Abstract
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-effective photocurable resin. Efforts 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.
In biosensing applications, the exploitation of organic transistors gated via a liquid electrolyte has increased in the last years thanks to their enormous advantages in terms of sensitivity, low ...cost and power consumption. However, a practical aspect limiting the use of these devices in real applications is the contamination of the organic material, which represents an obstacle for the realization of a portable sensing platform based on electrolyte-gated organic transistors (EGOTs). In this work, a novel contamination-free microfluidic platform allowing differential measurements is presented and validated through finite element modeling simulations. The proposed design allows the exposure of the sensing electrode without contaminating the EGOT device during the whole sensing tests protocol. Furthermore, the platform is exploited to perform the detection of bovine serum albumin (BSA) as a validation test for the introduced differential protocol, demonstrating the capability to detect BSA at 1 pM concentration. The lack of contamination and the differential measurements provided in this work can be the first steps towards the realization of a reliable EGOT-based portable sensing instrument.
In several biomedical applications, the detection of biomarkers demands high sensitivity, selectivity and easy-to-use devices. Organic electrochemical transistors (OECTs) represent a promising class ...of devices combining a minimal invasiveness and good signal transduction. However, OECTs lack of intrinsic selectivity that should be implemented by specific approaches to make them well suitable for biomedical applications. Here, we report on a biosensor in which selectivity and a high sensitivity are achieved by interfacing, in an OECT architecture, a novel gate electrode based on aptamers, Au nanoparticles and graphene hierarchically organized to optimize the final response. The fabricated biosensor performs state of the art limit of detection monitoring biomolecules, such as thrombin-with a limit of detection in the picomolar range (≤ 5 pM) and a very good selectivity even in presence of supraphysiological concentrations of Bovine Serum Albumin (BSA-1mM). These accomplishments are the final result of the gate hierarchic structure that reduces sterich indrance that could contrast the recognition events and minimizes false positive, because of the low affinity of graphene towards the physiological environment. Since our approach can be easily applied to a large variety of different biomarkers, we envisage a relevant potential for a large series of different biomedical applications.
In-liquid biosensing is the new frontier of health and environment monitoring. A growing number of analytes and biomarkers of interest correlated to different diseases have been found, and the ...miniaturized devices belonging to the class of biosensors represent an accurate and cost-effective solution to obtaining their recognition. In this study, we investigate the effect of the solvent and of the substrate modification on thin films of organic semiconductor Poly(3-hexylthiophene) (P3HT) in order to improve the stability and electrical properties of an Electrolyte Gated Organic Field Effect Transistor (EGOFET) biosensor. The studied surface is the relevant interface between the P3HT and the electrolyte acting as gate dielectric for in-liquid detection of an analyte. Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) characterizations were employed to study the effect of two solvents (toluene and 1,2-dichlorobenzene) and of a commercial adhesion promoter (Ti Prime) on the morphological structure and electronic properties of P3HT film. Combining the results from these surface characterizations with electrical measurements, we investigate the changes on the EGOFET performances and stability in deionized (DI) water with an Ag/AgCl gate electrode.
Problem statement: Nanotech applications in the oil industry are not completely new: nanoparticles have been successfully used in drilling muds for the past 50 years. Only recently all the other key ...areas of the oil industry, such as exploration, primary and assisted production, monitoring, refining and distribution, are approaching nanotechnologies as the potential Philosopher's stone for facing critical issues related to remote locations (such as ultra-deep water and artic environments), harsh conditions (high-temperature and high-pressure formations), nonconventional reservoirs (heavy oils, tight gas, tar sands). The general aim is to bridge the gap between the oil industry and nanotechnology community using various initiatives such as consortia between oil and service companies and nanotechnology excellence centres, networking communities, workshops and conferences and even dedicated research units inside some oil companies. Quite surprisingly, even if a lot of discussion is taking place, no substantial research on these topics is currently being undertaken around the world by the petroleum industry. A very different attitude is demonstrated by other industries and the advances they achieved are outstanding. Approach: This study provides an overview of the most interesting nanotechnology applications and critically highlights the potential benefits that could come from transposing the same-or adapted-solutions to the oil industry. Results/Conclusion: As extensively illustrated, some technologies which are already available off-the-shelf can offer real improvements in dealing with some specific issues of the oil industry. Other technologies can require further elaboration before direct use, but their potential is enormous.
