S Coppola

INO - Istituto Nazionale di Ottica, Florens, Tuscany, Italy

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Publications (96)251.45 Total impact

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    ABSTRACT: Electrical conductivity and viscosity play a major role in the tip jetting behaviour of liquids subjected to electrohydrodynamic (EHD) forces, thus influencing significantly the printing performance. Recently, we developed a nozzle- and electrode-free pyro-EHD system as a versatile alternative to conventional EHD configurations and we demonstrated different applications, including inkjet printing and three-dimensional lithography. However, only dielectric fluids have been used in all of those applications. Here, we present an experimental characterization of the pyro-EHD jetting regimes, induced by laser blasts, of sessile drops in case of dielectric and conductive liquids in order to extend the applicability of the system to a wider variety of fields including biochemistry and biotechnology where conductive aqueous solutions are typically used.
    Applied Physics Letters 01/2015; 106(5):054103. DOI:10.1063/1.4907005 · 3.52 Impact Factor
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    ABSTRACT: A novel scheme for solar energy harvesting based on the pyro-electric effect has been demonstrated. The proposed harvester is based on an optical system focusing solar radiation onto a ferroelectric crystal (i.e. lithium niobate). The face exposed to the heating source is coated with a nanocomposite material (i.e. carbon black and graphene particles) that greatly improves the adsorption of solar radiation. The solar energy focused onto the crystal through a simple optical system allows one to induce a thermal gradient able to generate electric charges. Experiments have been carried out indoor as well as outdoor (in Pozzuoli, Naples, Italy, on December). Results show that two configurations appear to be preferable: (a) pyro-electric element with carbon black-based coating and a Fresnel lens (surface of about 100 cm2); (b) pyro-electric element with graphene-based coating and a Fresnel lens (surface of about 600 cm2). In both experimental arrangements the maximum temperature variation reached locally onto the lithium niobate substrate is relatively high with peaks greater than 250 °C. The maximum electrical power peak is of about 90 μW and about 50 μW for (a) and (b) respectively. The results of this first investigation are encouraging for further development of more efficient harvesting devices.
    Applied Energy 12/2014; 136:357-362. DOI:10.1016/j.apenergy.2014.09.035 · 5.26 Impact Factor
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    ABSTRACT: 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.
    Nature Communications 11/2014; 5. DOI:10.1038/ncomms6314 · 10.74 Impact Factor
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    ABSTRACT: In this work we introduce an easy multiscale approach for the fabrication of polymer microlens arrays through a self-assembling process driven by the electrohydrodynamic (EHD) pressure. This method represents a simple alternative to the conventional soft lithography techniques. A thin layer of liquid polymer is deposited on a micro-engineered ferroelectric crystal and can be self-assembled and cross-linked in a single step process as a consequence of the pyro-electric effect activated by simply heating the substrate. Although the EHD instability induced by the pyroelectric effect was discovered in principle few years ago, here we demonstrate a systematic investigation for fabrication of microlens arrays in a multiscale range (i.e. between 25 ???m to 200 ???m diameter) with high degree of uniformity. By controlling the polymer instability driven by EHD, we report on two different micro-optical shapes can be obtained spontaneously, i.e. spherical or toroidal. Here we show how the geometrical properties and the focal length of the lens array are modulated by controlling two appropriate parameters. Such microlenses can be useful also as polymer patterned arrayed microstructures for optical data interconnections, OLEDs efficient light extraction, concentrating light in energy solar cells, imaging and 3D display solutions and other photonics applications.
    IEEE Journal of Selected Topics in Quantum Electronics 11/2014; DOI:10.1109/JSTQE.2014.2367656 · 3.47 Impact Factor
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    ABSTRACT: Here, we report on a single step approach for fabricating free-standing polymer membranes reinforced with arrayed self-assembled carbon nanotubes (CNTs). The CNTs are self-assembled spontaneously by electrode-free DC dielectrophoresis based on surface charge templates. The electrical charge template is generated through the pyroelectric effect onto periodically poled lithium niobate ferroelectric crystals. A thermal stimulus enables simultaneously the self-assembly of the CNTs and the cross-linking of the host polymer. Examples of thin polydimethylsiloxane membranes reinforced with CNT patterns are shown.
    Applied Physics Letters 10/2014; 105(15):153101. DOI:10.1063/1.4898206 · 3.52 Impact Factor
