Influence of etching solvent evaporation on the size of micro-via holes in PVP thin films

Via holes are a necessary component in traditional PCBs and IC interconnections. Such structures will also be required in organic electronics to achieve vertical communication between multiple layers. Inkjet printing has demonstrated its applicability in both hole creation and for other pattern generation requirements in various polymeric layers. However, the technique has not been systematically investigated. This paper is focused on a study of the effect of solvent evaporation rate on the size of inkjet-etched via holes for organic electronics, which is part of a more extensive investigation and evaluation of inkjet etching as a via hole fabrication technique. In this work, holes were etched in thin layers of poly(4-vinyl phenol) (PVP), which is a potential dielectric material for organic electronic structures. Ethanol, isobutanol and ethylene glycol were used as the etchants in order to study the effect of solvent boiling point and vapour pressure on the size evolution of via holes with the total number and the frequency of the solvent drops used to dissolve them. Isobutanol and ethylene glycol have higher boiling points than ethanol, leading to slower evaporation, which is believed to allow the dissolved polymer to flow backwards to the central area before complete solvent evaporation, resulting in hole refill. However it will be shown that applying temperatures higher than room temperature can accelerate solvent evaporation and eliminate the refill issue

Electrical conductive, characteristics of ACA bonding: a review of the literature, current challenges and future prospects.

Anisotropic Conductive Adhesives (ACAs) have been used in fine pitch electronics packaging for over a decade and provide a high density and low temperature bonding method in a range of niche applications. The principal objective of this paper is to provide significant insights into the basic conductive characteristics of ACAs based on a review of previously reported scientific research, and to identify the current challenges and future prospects for this technology. In order to provide a concise, structured overview of this topic, many detailed conductive models, mathematical solutions and research methodologies are presented based on the reviewed literature. These models can partially explain the conductive mechanisms of an ACA particle, but make a number of important sirnplifying assumptions. However, one model was developed and can be used to explain the conductive mechanism of an ACA particle more successfully. In conclusion, existing computational models, mathematical models and physical models have been used to estimate the resistance of an ACA particle and the particle contact area, and therefore constriction resistance, for a given degree of particle deformation, thereby almost achieving a model for the whole resistance of an ACA joint. The paper will close by identifying other research challenges remaining for this important electronics interconnection technology

Fine pitch printing on a non-woven fabric for high frequency applications

Interest in wireless body area networks (WBAN) operating in the millimetre-wave regime (60 GHz) is increasing due to concerns over the security of data transfer. Obtaining fine pitch in this frequency regime is essential, as the design dimensions scale inversely with wavelength. In the area of wearable electronics, printing onto fabrics is challenging, due to the porosity of the material. Some researchers have considered screen printing for realising interconnects onto fabrics. In this paper, inkjet printing is investigated for fine pitch printing on a nonwoven fabric targeted for high frequency applications

A novel yet effective motion artefact reduction method for continuous physiological monitoring

This study presents a non-invasive and wearable optical technique to continuously monitor vital human signs as required for personal healthcare in today’s increasing ageing population. The study has researched an effective way to capture human critical physiological parameters, i.e., oxygen saturation (SaO2%), heart rate, respiration rate, body temperature, heart rate variability by a closely coupled wearable opto-electronic patch sensor (OEPS) together with real-time and secure wireless communication functionalities. The work presents the first step of this research; an automatic noise cancellation method using a 3-axes MEMS accelerometer to recover signals corrupted by body movement which is one of the biggest sources of motion artefacts. The effects of these motion artefacts have been reduced by an enhanced electronic design and development of self-cancellation of noise and stability of the sensor. The signals from the acceleration and the opto-electronic sensor are highly correlated thus leading to the desired pulse waveform with rich bioinformatics signals to be retrieved with reduced motion artefacts. The preliminary results from the bench tests and the laboratory setup demonstrate that the goal of the high performance wearable opto-electronics is viable and feasible

Effect of microstructure on anomalous strain-rate-dependent behaviour of bacterial cellulose hydrogel

This study is focused on anomalous strain-rate-dependent behaviour of bacterial cellulose (BC) hydrogel that can be strain-rate insensitive, hardening, softening, or strain-rate insensitive in various ranges of strain rate. BC hydrogel consists of randomly distributed nanofibres and a large content of free water; thanks to its ideal biocompatibility, it is suitable for biomedical applications. Motivated by its potential applications in complex loading conditions of body environment, its time-dependent behaviour was studied by means of in-aqua uniaxial tension tests at constant temperature of 37 °C at various strain rates ranging from 0.0001 s- 1 to 0.3 s- 1. Experimental results reflect anomalous strain-rate-dependent behaviour that was not documented before. Micro-morphological observations allowed identification of deformation mechanisms at low and high strain rates in relation to microstructural changes. Unlike strain-rate softening behaviours in other materials, reorientation of nanofibres and kinematics of free-water flow dominate the softening behaviour of BC hydrogel at high strain rates

