Incorporation of Cell-Adhesive Proteins in 3D-Printed Lipoic Acid-Maleic Acid-Poly(Propylene Glycol)-Based Tough Gel Ink for Cell-Supportive Microenvironment

In extrusion-based 3D printing, the use of synthetic polymeric hydrogels can facilitate fabrication of cellularized and implanted scaffolds with sufficient mechanical properties to maintain the structural integrity and physical stress within the in vivo conditions. However, synthetic hydrogels face challenges due to their poor properties of cellular adhesion, bioactivity, and biofunctionality. New compositions of hydrogel inks have been designed to address this limitation. A viscous poly(maleate-propylene oxide)-lipoate-poly(ethylene oxide) (MPLE) hydrogel is recently developed that shows high-resolution printability, drug-controlled release, excellent mechanical properties with adhesiveness, and biocompatibility. In this study, the authors demonstrate that the incorporation of cell-adhesive proteins like gelatin and albumin within the MPLE gel allows printing of biologically functional 3D scaffolds with rapid cell spreading (within 7 days) and high cell proliferation (twofold increase) as compared with MPLE gel only. Addition of proteins (10% w/v) supports the formation of interconnected cell clusters (≈1.6-fold increase in cell areas after 7-day) and spreading of cells in the printed scaffolds without additional growth factors. In in vivo studies, the protein-loaded scaffolds showed excellent biocompatibility and increased angiogenesis without inflammatory response after 4-week implantation in mice, thus demonstrating the promise to contribute to the printable tough hydrogel inks for tissue engineering.     

Ultrasound assisted dispersal of a copper nanopowder for electroless copper activation

This paper describes the ultrasound assisted dispersal of a low wt./vol.% copper nanopowder mixture and determines the optimum conditions for de-agglomeration. A commercially available powder was added to propan-2-ol and dispersed using a magnetic stirrer, a high frequency 850 kHz ultrasonic cell, a standard 40 kHz bath and a 20 kHz ultrasonic probe. The particle size of the powder was characterized using dynamic light scattering (DLS). Z-Average diameters (mean cluster size based on the intensity of scattered light) and intensity, volume and number size distributions were monitored as a function of time and energy input. Low frequency ultrasound was found to be more effective than high frequency ultrasound at de-agglomerating the powder and dispersion with a 20 kHz ultrasonic probe was found to be very effective at breaking apart large agglomerates containing weakly bound clusters of nanoparticles. In general, the breakage of nanoclusters was found to be a factor of ultrasonic intensity, the higher the intensity the greater the de-agglomeration and typically micron sized clusters were reduced to sub 100 nm particles in less than 30 min using optimum conditions. However, there came a point at which the forces generated by ultrasonic cavitation were either insufficient to overcome the cohesive bonds between smaller aggregates or at very high intensities decoupling between the tip and solution occurred. Absorption spectroscopy indicated a copper core structure with a thin oxide shell and the catalytic performance of this dispersion was demonstrated by drop coating onto substrates and subsequent electroless copper metallization. This relatively inexpensive catalytic suspension has the potential to replace precious metal based colloids used in electronics manufacturing.     

Efficient strategy for quality control of screen-printed carbon ink disposable sensor electrodes based on simultaneous evaluation of resistance,capacitance and Faradaic current by Fourier transform AC voltammetry

Two types of mass-produced, screen-printed carbon ink-based macrodisc electrodes suitable for routine sensing applications have been fabricated. Microscopic examination of these carbon ink electrode surfaces reveals that their surfaces are both rough and highly heterogeneous, consisting of random arrays of carbon particles of different sizes, as well as binder. Consequently, they may suffer from a lack of reproducibility in their performance because of variable resistance, capacitance or electroactive area. Use of a Fourier transform AC voltammetric protocol involving application of periodic waveform obtained from summation of five sine waves of variable frequency enabled resistance and capacitance, as well as DC and AC Faradaic currents associated with the model processes or (where FcMeOH is ferrocene methanol) to be assessed from a single experiment. Such data, which may be obtained rapidly via this approach, are highly suitable for quality control assessment.     

Selective Cosmetic Mercury Analysis Using a Silver Ink Screen‐Printed Electrode with Potassium Iodide Solution

A new method for selective determination of trace mercury has been demonstrated by linear scan voltammetry using silver ink screen printed electrode (AgSPE) in presence of potassium iodide (KI) dissolved 0.05 M H₂SO₄ solution. At AgSPE, iodide oxidation peak current signal found to be systematically decreased (inhibitory current anodic peak current signal, i ) with increase in the Hg concentrations, [Hg]. This observation is further utilized for construction of new Hg electroanalytical assays in this work. On the AgSPE, Hg inhibitory detection potential found at 0 V vs. Ag/AgCl, which is 720 mV lower than that of unmodified SPE system. Under optimal experimental conditions, i signals were linearly increased against [Hg] in the window of 500–4500 ppb (40 μM KI) with a correlation coefficient (r) of 0.9988. The limit of detection (LOD) and limit of quantification (LOQ) were 98 and 318 ppb, respectively. This approach was further utilized to analyze hidden Hg in the cosmetic samples. Real sample assays were consistent with that of result obtained from ICP‐OES, which confirm the applicability of the proposed method for practical applications.     