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    ABSTRACT: A lthough electrospinning (ES) allows the production of unsurpassed nanoscale polymer fibers, the major draw-backs are the nozzle-clogging and single-jet spinneret, respectively. This is a real limitation in terms of usable polymers and for patterning active organics. Nowadays the micro-engineering of smart materials could represent a new route for many fields of technology ranging from the production of electronic and photonic devices 1−3 to regener-ative medicine and tissue engineering. 4−7 An enormous technological interest is related to the possibility of patterning fibers directly in well-ordered patterns avoiding the deposition of nonwoven submicrometer mats often occurring in ES. 8,9 In the past decade several attempts have been made using field-induced 10−13 and near-field ES, 14,15 but only very recently, with the introduction of mechano ES, 16 has the production of well-ordered fiber patterns been achieved. Nevertheless, some drawbacks related to the complexity of the setup, the operating temperature, and the selection of usable materials for problems related to nozzle clogging still persist. Moreover, high temperature can cause deterioration of the optical and electronic properties of active organic materials eventually embedded in the functionalized fibers. On the other side, interfering effects due to closeness of multiple electrified nozzles ban working with multiple spinnerets. Here we introduce a revolutionary nozzle-free approach, the tethered pyro-electrodynamic spinning (TPES) operating in wireless modality, i.e., without electric circuit, electrodes, and voltage supply. This novel approach definitively simplifies the ES apparatus extending the nanofiber spinning also to active organic polymers preserving at the same time all the properties of conventional systems. Fiber drawing from the liquid polymer is driven through the pyroelectric charge generated into a ferroelectric crystal (i.e., LiNbO 3) able to induce the electro-hydrodynamics (EHD) pressure required for polymer manip-ulation without wires. The approach is highly flexible, simple, compact, and cost-effective when compared with classical ES, and last but not least, it allows working safely, avoiding the use of high-voltage equipment at kVolts scale. For the first time, in situ observation of fiber drawing is provided allowing real-time adjustments and full control of the process. Moreover the TPES adds to the capabilities of conventional ES the chance of printing polymer fibers even in the case of multiple drops opening the way to the multijetting spinneret modality for multiplexing and speeding up the fabrication process. Printing of micro-and nanofibers directly from a polymer drop with unprecedented order, direct writing of sharp/straight edges, and easy multijets electrospinning are demonstrated and reported. Experimental fabrication of patterns embedded with active molecules ensures that functionalized patterns preserve their functionalities after the TPES process. Results regarding the use of smart patterns for keeping alive and viable cultured cells are discussed. This study opens the way to innovative optogenesys analysis, guiding light for generating or trans-porting optical/electronic signals from and to cells. 17−21 The setup proposed in this work, unlike the conventional ES, is electrode-free and nozzle-free, Figure 1a,b. The method allows polymer nanofibers to be printed directly from a polymer drop overpassing the viscosity border of nozzle clogging in conventional inkjet systems. 22 The drop reservoir is placed directly on a flat substrate (base) while an electric field,
    Chemistry of Materials 06/2014; DOI:10.1021/cm501265j · 8.54 Impact Factor
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    ABSTRACT: Hypodermic needle injection is still the most common method of drug delivery despite its numerous limitations and drawbacks, such as pain, one-shot administration, and risk of infection. Seeking a viable, safe, and pain-free alternative to the over 16 billion injections per year has therefore become a top priority for our modern technological society. Here, a system that uses a pyroelectric cartridge in lieu of the syringe piston as a potential solution is discussed. Upon stimulation, the cartridge electro-draws, at room temperature, an array of drug-encapsulated, biodegradable polymer microneedles, able to deliver into hypodermic tissue both hydrophobic and hydrophilic bioactive agents, according to a predefined chrono-programme. This mould-free and contact-free method permits the fabrication of biodegradable polymer microneedles into a ready-to-use configuration. In fact, they are formed on a flexible substrate/holder by drawing them directly from drop reservoirs, using a controlled electro-hydrodynamic force. Tests of insertion are performed and discussed in order to demonstrate the possibility to prepare microneedles with suitable geometric and mechanical properties using this method.
    Advanced Functional Materials 06/2014; 24(23). DOI:10.1002/adfm.201303679 · 10.44 Impact Factor
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    ABSTRACT: In the case of light emitting semiconducting polymers, different techniques have been used for the fabrication of electroluminescent devices. Experiments and characterizations have been carried out at different operating voltages and for voltage dependent emission color also combining the processability of organic materials with efficient luminescence displayed by inorganic nanocrystals (NCs). In fact, the experimental perspective to disperse emitting colloidal NCs into polymers has allowed to further engineer hybrid organic-inorganic materials introducing innovative functionalities as for instance photoluminescence conversion capabilities. This has proved of great interest for novel applications such as the fabrication of photonic crystals and, notably, of innovative solar cells showing enhanced efficiency. Here we report on the fabrication of novel active micro-optical elements made by a mixture of rod-shaped inorganic NCs dispersed into poly-dimethylsiloxane.
