arXiv subjects

Francesco Greco

Publications and source records attributed to Francesco Greco.

22 records · Page 2Linked to original sources

arXiv2018

Ultra-Conformable Free-Standing Capacitors Based on Ultrathin Polyvinyl Formal Films

Conformable Electronics refers to a class of electronic devices that have the ability to conformally adhere onto non-planar surfaces and materials, resulting particularly appealing for skin applications, such as the case of skin-worn unobtrusive (bio)sensors for healthcare monitoring. Conformability can be addressed by integrating basic electronic components on ultrathin polymeric film substrates. Among other basic electronic components, capacitors are fundamental ones for energy storage, sensing, frequency tuning, impedance adaptation and signal processing. In this work we present a novel approach for conformable capacitors based on a free-standing, ultrathin and ultra-conformable nanosheets of poly (vinyl formal) (PVF), which serve both as structural and dielectric component of the capacitor. A novel fabrication approach is proposed and applied to fully free-standing ultrathin capacitors fabrication, having an overall thickness as low as 200 nm; that represents, to the best of our knowledge, the thinnest free-standing capacitors ever reported. Thanks to the ultra-low thickness, the proposed capacitors are able to sustain flexure to extremely small curvature radii (as low as 1.5 μm) and to conform to complex surfaces, such as a nylon mesh with micrometric texture without compromising their operation.

physics.app-ph↗

arXiv2018

Tattoo-Paper Transfer as a Versatile Platform for All-Printed Organic Edible Electronics

The use of natural or bioinspired materials to develop edible electronic devices is a potentially disruptive technology that can boost point-of-care testing. The technology exploits devices which can be safely ingested, along with pills or even food, and operated from within the gastrointestinal tract. Ingestible electronics could potentially target a significant number of biomedical applications, both as therapeutic and diagnostic tool, and this technology may also impact the food industry, by providing ingestible or food-compatible electronic tags that can smart track goods and monitor their quality along the distribution chain. We hereby propose temporary tattoo-paper as a simple and versatile platform for the integration of electronics onto food and pharmaceutical capsules. In particular, we demonstrate the fabrication of all-printed Organic Field-Effect Transistors (OFETs) on untreated commercial tattoo-paper, and their subsequent transfer and operation on edible substrates with a complex non-planar geometry.

physics.app-ph↗

arXiv2014

Microrheology with Optical Tweezers: Measuring the solutions' relative viscosity at a glance

We present a straightforward method for measuring the fluids' relative viscosity via a simple graphical analysis of the normalised position autocorrelation function of an optically trapped bead, without the need of embarking on laborious calculations. The advantages of the proposed microrheology method become evident, for instance, when it is adopted for measuring the molecular weight of rare or precious materials by means of their intrinsic viscosity. The proposed method has been validated by direct comparison with conventional bulk rheology methods.

physics.flu-dyn↗

arXiv2006

Mechanical Properties of End-crosslinked Entangled Polymer Networks using Sliplink Brownian Dynamics Simulations

The mechanical properties of a polymeric network containing both crosslinks and sliplinks (entanglements) are studied using a multi-chain Brownian dynamics simulation. We coarse-grain at the level of chain segments connecting consecutive nodes (cross- or sliplinks), with particular attention to the Gaussian statistics of the network. Affine displacement of nodes is not imposed: their displacement as well as sliding of monomers through sliplinks is governed by force balances. The simulation results of stress in uniaxial extension and the full stress tensor in simple shear including the (non-zero) second normal stress difference are presented for monodisperse chains with up to 18 entanglements between two crosslinks. The cases of two different force laws of the subchains (Gaussian chains and chains with finite extensibility) for two different numbers of monomers in a subchain (no = 50 and no = 100) are examined. It is shown that the additivity assumption of slip- and crosslink contribution holds for sufficiently long chains with two or more entanglements, and that it can be used to construct the strain response of a network of infinitely long chains. An important consequence is that the contribution of sliplinks to the small-strain shear modulus is about ⅔ of the contribution of a crosslink.

cond-mat.soft↗