281 research outputs found
Doubly resonant porous silicon microcavities for enhanced detection of fluorescent organic molecules
No full textBeniamino Sciacca, Francesca Frascella, Alberto Venturello, Paola Rivolo, Emiliano Descrovi, Fabrizio Giorgis, Francesco Geobald
Functionalization protocols of silicon micro/nano-mechanical biosensors
No full textFunctionalization is a key element in biodetection technologies such as micro/nano-mechanical sensors. Since assay sensitivity and stability drastically depends on a proper bioreceptor immobilization, the sensing surface must be first chemically modified with uniform, well-packed, and robust layers. Here, we describe three functionalization protocols that we developed for the surface modification with amino, aldehyde, and carboxyl groups of micro/nano-mechanical biosensor
Reversible Shaping of Microwells by Polarized Light Irradiation
No full textIn the last years, stimuli-responsive polymeric materials have attracted great interest, due to their low cost and ease of structuration over large areas combined with the possibility to actively manipulate their properties. In this work, we propose a polymeric pattern of soft-imprinted microwells containing azobenzene molecules. The shape of individual elements of the pattern can be controlled after fabrication by irradiation with properly polarized light. By taking advantage of the light responsivity of the azobenzene compound, we demonstrate the possibility to reversibly modulate a contraction-expansion of wells from an initial round shape to very narrow slits. We also show that the initial shape of the microconcavities can be restored by flipping the polarization by 90°. The possibility to reversibly control the final shape of individual elements of structured surfaces offers the opportunity to engineer surface properties dynamically, thus opening new perspectives for several applications
Ultra-Thin Plasma-Polymerized Functional Coatings for Biosensing: Polyacrylic Acid, Polystyrene and Their Co-Polymer
No full textRecently, many efforts have been done to chemically functionalize sensors surface to achieve selectivity towards diagnostics targets, such as DNA, RNA fragments and protein tumoural biomarkers, through the surface immobilization of the related specific receptor. Especially, some kind of sensors such as microcantilevers (gravimetric sensors) and one-dimensional photonics crystals (optical sensors) able to couple Bloch surface waves are very sensitive. Thus, any kind of surface modifications devoted to functionalize them has to be finely controlled in terms of mass and optical characteristics, such as refractive index, to minimize the perturbation, on the transduced signal, that can affect the response sensitivity towards the detected target species. In this work, the study and optimization of ultra-thin plasma polymers and copolymers, compatible with these constrains and obtained from the vapours of acrylic acid containing a carboxylic (−COOH) group and styrene (an aromatic molecule with a vinyl as substituent at the ring), are reported. The obtained plasma polyacrylic acid (PPAA), plasma polystyrene (PPST) and their copolymer (PPAA-ST), characterized through optical contact angle analysis (OCA), Fourier transform infrared (FTIR) spectroscopy in attenuated total reflection (ATRFTIR), X-ray photoelectrons spectroscopy (XPS), and atomic force microscopy (AFM), are shown to match specific and critical requirements, such as low thickness (∼40 nm) and refractive index (∼1.5), high surface density of reactive groups (1015-1016 COOH/cm2), bioantifouling properties where required, reproducibility, and chemical resistance and stability
Reconfigurable elastomeric graded-index optical elements controlled by light
No full textAbstractIn many optical applications, there is an increasing need for dynamically tunable optical elements that are able to shape the wavefront of light ‘on demand’. In this work, an elastomeric easy-to-fabricate optical element whose transmission functions can be reversibly phase configured by visible light is demonstrated. The light responsivity of proper azopolymers incorporated within an elastomeric matrix is exploited to induce a light-controlled graded refractive index (GRIN) distribution within the bulk compound. The induced refractive index distribution is continuous and conformal to the intensity profile of the illumination at moderate power. A 100 mW doubled-frequency Nd:YAG Gaussian beam focused to a 650 μm waist is shown to induce a maximum relative refractive index change of ~0.4% in the elastomeric matrix, with an approximately parabolic profile. The restoring characteristics of the elastomeric matrix enable full recovery of the initial homogeneous refractive index distribution within a few seconds when the incident laser is switched off. As an exemplary application, the configurable GRIN element is used in a microscope-based imaging system for light control of the effective focal length.</jats:p
A flow-through holed PDMS membrane as a reusable microarray spotter for biomedical assays
No full textWe propose the exploitation of a holed-designed poly(dimethyl)siloxane (PDMS) membrane as an innovative microarray spotter. The membrane is fabricated by a simple technological approach and can be reused several times. A good level of reproducibility is found upon spotting fluorescent proteins at different concentrations over large areas
Light-driven reversible shaping of 2D polymeric lattices
No full textWe propose optically reconfigurable polymeric microstructures. Azopolymer-PMMA composite is pre-structured in micro-pillar array. The reversible shaping of photosensitive structures guided by the polarization state of the incident light is demonstrated
Innovative Detection of Biomarkers Based on Chemiluminescent Nanoparticles and a Lensless Optical Sensor
No full textThe identification and quantification of biomarkers with innovative technologies is an urgent need for the precise diagnosis and follow up of human diseases. Body fluids offer a variety of informative biomarkers, which are traditionally measured with time-consuming and expensive methods. In this context, lateral flow tests (LFTs) represent a rapid and low-cost technology with a sensitivity that is potentially improvable by chemiluminescence biosensing. Here, an LFT based on gold nanoparticles functionalized with antibodies labeled with the enzyme horseradish peroxidase is combined with a lensless biosensor. This biosensor comprises four Silicon Photomultipliers (SiPM) coupled in close proximity to the LFT strip. Microfluidics for liquid handling complete the system. The development and the setup of the biosensor is carefully described and characterized. C-reactive protein was selected as a proof-of-concept biomarker to define the limit of detection, which resulted in about 0.8 pM when gold nanoparticles were used. The rapid readout (less than 5 min) and the absence of sample preparation make this biosensor promising for the direct and fast detection of human biomarkers
Laser-induced anisotropic wettability on azopolymeric micro-structures
No full textThe light-induced deformation of a micro-textured photo-sensitive polymeric material is exploited for modifying the surface hydrophobicity along deterministic directions. Arrays of azopolymeric micro-pillars are fabricated over large area and irradiated with a green laser. Upon laser irradiation, the micro-pillars deform reversibly along a direction parallel to the laser polarization, resulting in elongated shapes with controllable eccentricity. Such a locally anisotropic topography induces a directional yet reversible change of hydrophobicity, as measured by contact angles varying within a range of 30 degrees. Published by AIP Publishing
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