    Proc. SPIE 9130, Micro-Optics 2014, 91300Q, Brussels, Belgium; 05/2014
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    ABSTRACT: In the recent years many commercial applications such as optoelectronics, photonic and biomedical devices, as well as image processing require the fabrication of adaptive and adjustable micro-lens array. A lot of attempts have been conducted in order to support the growing interest in the production of lens arrays for sensors or optical communications devices for parallel data transmission. Several fabrication techniques and a large variety of process have been proposed for polymer based microlenses and their incorporation into technological devices with a large area of application, but, the preparation of moulds, masks or metal layers with very accurate dimensions and shapes is generally required. Here we present the application of a pyro-electrohydrodynamic (Pyro-EHD)-dispenser for the fabrication of polymer microlens arrays overpassing the viscosity limit of the conventional ink-jet printing systems and working in a nozzle-less modality. The results regarding the fabrication procedure and the characterization of polymer micro-lens arrays of different shapes and heights are examined.
    SPIE Photonics Europe; 05/2014
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    ABSTRACT: In this work we present a direct printing of microlenses using high viscous polymer materials. In particular the pyro-electric effect activated onto a Lithium Niobate crystal is exploited for the fabrication on demand of microlens array.
    2014 Fotonica AEIT Italian Conference on Photonics Technologies (Fotonica AEIT); 05/2014
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    ABSTRACT: Novel and intriguing lithographic approaches based on instabilities of liquid polymers and electro-hydro-dynamic at nanoscale have been developed. The unusual fabrication methods were aimed at fabricating 3D polymeric microstructures. A variety of microstructures were fabricated and tested for applications in different fields 1. LIQUID NANO DISPENSER A new opto-nanofluidic approach named Pyro-EHD is presented for dispensing liquid nano-pico-droplets through pyroelectric effect activated by hot tip source or an IR laser into a dielectric crystal using a non-invasive simple and powerful electrode-less configuration. The manipulation of small amounts of liquids at micro to nanometer scale is of great interest in many fields of technology: biotechnology, patterning by deposition of inorganic, organic and biological inks and photnics [1-4]. We show a new and simple system where the liquid actuation and dispensing has been achieved through electrode-less configurations using polar dielectric crystals such as Lithium Niobate (LN) crystal and by exploiting the pyroelectric effect [5,6]. The technique presented allows one to avoid the use of high-voltage power supplies and electrical circuits, and moreover there is no need to design and fabricate nanocapillary nozzles. The functionalization of the lithium niobate (LN) is obtained by micro-engineering the ferroelectric domains and by inducing the pyroelectric effect through the use of appropriate heat sources such as a IR laser beam [7]. The set-up consists basically of a polished 500-µm thick z-cut LN substrate (from Crystal Technology, Inc.) placed over a microscope glass slide at a specific distance fixed by appropriate spacers (Figure 1). A liquid drop or film is first deposited on the glass slide and successively the upper surface of the LN wafer is placed in contact with an heated-tip that can be scanned in order to induce point-wise thermal stimuli. The heated-tip is in axis with the droplet reservoir on the microscope glass slide. A conventional heated soldering tip was used as heated-tip-source. LN reacts to the thermal-stimuli by building-up an electric potential across the z-cut LN crystal's surfaces because of the pyroelectric effect, that consists in the spontaneous polarization change ∆Ps following to a temperature gradient ∆T. At equilibrium, the crystal Ps is fully screened by the external screening charge and no electric field exists [8]. When the heating source locally heats the crystal, a sudden surface charge density σ immediately appears given by neglecting losses, where Pc is the material-specific pyroelectric coefficient (Pc= -8.3 x 10 -5C/°C/m2 for LN @ 25°C). The electric field exerts an attractive force on the liquid . When the liquid starts to deform under the action of the electric field, two evolutions are possible. Case (I): if the liquid volume and the separation distance D between the two Invited Paper
    Proc. SPIE 8982, Optical Components and Materials XI, 89820N (March 7, 2014), San Francisco; 03/2014
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    ABSTRACT: Carbon nanoparticles are becoming ubiquitous in many fields of science and technology. However, a grand challenge remains in assembling, patterning, and positioning or even simple manipulation of CNTs for complex functional assemblies. CNTs have in fact enormous perspectives for application in biotechnologies as bactericide agents or as prominent tools for investigating cell mechanisms, or more in general as functionalized nanoparticle-vectors, but their exploitation requires viable technology at the lab-on-a-chip scale. Many approaches have been attempted in developing technologies for manipulating CNTs. One elective approach is based on electric fields driven mechanisms such as DEP forces. A variety of chips have been designed and realized with this aim. Here we report on a novel hybrid microfluidic chip made by assembling a polar-dielectric crystal with polymeric microfluidic channels. One challenging feature of such a hybrid device approach, based on an electrode-free dielectrophoretic (DEP) approach, is that it makes use of surface charge templates for self-assembling and manipulation of CNTs in liquid media directly into a microfluidic channel. Here various examples of self-assembly in microfluidic channels as well as separation and collection of two classes of nano/microparticles are reported. The method can open the way to novel fabrication protocols for the realisation of future flexible devices with new and more complex functionalities, highly desirable in electronics as well as in biotechnology at the lab-on-a-chip scale.
