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Thio-benzothioxanthene imide (BTXI) exhibits long excited state lifetime (τT = 17.7 μs) and high ISC efficiency (ΦΔ = 97%). For the first time, BTXI derivatives were used as photosensitizers for triplet–triplet annihilation upconversion, achieving the highest efficiency of 13.8%. In addition, thio-BTXI derivatives were used as photoinitiators for photopolymerization, resulting in a series of green light-activated radical polymerization systems. [ABSTRACT FROM AUTHOR]

Diblock copolymers of phenyl methacrylate (PMA) and butyl methacrylate (BMA) were synthesized using dual-wavelength photopolymerization with a bifunctional photoinitiator 2-(4-(2-hydroxy-2-methylpropanoyl)phenoxy)ethyl(E)-3-(1-methyl-1H-pyrrol-2-yl)acrylate (PAA-2959). [ABSTRACT FROM AUTHOR]

Twelve liquid crystalline polymer network films were fabricated through photopolymerization of cholesteric liquid-crystalline mixtures containing two aggregation-induced emissive-active luminogens. The films exhibit multicolour and white circularly polarized luminescence with dissymmetry factors up to 0.85 and fluorescence quantum yields up to 90%. [ABSTRACT FROM AUTHOR]

Supramolecular assemblies with chirality inversion were developed using a co-assembly system comprising solvent monomers and a pyridine-cholesterol gelator. The polarity-dependent chiralities were captured in situ through photopolymerization, enabling the formation of multi-color circularly polarized luminescence films. [ABSTRACT FROM AUTHOR]

An approach of 'polymerization of monomers in its aggregated form' is unprecedentedly introduced to (i) tailor the water wettability of fibrous and porous substrates from hydrophobicity to superhydrophobicity, and (ii) associate patterned wettability. A solution of selected monomers—i.e., alkyl acrylate in a good solvent (indicating high solubility; ethanol) was transferred into a bad solvent (refers to poor solubility; water) to achieve a stable dispersion of monomer aggregates of size <1 μm for deposition on fibrous and porous substrates. Its photopolymerization provided a durable coating with the ability to tailor the water wettability from 134° to 153°. Furthermore, a spatially selective photopolymerization process yielded a patterned interface of superhydrophilicity and superhydrophobicity. Such a facile chemical approach with the ability to provide a durable coating embedded with tailored and patterned wettability would be useful for various potential applications. [ABSTRACT FROM AUTHOR]

Two common bio-sourced naphthoquinone derivatives, vitamin K1 (phylloquinone) and vitamin K3 (menadione), were employed in free radical photopolymerization under LED light exposure at 405 nm. In comparison with juglone, a previously reported natural naphthoquinone derivative, both vitamins exhibited enhanced properties in inducing free radical photopolymerization as sole initiators (monocomponent type II) and in combination with amines, and they can act as typical type II photoinitiators. In a three-component photoinitiating system consisting of an iodonium salt, amine and the vitamin, the polymerization process of TMPTA was significantly accelerated/improved too. These three-component systems resulted in faster reactions than the system that solely contains the iodonium salt or amine as the coinitiator, and they can additionally act as sensitizing dyes. Notably, the more polar vitamin K3 alone can initiate PEGDA polymerization with a high conversion rate, suggesting its potential utility in the development of biopolymer materials. The analysis of steady-state photolysis experiments revealed that K3 rapidly reacted with the electron-rich amine under light but was also more likely to generate by-products. In contrast, the inclusion of the iodonium salt in the three-component system significantly accelerated the photolysis of K3, demonstrating the superior chemical reactivity of the three-component system. Electron spin resonance spin trapping experiments successfully captured the radicals that initiated the photopolymerization reaction. Hence, these results facilitated the further deduction of potential reaction pathways. Finally, K1/iodonium salt and K3/amine, two systems that demonstrated strong performance in free radical polymerization experiments, were successfully applied to direct laser write experiments. [ABSTRACT FROM AUTHOR]

Cholesteric liquid crystal polymer networks (CLCNs) with hyper-reflectance have been widely studied for laser protection and energy-saving. Herein, double-layered CLCN films were prepared using single-layered CLCN films with opposite handedness. Since photopolymerization can be carried out in air, the double-layered CLCN films are feasible for being prepared with a large area. Due to the diffusion of the low-molecular-weight compounds of the top layer during the double-layered CLCN film preparation process, the Bragg reflection band of the bottom layer shifts to a long wavelength. Based on this fact, colourful patterns were prepared by printing and screen-printing. These patterns are suitably applied for decoration and anti-counterfeiting. [ABSTRACT FROM AUTHOR]

