Rapid prototyping of 3D Organic Electrochemical Transistors by composite photocurable resin

Rapid Prototyping (RP) promises to induce a revolutionary impact on how the objects can be produced and used in industrial manufacturing as well as in everyday life. Over the time a standard technique as the 3D Stereolithography (SL) has become a fundamental technology for RP and Additive Manufacturing (AM), since it enables the fabrication of the 3D objects from a cost-efective photocurable resin. Eforts to obtain devices more complex than just a mere aesthetic simulacre, have been spent with uncertain results. The multidisciplinary nature of such manufacturing technique furtherly hinders the route to the fabrication of complex devices. A good knowledge of the bases of material science and engineering is required to deal with SL technological, characterization and testing aspects. In this framework, our study aims to reveal a new approach to obtain RP of complex devices, namely Organic Electro-Chemical Transistors (OECTs), by SL technique exploiting a resin composite based on the conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and the photo curable Poly(ethylene glycol) diacrylate (PEGDA). A comprehensive study is presented, starting from the optimization of composite resin and characterization of its electrochemical properties, up to the 3D OECTs printing and testing. Relevant performances in biosensing for dopamine (DA) detection using the 3D OECTs are reported and discussed too

3D Printing with the Commercial UV-Curable Standard Blend Resin: Optimized Process Parameters towards the Fabrication of Tiny Functional Parts

Stereolithography 3D printing is today recognized as an effective rapid prototyping technique in the field of polymeric materials, which represents both the strengths and the weaknesses of this technique. The strengths relate to their easy handling and the low energy required for processing, which allow for the production of structures down to the sub-micrometric scale. The weaknesses are a result of the relatively poor mechanical properties. Unfortunately, the choice of the right material is not sufficient, as the printing parameters also play a crucial role. For this reason, it is important to deepen and clarify the effect of different printing conditions on final product characteristics. In this paper, the behavior of commercial Standard Blend (ST Blend) acrylic resin printed with stereolithography (SL) apparatus is reported, investigating the influence of printing parameters on both the tensile properties of the printed parts and the build accuracy. Twenty-four samples were printed under different printing conditions, then dimensional analyses and tensile tests were performed. It was possible to find out the optimum printing setup to obtain the best result in terms of mechanical resistance and printing accuracy for this kind of resin. Finally, a micrometric spring was printed under the optimal conditions to demonstrate the possibility of printing accurate and tiny parts with the commercial and inexpensive STBlend resin

Design and Characterization of Microfluidic Devices for Water/Oil Separation

Demulsification is the breaking of immiscible fluids into two phases, i.e. removing water in oil or oil in water. It is a fundamental step in oil processing. The main difficulty of demulsification is destabilizing emulsions to a satisfactory level for successive steps. Demulsification techniques can be grouped into three main categories: chemical, biological, and physical treatments. They are often combined to improve destabilization of the emulsions. In this paper we propose a preliminary study for preparing suitable oil samples for analytical investigation, based on a microfluidic approach for water separation from water in oil (WO) emulsions. We also suggest the possibility of using scanning micro-Fourier Transform Infrared Spectroscopy (μ-FTIR) to analyze oil samples containing drops of water of micro-dimensions. A glass/silicon microfluidic device characterized by a snake-like microchannel (200 μm wide and 100 μm high) ending in a Y-junction is proposed. The total volume of the microfluidic device is 3 μl. WO separation is favored by an asymmetric chemical functionalization of the inner surfaces of the microchannel. The surface functionalization process is indeed performed by a wet-chemistry process to make half of the channel hydrophilic, while turning the opposite surface hydrophobic. Taking advantage of the laminar flow spontaneously established inside the microchannel, this approach favors the spontaneous separation of water from oil along the microchannel itself while flowing. Water drops firstly appear at the sidewall of the channels and then they coalesce to form larger drops. Separation of water from oil is obtained at the Y-junction, which is designed to have one branch totally hydrophobic and the other one completely hydrophilic. At the two ends of the microfluidic device two samples can be collected, just oil at the hydrophobic side and a water in oil system at the hydrophobic side, with large water drops. Scanning micro-Fourier Transform Infrared Spectroscopy (μ-FTIR), both in reflectance and transmission modes, was used to analyze WO emulsions. We demonstrated that this analytical technique can be successfully used to characterize WO emulsions if water drop dimensions are in the micrometer range, obtaining signals with no significant noise or disturbance related to the presence of water

A novel highly electrically conductive composite resin for stereolithography

The use of 3D printing for scientific and industrial applications is rapidly increasing and, simultaneously, is growing the interest toward printable smart materials. It is known that using a conductive filler, e.g. nanoparticles, metal powders or composite polymers, it is possible to produce a more electrically conductive printable material. The PEDOT:PSS polymer has been used extensively, from bioelectronics to energy storage devices, for its conductivity and biocompatibility. In this work, a highly electrically conductive resin for Stereolithography was developed using a dispersion of PEDOT particles, extracted from Clevios™ PH1000 through a simple separation process, in a PEGDA matrix. The resin composition was optimized in terms of photoinitiator, surfactant and filler concentration. Furthermore, optimal printing parameters were determined for this composite resin, obtaining a printed object with appreciable electrical conductivity (0.05 S cm−1) and mechanical properties (Young modulus 21 MPa)

Le problème de l'action subrogatoire contre l'État de l'assureur d'un militaire

International audienceNote sous CE, 7 mai 2010, n° 304376, Assurances générales de France (Cie), Philippot, Lebon ; AJDA 2010. 983 ; ibid. 1138, chron. S.-J. Liéber et D. Bottegh