    RSC Advances 01/2014; 4(6):2851. DOI:10.1039/c3ra45698f · 3.71 Impact Factor
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    ABSTRACT: 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.
    Langmuir 12/2013; 29(50). DOI:10.1021/la403603d · 4.38 Impact Factor
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    ABSTRACT: In the present work, the pyro-electrohydrodynamic technique was used for the realization of tunable-size microlens arrays. Poly(methyl methacrylate) dissolved in different solvent mixtures was used as the polymeric material for the realization of the microstructures. By controlling the experimental parameters and in particular, the volume of the drop reservoir, graded-size square arrays of tens of microlenses with focal length in the range 1.5-3 mm were produced. Moreover, the optical quality and geometrical features were investigated by profilometric and interferometric analysis.
    Applied Optics 11/2013; 52(32):7699-705. DOI:10.1364/AO.52.007699 · 1.78 Impact Factor
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    ABSTRACT: We present a laser-assisted system for dispensing liquid micro-droplets by near infrared illumination of a pyroelectric crystal functionalized with gold nanorods embedded into polyvinyl alcohol. The non-invasive near infrared source resonates with the plasmon oscillations of the gold nanorods, providing a controlled thermal stimulus able to generate the pyroelectric effect. The resulting electric field interacts electro-hydrodynamically with a liquid reservoir leading to precise drawing of micro-litre droplets. This laser-assisted electro-hydrodynamic technique may open the way to the development of more compact and non-invasive nano-dispensing devices. (C) 2013 AIP Publishing LLC.
    Applied Physics Letters 10/2013; 103(16). DOI:10.1063/1.4825337] · 3.52 Impact Factor
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    ABSTRACT: Pyroelectric effect of ferroelectric crystals has been recently employed to align carbon-based nanoparticles into long wires, embedded in different polymer matrices. In fact, it is observed that the carbon-based Nano particles self-assemble along the electrical field lines, generated through spontaneous charge templates arising pyro electrically onto ferroelectric crystals. In order to control the pyroelectric effect to assure a repeatable assembling, we fabricate a micro-heater on one side of the ferroelectric crystal surface and deposit aluminium triangular tips on the other side. Application of a short heat pulse through micro-heater produces spontaneous electron charge on the other side of ferroelectric crystal surface causing the carbon Nano particle assembling along the flow of electron charges between aluminium tips. Several simulations have been carried out to evaluate the dependence of both the micro-heater and aluminium tips shape on the pyroelectric effect.
    5th EOS Topical Meeting on Optical Microsystems (OμS’13); 1st EOS Topical Meeting on Optics at the Nanoscale (ONS’13, Capri italy; 09/2013
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    ABSTRACT: Very interesting effects can be observed in maneuvering nematic liquid crystal (NLC) droplets onto functionalized polar lithium niobate (LN) crystal surfaces, covered with thin films of Polydimethylsiloxane (PDMS). It has been discovered that pyroelectric effect is able to drive a reversible fragmentation process in liquid crystal drops, starting from nanoliter drops and obtaining pico/femtoliter droplets. These small droplets are patterned according to the geometry of the substrate and aligned along the electric field lines. This novel approach for manipulating different classes of liquids by exploiting the pyroelectric effect, where the strong electric fields generated allow to manipulate liquids in 2D on a substrate or even in 3D, has been recently discovered and exploited for different purposes. In particular, manipulation of liquid crystals by a thermal stimulus could be suitable for applications such as spatial modulation of the wettability (i.e. wettability patterning), or, in principle, a dynamical optical element able to switch from a diffuser (fragmentation) state to a microlens array. Moreover, the biocompatibility of some kinds of nematic or cholesteric liquid crystals makes them suitable as biomaterials for applications in biology and tissue engineering.
    SPIE Optical Metrology 2013; 05/2013

Publication Stats

1k Citations
251.45 Total Impact Points

Institutions

  • 2009–2014
    • INO - Istituto Nazionale di Ottica
      Florens, Tuscany, Italy
  • 1992–2014
    • University of Naples Federico II
      • • Department of Chemical, Materials and Industrial Production Engineering
      • • Department of Physical Sciences
      • • Department of Agriculture
      Napoli, Campania, Italy
  • 2011–2013
    • National Research Council
      • Institute for Microelectronics and Microsystems IMM
      Oristany, Sardinia, Italy