The use of sunlight to initiate free radical polymerization under air is a key challenge. Due to the associated low light intensity, usual or commercial photoinitiators are characterized by a low efficiency. In this work, seventeen carbazole-fused coumarin-based oxime esters were developed as monocomponent and photocleavable (Type I) initiators of polymerization displaying excellent light absorption properties in the visible range. Compared to the benchmark photoinitiator (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide), some of them (namely OXE-1 and OXE-5) could show photoinitiation performance similar to or better than the reference compound upon irradiation with a LED at 405 nm. The photoinitiation mechanism of these photoinitiators is proposed, supported by theoretical calculations; the detection of CO2 during photopolymerization was performed by means of Fourier transform infrared spectroscopy and the detection of radical species was performed by electron spin resonance analysis. Through direct laser writing, different objects exhibiting an excellent spatial resolution could be obtained. Parallel to the photoinitiating ability, the different photoinitiators also showed a thermal initiation behavior, meaning that these structures can serve both as thermal and photo-initiators on demand. Due to the high sensitivity of these structures to sunlight, OXE-1 and OXE-5 were also investigated as solar photoinitiators (reactive also in Central Europe during winter) and excellent monomer conversions could be obtained within one hour using a multifunctional acrylate monomer (Ebecryl 605). To the best of our knowledge, these two oxime esters constitute the first examples of sunlight activable oxime esters ever reported in the literature. [ABSTRACT FROM AUTHOR]

This document is a back cover of an article titled "Progress on critical cell fabrication parameters and designs for advanced lithium-sulfur batteries" published in Chemical Communications. The article showcases research from Professor Zhou's laboratory at Chongqing University of Posts and Telecommunications in China. It discusses the precision synthesis of diblock copolymers using dual-wavelength photopolymerization with a bifunctional photoinitiator. The article also mentions another related research paper by Jingfang Li et al. The document includes information about EES Batteries, a registered charity, and provides a link for publishing with them. [Extracted from the article]

Advances in the instrumentation and materials for photopolymerization 3D printing aided the use of this powerful technique in the fabrication of microfluidic devices. The costs of printers and supplies have been reduced to the point where this technique becomes attractive for prototyping microfluidic systems with good resolution. With all the development of multi-material 3D printers, most of the microfluidic devices prepared by photopolymerization 3D printing are based on a single substrate material. We developed a digital light processing multi-material 3D printer where two or more resins can be used to prepare complex objects and functional microfluidic devices. The printer is based on a vat inclination system and embedded peristaltic pumps that allow the injection and removal of resins and cleaning step between material changes. Although we have built the whole system, the modification can be incorporated into commercially available printers. Using a high-resolution projector, microfluidic channels as narrow as 43 μm were obtained. We demonstrate the printing of multi-material objects containing flexible, rigid, water-soluble, fluorescent, phosphorescent, and conductive (containing PEDOT or copper nanoparticles) resins. An example of a microfluidic chip containing electrodes for electrochemical detection is also presented. [ABSTRACT FROM AUTHOR]

Organs-on-a-chip, or OoCs, are microfluidic tissue culture devices with micro-scaled architectures that repeatedly achieve biomimicry of biological phenomena. They are well positioned to become the primary pre-clinical testing modality as they possess high translational value. Current methods of fabrication have facilitated the development of many custom OoCs that have generated promising results. However, the reliance on microfabrication and soft lithographic fabrication techniques has limited their prototyping turnover rate and scalability. Additive manufacturing, known commonly as 3D printing, shows promise to expedite this prototyping process, while also making fabrication easier and more reproducible. We briefly introduce common 3D printing modalities before identifying two sub-types of vat photopolymerization – stereolithography (SLA) and digital light processing (DLP) – as the most advantageous fabrication methods for the future of OoC development. We then outline the motivations for shifting to 3D printing, the requirements for 3D printed OoCs to be competitive with the current state of the art, and several considerations for achieving successful 3D printed OoC devices touching on design and fabrication techniques, including a survey of commercial and custom 3D printers and resins. In all, we aim to form a guide for the end-user to facilitate the in-house generation of 3D printed OoCs, along with the future translation of these important devices. [ABSTRACT FROM AUTHOR]