Preparation of stable aqueous conductive ink with silver nanoflakes and its application on paper‐based flexible electronics

A new kind of stable aqueous conductive ink with silver nanoflakes was developed, which was also used to fabricate conductive patterns on weighing paper for flexible electronics by direct writing. Silver nanoflakes of different sizes were characterized by transmission electron microscopy. The physical properties of the conductive ink were investigated by a dynamic contact angle system, Ubbelohde viscometer, and a surface tension instrument. Conductive properties of paper‐based conductive patterns were also investigated by 4‐point probe, scanning electron microscopy, X‐ray diffraction and Uscan explorer with a 3D profilometer system. It is demonstrated how the formulation of conductive ink affects the surface morphology, microstructure conductivity, and line width of conductive patterns. It can be obtained that the paper‐based conductive patterns have low resistivity. Especially, when the sintering condition is 200 °C for 20 min, the resistivity can be down to 9.4 μΩ?cm. The application of the ink on an antenna for radio frequency identification was also studied. Copyright © 2011 John Wiley & Sons, Ltd.     

Real-life applications of the MULVADO software package for processing DOSY NMR data

MULVADO is a newly developed software package for DOSY NMR data processing, based on multivariate curve resolution (MCR), one of the principal multivariate methods for processing DOSY data. This paper will evaluate this software package by using real-life data of materials used in the printing industry: two data sets from the same ink sample but of different quality. Also a sample of an organic photoconductor and a toner sample are analysed. Compared with the routine DOSY output from monoexponential fitting, one of the single channel algorithms in the commercial Bruker software, MULVADO provides several advantages. The key advantage of MCR is that it overcomes the fluctuation problem (non-consistent diffusion coefficient of the same component). The combination of non-linear regression (NLR) and MCR can yield more accurate resolution of a complex mixture. In addition, the data pre-processing techniques in MULVADO minimise the negative effects of experimental artefacts on the results of the data. In this paper, the challenges for analysing polymer samples and other more complex samples will also be discussed.     

Ink‐Jet Printing of Metallic Nanoparticles and Microemulsions

Summary: Two types of ink‐jet inks are presented: ink containing an aqueous dispersion of silver nanoparticles and an oil‐in‐water microemulsion‐based ink. The metallic ink contains nanoparticles of silver, which are formed in the presence of an ionic polymeric stabilizer. Sintering of the printed image obtained with the use of such silver‐based inks at temperatures as low as 300 °C results in formation of patterns possessing noticeable conductivity. The microemulsion inks are based on a thermodynamically stable microemulsion, in which the dispersed oil phase is a volatile solvent containing a water‐insoluble colorant. After contact of the jetted ink droplets with a substrate, nanodroplets of the microemulsion are converted into nanoparticles of the solubilized colorant. In some cases, it was found that the evaporation of microemulsion ink droplets leads to formation of rings composed of ordered nanoparticles.

Scheme of ink‐jet printing of an oil‐in‐water microemulsion followed by conversion of the nanodroplets into nanoparticles, caused by quick evaporation of the solvent within the microemulsion droplets. Therefore, the ink behaves as a dye‐based ink prior to printing, but after printing it behaves like a pigment‐based ink.     

A multifunctional Schiff base with aggregation-induced enhanced emission,gelation, and mechanochromic properties for anti-counterfeiting applications

This work presents a systematic study of three closely related Schiff bases NpSB, AnSB, and PySB for their potential aggregation-induced enhanced emission, gelation, and mechanochromic properties. While aggregation-induced enhanced emission was observed in case of AnSB and PySB due to the suppression of photoinduced electron transfer; PySB also formed a stable gel in DMF?water. Out of three Schiff bases, PySB exhibited reversible mechanochromism. Importantly, on applying pressure or a mechanical force, PySB changed its color from yellow to bright orange under the visible light while its emission wavelength shifted from 580 to 602 nm. More importantly, mechanical-force-induced changes were reversible after fuming with the vapors of CH₂Cl₂ or by heating at 100 °C. The mechanochromism of PySB was studied by a combination of powder X-ray diffraction, scanning electron microscope, differential scanning calorimetry, density functional theory, and nuclear magnetic resonance spectral studies. These studies concluded that the change in color and emission profile was due to change in the molecular packing of PySB after applying the pressure or mechanical force. The slippage of pyrene rings and the conversion of intramolecular H-bonding to intermolecular H-bonding resulted in the alteration of solid-state packing of PySB which was responsible for the mechanochromism. A noteworthy feature of the reversible mechanochromism of PySB was the reversible morphological changes as substantiated by the scanning electron microscope and powder X-ray diffraction studies. PySB was shown to illustrate noteworthy anti-counterfeiting and pressure-induced applications.     

Access to 2,4-Disubstituted Pyrrole-Based Polymer with Long-Wavelength and Stimuli-Responsive Properties via Copper-Catalyzed [3+2] Polycycloaddition

Pyrrole-based polymers ( PBPs ), a type of fascinating functional polymers, play a crucial role in materials science. However, efficient synthetic strategies of PBPs with diverse structures are mainly focused on conjugated polypyrroles and still remain challenging. Herein, an atom and step economy protocol is described to access various 2,4-disubstituted PBPs by in situ formation of pyrrole core structure via copper-catalyzed [3+2] polycycloaddition of dialkynones and diisocyanoacetates. A series of PBPs is prepared with high molecular weight (M_w up to 18 200 Da) and moderate to good yield (up to 87%), which possesses a fluorescent emission located in the green to yellow light region. Blending the PBPs with polyvinyl alcohol, the stretchable composite films exhibit a significant strengthening of the mechanical properties (tensile stress up to 59 MPa, elongation at break >400%) and an unprecedented stress-responsive luminescence enhancement that over fourfold fluorescent emission intensity is maintained upon stretching up to 100%. On the basis of computational studies, the unique photophysical and mechanical properties are attributed to the substitution of carbonyl chromophores on the pyrrole unit.