Stretchable plasmonic nanostructures constituted by Ag nanoparticles on flexible elastomeric matrices are synthesized and used as surface-enhanced Raman scattering (SERS) substrates. The structure ...consists of silver particles deposited by DC sputtering on polydimethylsiloxane (PDMS). The optical transmittance spectra show marked dips related to plasmonic inter-particle short-range interactions. The substrates show noticeable Raman enhancement allowing detection of R6G at very low concentration. Under mechanically controlled stretching, the interparticle gap sizes change yielding a reversible spectral shift of the plasmonic resonance. Experimental results are validated by 3D modeling. When such a resonance matches the Raman excitation line, pronounced enhancements can be achieved, optimizing the SERS regime. Taking advantage of the PDMS matrices, these tunable SERS-active substrates are integrated in microfluidic circuitry fruitfully exploitable for on-chip label-free detection.
Organic electronics has recently emerged as a promising candidate for the emulation of brain‐like functionalities, especially at the device level. Among the proposed technologies, memristive devices ...have gained an increasing attention due to their non‐volatile behavior which makes them suitable for the implementation of artificial neuronal networks. However, most of them have an energy‐costly switching mechanism which limits the approach of brain like energy efficiency. Different from them, organic memristive devices (OMDs) have a narrow switching window and implement neuromorphic characteristics at voltages ≤ 1 V. Despite OMDs potentialities in bioinspired electronics, guidelines for the design of devices and materials are still missing. Here it is shown that the device capacitance represents a significant degree of freedom for targeting devices applications. It is also shown that a single OMD emulates activity dependent synaptic functions and neuronal temporal and spatial summation, taking advantage of its three‐terminals configuration. Interestingly, despite the neuromorphic applications, OMDs can also sense and amplify incoming signals on the basis of their capacitive and/or resistive values. This spectrum of applications, ranging from volatile to non‐volatile characteristics and from neuromorphic computing to bio signals sensing, sets the stage for the realization of integrated circuits for adaptive sensing.
Organic memristive devices are polymeric devices showing neuromorphic and sensing capabilities. Here a range of emulative abilities are presented from the mimicking of synaptic properties to neuronal functions of spatio‐temporal integration. The same device can sense electrocardiogram signals. This combination of neuromorphic properties, memorization capabilities, and sensing abilities suggests their use in integrated circuits with local processing of sensors outputs.
Purpose
This paper aims to present a study on a commercial conductive polylactic acid (PLA) filament and its potential application in a three-dimensional (3D) printed smart cap embedding a resistive ...temperature sensor made of this material. The final aim of this study is to add a fundamental block to the electrical characterization of printed conductive polymers, which are promising to mimic the electrical performance of metals and semiconductors. The studied PLA filament demonstrates not only to be suitable for a simple 3D printed concept but also to show peculiar characteristics that can be exploited to fabricate freeform low-cost temperature sensors.
Design/methodology/approach
The first part is focused on the conductive properties of the PLA filament and its temperature dependency. After obtaining a resistance temperature characteristic of this material, the same was used to fabricate a part of a 3D printed smart cap.
Findings
An approach to the characterization of the 3D printed conductive polymer has been presented. The major results are related to the definition of resistance vs temperature characteristic of the material. This model was then exploited to design a temperature sensor embedded in a 3D printed smart cap.
Practical implications
This study demonstrates that commercial conductive PLA filaments can be suitable materials for 3D printed low-cost temperature sensors or constitutive parts of a 3D printed smart object.
Originality/value
The paper clearly demonstrates that a new generation of 3D printed smart objects can already be obtained using low-cost commercial materials.
In this paper, a three-layer dielectric structure is presented as innovative unit-cell element for transmitarray (TA) antennas with enhanced bandwidth. It consists of a central layer, with a varying ...size square hole, used to compensate the phase of the incident field and located between two other identical layers with linearly tapered square holes, acting as matching circuits. The effectiveness of this unit-cell is demonstrated by the numerical and the experimental results here presented. As a first step, three different TAs with increasing size are designed and simulated: their 1-dB gain bandwidth, centered at 30 GHz, varies from the 30.9% of the smallest configuration, having size of <inline-formula> <tex-math notation="LaTeX">10\lambda _{0}\times 10\lambda _{0} </tex-math></inline-formula>, to the 17.5% of the <inline-formula> <tex-math notation="LaTeX">20\lambda _{0}\times 20\lambda _{0} </tex-math></inline-formula> TA. A slightly modified unit-cell is then designed, with the aim of realizing a prototype with an additive manufacturing (AM) technique. A 3D-printed dielectric TA with a size of <inline-formula> <tex-math notation="LaTeX">15.6\lambda _{0}\times 15.6\lambda _{0} </tex-math></inline-formula> has been manufactured and experimentally characterized. The measured prototype shows excellent performances, achieving a 1-dB gain bandwidth of 21.5%: these results prove the enhanced features of the introduced unit-cell and demonstrate the TA feasibility with AM techniques.
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