We prepared a series of amino-substituted 9,10-anthraquinone (AQ) derivatives to study the photophysical properties, especially the intersystem crossing (ISC) efficiency and the triplet excited states. Monoamino-substituted AQ derivatives show red-shifted absorption bands centered at 509 nm, as compared to the chloro-AQ derivatives (λabs = 340 nm). Interestingly, attaching an extra amino substituents on the AQ chromophore, i.e. the diamino substituted AQ derivatives, does not induce further red-shifting of the absorption band. We found that only diamino AQ derivatives show decent ISC efficiency (singlet oxygen quantum yield,ΦΔ, is up to 33.3%), whereas the monoamino-AQ derivatives show negligible ΦΔ values. Nanosecond transient absorption spectra indicate the formation of a triplet excited state, and the triplet excited state lifetime was determined to be ca. 2.5 μs. This relatively short triplet excited state lifetime is attributed to the n–π* character of the T1 states of the diamino substituted AQ derivatives, which is supported by DFT computations. We show that the bisamino-substituted AQs can be used as efficient photoinitiators for photopolymerization of alkene monomers, whereas the AQ derivatives with poor ISC capability only show a negligible photopolymerization effect. The mechanism is supposed to be hydrogen abstraction by the photoinitiators at triplet excited states. These results indicate that compounds showing efficient ISC and T1 state with n–π* character can be developed as efficient photoinitiators for radical polymerization of alkene monomers. [ABSTRACT FROM AUTHOR]

Visible light induced polymerizations are a strongly emerging field in recent years. Besides the often mild reaction conditions, visible light offers advantages of spatial and temporal control over chain growth, which makes visible light ideal for functionalization of surfaces and more specifically of nanoscale pores. Current challenges in nanopore functionalization include, in particular, local and highly controlled polymer functionalizations. Using spatially limited light sources such as lasers or near field modes for light-induced polymer functionalization is envisioned to allow local functionalization of nanopores and thereby improve nanoporous material performance. These light sources are usually providing visible light while classical photopolymerizations are mostly based on UV-irradiation. In this review, we highlight developments in visible light induced polymerizations and especially in visible light induced controlled polymerizations as well as their potential for nanopore functionalization. Existing examples of visible light induced polymerizations in nanopores are emphasized. [ABSTRACT FROM AUTHOR]

Chiral polymers always have the edge over their achiral analogues owing to the effective utilization of asymmetry to mimic nature in multiple ways. Chirality in tandem with conjugation in polymers creates an excellent platform for optoelectronic properties, leading to futuristic applications based on chiral photonics. Herein, we design two symmetric bis-functionalised phenylalanine tethered chiral diacetylene (DA) monomers that exhibit efficient topochemical polymerization into conjugated ene–yne polydiacetylene (PDA) with an intense red colour. The efficacy of the photopolymerization can be modulated by altering the peripheral functional groups. Interestingly, the individual enantiomers and their mixture show comparable photopolymerization owing to co-assembly. However, the chiroptical properties of the mixtures can be tweaked by the enantiomeric excess complying with the majority rule principle. Finally, the individual chiral PDA exhibits visible changes in optoelectronic and chiroptical properties under external perturbation e.g. temperature, volatile organic solvent and pH, that are investigated using UV-visible and circular dichroism spectroscopy. Such topochemical polymerization assisted by ordered self-assembly in peptide-tethered diacetylene provides convenient access to smart, responsive, chiral optoelectronic materials. [ABSTRACT FROM AUTHOR]

The UV intensity during photopolymerization allows control over the structural color of a cholesteric liquid crystal (CLC) polymer photonic coating in a single step. Simultaneously, the glass transition temperature (Tg) of the polymer can be tuned by the applied UV intensity. Most likely the low intensity photopolymerization increases the inhibition time, leading to in situ formation of polymer fragments through oxygen inhibition. The formation of polymer fragments changes the matrix during the inhibition time, which results in a color change before the polymer network is formed. Additionally, these fragments inside the network act as a plasticizer, effectively lowering the Tg. This method can be combined with temperature responsive properties based on shape memory to fabricate photonic coatings with multiple, responsive colored patterns. The presented work allows for new functionalities in responsive photonic polymers as multiple colors and response temperatures can be incorporated in a single polymerization step. [ABSTRACT FROM AUTHOR]

