proof of principle by swelling these microbumps for mechanically stimulating live cells in vitro, thus opening the route to more reliable and easy to accomplish assays in the field of mechanobiology.Biomechanics: Giving artificial skin the goosebumpsResearchers curious about how mechanical stress impacts cell growth can now turn to silicone plastics that grow microbumps on demand. Simonetta Grilli from Italy’s Institute of Applied Sciences and Intelligent Systems in Pozzuoli and colleagues created a controllable ‘skin-over-liquid’ system by coating a silicone polymer solution onto lithium niobate, a crystal that contains patterned regions of electric charge. An initial plasma treatment produced a flat stiff film on top of the liquid silicone. Thermal heating caused the skin to swell and form dimpled, air mattress-like patterns, corresponding to the underlying lithium niobate domains. Removal of heat restored the sheet to its initial state. The chemically inert skin supported live fibroblast cells and was used to determine reactions to mechanical stress. Significant variations in nuclei and cytoskeletons were observed between cells grown under flat or swollen-skin conditions.
•We presented a deep investigation of the pyroelectric effect induced into ferroelectric LN by micro-heater structures integrated directly onto the surface of the crystals. Four configurations were ...considered in order to fully understand the distribution of the electric field under different stimulation conditions.•The effect of the micro-heater shape on the temperature distribution and consequently on the pyroelectric effect was evaluated using COMSOL™ Multiphysics. Simulations were validated by different experimental measurements.•In particular, the pyroelectric effect activated by the micro-heater was investigated analysing the current impulses detected using a micrometric metallic probe connected to an oscilloscope.•Finally, the high repeatability of the pyroelectric effect induced by the integrated micro-heater was demonstrated reporting the occurrence of the impulses.•The reported results let us to claim that by regulating the rate of heating or cooling of the different design of micro-heaters, the occurrence of the pyroelectric effect from the –Z surface of the LiNbO3 can be manipulated and/or controlled is an easy and efficient manner compared with traditional ways of thermalizing the crystal.
We present a deep investigation of pyroelectric fields generated by lithium niobate crystals through integrated microheater structures. The microheaters are made of highly compact titanium microcircuits able to dissipate heat through a low-power consuming Joule effect. Microheaters with diverse geometries were designed and fabricated on the +Z face of lithium niobate crystals, in order to characterize pyroelectric fields with different distributions. The pyroelectric effect was studied under ambient conditions analysing the current impulses detected using a metallic probe connected to an oscilloscope. The current impulses were related to the air breakdown induced by the electric field arising between the −Z face of the crystal and the metallic tip. We show that the fabrication technique is relatively easy to accomplish and we analyse the thermal behaviour of the microheaters both theoretically and experimentally. The results show how such microheaters are able to control the intensity and the spatial distribution of the pyroelectric fields at microscale.
Biofilms are detrimental to human life and industrial processes due to potential infections, contaminations, and deterioration. Therefore, the evaluation of microbial capability to form biofilms is ...of fundamental importance for assessing how different environmental factors may affect their vitality. Nowadays, the approaches used for biofilm evaluation are still poor in reliability and rapidity and often provide contradictory results. Here, we present what we call biofilm electrostatic test (BET) as a simple, rapid, and highly reproducible tool for evaluating in vitro the ability of bacteria to form biofilms through electrostatic interaction with a pyroelectrified carrier. The results show how the BET is able to produce viable biofilms with a density 6-fold higher than that on the control, after just 2 h incubation. The BET could pave the way to a rapid standardization of the evaluation of bacterial resistance among biofilm-producing microorganisms. In fact, due to its simplicity and cost-effectiveness, it is well suited for a rapid and easy implementation in a microbiology laboratory.
Stable chains of carbon-based nanoparticles were formed directly in polymer matrixes through an electrode-free approach. Spontaneous surface charges were generated pyroelectrically onto ...functionalized ferroelectric crystals, enabling the formation of electric field gradients that triggered the dipole–dipole interactions responsible for the alignment of the particles, while embedded in the polymer solution. The phenomenon is similar to the dielectrophoretic alignment of carbon nanotubes reported in the literature. However, here the electric fields are generated spontaneously by a simple heat treatment that, simultaneously, aligns the particles and provides the energy necessary for curing the host polymer. The result is a polymer sheet reinforced with well-aligned chains of carbon-based particles, avoiding the invasive implementation of appropriate electrodes and circuits. Because polymers with anisotropic features are of great interest for enhancing the thermal and/or the electrical conductivity, the electrode-free nature of this technique would improve the scaling down and the versatility of those interconnections that find applications in many fields, such as electronics, sensors, and biomedicine. Theoretical simulations of the interactions between the particles and the charge templates were implemented and appear in good agreement with the experimental results. The chain formation was characterized by controlling different parameters, including surface charge configuration, particle concentration, and polymer viscosity, thus demonstrating the reliability of the technique. Moreover, micro-Raman spectroscopy and scanning electron microscopy were used for a thorough inspection of the assembled chains.
Spiral shapes occur frequently in nature as in the case of snail shells or the cochlea - the auditory portion of the inner ear. They also inspire many technological devices that take advantage of ...this geometry. Here we show that μ-pyro-electrospinning is able to control whipping instabilities in order to form spiralling fibres (down to 300 nm thick) directly on a support with true microscale regularity. The results show that polymer concentration plays a key role in producing reliable and long spirals. We investigate the cell response to these spiral templates that, thanks to their true regularity, would be useful for developing innovative cochlea regeneration scaffolds.
Spiral shapes occur frequently in nature as in case of snail shells or cochlea of the inner ear.
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