Surface Treatments for Inkjet Printing onto a PTFE-Based Substrate for High Frequency Applications

In this paper, different surface treatments to reduce the surface roughness of a typical laminate for use in high frequency applications (high frequency laminate) are investigated. In particular, the importance of matching the substrate surface energy to the ink to achieve a smooth coated layer for the case of a UV cured insulator is demonstrated. This paper shows that this is achievable within the parameters of heating the platen, which is a more flexible approach compared to modifying the ink to improve the ink-substrate interaction. In printing onto the surface modified substrates, the substrate roughness was observed to affect the printed line width significantly. A surface roughness factor was introduced to take into account the phenomenon by modifying the original formula of Smith et al. (<i>J. Mater. Sci</i>. <b>2006</b>, <i>41</i>, 4153). Lastly, the authors show that the printed line widths are also influenced by the surface tension arising from charges present on the surface modified substrates

MOESM1 of Enhancement of the catalytic activity of Isopentenyl diphosphate isomerase (IDI) from Saccharomyces cerevisiae through random and site-directed mutagenesis

Additional file 1. Methods, Tables and Figures

Dehydration of bacterial cellulose and the water content effects on its viscoelastic and electrochemical properties

<p>Bacterial cellulose (BC) has interesting properties including high crystallinity, tensile strength, degree of polymerisation, water holding capacity (98%) and an overall attractive 3D nanofibrillar structure. The mechanical and electrochemical properties can be tailored upon incomplete BC dehydration. Under different water contents (100, 80 and 50%), the rheology and electrochemistry of BC were evaluated, showing a progressive stiffening and increasing resistance with lower capacitance after partial dehydration. BC water loss was mathematically modelled for predicting its water content and for understanding the structural changes of post-dried BC. The dehydration of the samples was determined via water evaporation at 37 °C for different diameters and thicknesses. The gradual water evaporation observed was well-described by the model proposed (<i>R</i> ² up to 0.99). The mathematical model for BC water loss may allow the optimisation of these properties for an intended application and may be extendable for other conditions and purposes.</p

Construction of Substituted Benzenes via Pd-Catalyzed Cross-Coupling/Cyclization Reaction of Vinyl Halides and Terminal Alkynes

A tandem Sonogashira coupling/cyclization/aromatization sequence of β-halo vinyl sulfones/ketones with terminal alkynes has been developed for the construction of benzene rings. Polysubstituted functionalized benzenes containing a sulfonyl or an acyl group could be obtained in up to 95% yield

Enzyme Stabilization and Catalytic Activity Enhancement by Single-Chain Nanoparticles of Fluorinated Zwitterionic Random Copolymers

To achieve convenient storage of bioactive materials such as protein enzymes (proteases) at ambient temperature, with both their spatial structure and biocatalytic activity well retained, is highly appealing but challenging. Herein, a variety of amphiphilic random copolymers have been well synthesized via reversible addition–fragmentation chain transfer (RAFT) copolymerization of sulfobetaine methacrylate (SBMA) and various length fluoroalkyl methacrylate monomers. By simultaneously introducing fluoroalkyl and zwitterionic segments in random copolymerization, such kinds of amphiphilic random copolymers combined the advantages of both polyzwitterionic and fluoropolymers, which were capable of constructing uniform tiny single-chain nanoparticles (SCNPs) of around 10 nm in a wide range of compositions and fabrication conditions from aqueous solutions. Through intramolecular self-folding of the fluorinated alkyl segments to constitute the compact inner cores and the superhydrophilic zwitterionic SBMA polymer segments forming the outer passivated layer, the thus obtained SCNPs exhibited remarkable enzyme stabilizing capability through morphological adjustment, hydration, and heterocoagulation mechanisms for the investigated glucose oxidase (GOx) and horse radish peroxidase (HRP), acting like artificial molecular chaperones. Moreover, enzyme catalytic activity enhancement in the HRP@SCNPs system was well demonstrated with a representative enzyme-catalyzed cascade oxidization reaction for the synthesis of an azobenzene chromophore. Therefore, this work provides a facile fabricating strategy for SCNPs from well-synthesized amphiphilic random copolymers via RAFT, which may serve as promising stabilizers for ambient temperature storage and activity preservation of proteases