A bifunctional diethylene glycol difuran acrylate (DEFA) and a trifunctional trimethylolpropane trifuran acrylate (TMFA) monomer for solid-state photopolymerization were synthesized from a biomass material, furfural. High molar extinction coefficients in the order of 104 indicate the good UV absorption properties of both monomers. The photopolymerization kinetics studies show that DEFA achieves a maximum polymerization rate (Rp) in 54 s and TMFA in 35 s without photoinitiators, and the maximum double bond conversion (DBC) reached 88% for DEFA and 78% for TMFA, which proves that they have high photosensitivity. The addition of the 2,4-dinitroaniline sensitizer increases the maximum DBC, but increases the maximum Rp markedly. The high crystallinity of DEFA and TMFA is prone to photodimerization and forms an amorphous polymer. Both the linear polyester from DEFA and the crosslinked polyester from TMFA have good thermal oxidation stability. Therefore, we developed a strategy to produce highly sensitive monomers for the application of photosensitive materials that polymerize quickly without photoinitiators and solvents. [ABSTRACT FROM AUTHOR]

The microfluidic production of Janus/Hecate polymer microfibers with well-defined interfaces from miscible phases is reported. The process offers tunability of the width and composition of each part of the fibers by controlling the flow rate and nature of the monomers in a single step. The enhanced performances of the fibers are outlined for the simultaneous removal of dyes of opposite charges using amphoteric Janus fibers. [ABSTRACT FROM AUTHOR]

Transformation of supramolecular chiral assemblies into covalent polymers integrates characteristics of supramolecular chemistry together with covalent entities, leading to fabrication of covalent chiral materials through versatile supramolecular chiral assemblies. Here, we report supramolecular assembly of an amphiphilic dendronized 10,12-pentacosadiynoic amide (PCDA) in aqueous solutions to form twisted ribbons, which were transferred into covalent dendronized polydiacetylenes (PDAs) via photopolymerization. These supramolecular dendronized PCDA and the corresponding covalent dendronized PDAs showed unprecedent thermoresponsive properties. The thermally-induced dehydration and aggregations tuned reversibly their chiralities, which can be visually inspected through colour changes. [ABSTRACT FROM AUTHOR]

Fast and well-controlled photoinduced atom transfer radical polymerization (photoATRP) in the organized medium of a bilayer activated by visible light under environmentally friendly mild aqueous conditions leads to polymers with predetermined molecular weight and low dispersity. The decisive parameter for photoATRP of monomers in the organized medium was their mobility and orientation with respect to the bilayer and the photoredox catalyst localized in the interstitial layer. [ABSTRACT FROM AUTHOR]

Acylgermanes are known as highly efficient photoinitiators. In this contribution, we present the synthesis of new diacylgermanes 4a–evia a multiple silyl abstraction methodology. The method outperforms the state-of-the-art approach (Corey–Seebach reaction) towards diacylgermanes in terms of group tolerance and toxicity of reagents. Moreover, these compounds are decorated with bulky mesityl groups in order to improve their storage stability. The isolated diacylgermanes were characterized by multinuclear NMR-, UV-Vis spectroscopy and X-ray crystallography, as well as photolysis experiments (photobleaching) and photo-DSC measurements (photopolymerization behavior). Upon irradiation with an LED emitting at 385 nm, all compounds except for 4a and 4c bleach efficiently with quantum yields above 0.6. Due to their broad absorption bands, the compounds can be also bleached with blue light (470 nm), where especially 4e bleaches more efficiently than Ivocerin®. [ABSTRACT FROM AUTHOR]

Azacalixphyrins are unique aromatic macrocycles featuring strong absorption from the visible to the near-infrared (NIR) spectral ranges. This work demonstrates through EPR spin-trapping experiments that the N-alkyl tetrasubstituted azacalixphyrin (ACP) can lead to the formation of carbon-centered radicals initiating for the free-radical photopolymerization (FRP) of bio-based acrylate monomer upon the irradiation of several light emitting diodes, which emissions range from 455 to 660 nm. Compared to other previously reported systems, the tremendous advantage of the ACP photoinitiating system is its ability to promote photopolymerization on its own, avoiding the introduction of co-initiators. A new potential application of this promising photoinitiator is highlighted through the fabrication of well-defined microstructures under NIR laser diode irradiation at λ = 800 nm. [ABSTRACT FROM AUTHOR]

Radical initiation upon LED light irradiation is discussed herein as well as its application in additive manufacturing. The ability of manufacturing complex structures, freedom of design, low energy consumption, fast prototyping, and excellent spatial resolution are the main benefits of the 3D printing technology by photopolymerization. Therefore, the 3D printing of composites through photopolymerization processes is developing rapidly in the academia and industry, and has been a turning point of additive manufacturing (AM). In the present review, an overview of radical initiation with LEDs (i.e., the photopolymerization LED technology, the photoinitiating systems, and the polymerizable media) and of the main 3D printing methods by photopolymerization, materials, and their applications in different fields has been carried out. As a challenging topic, the issue of light penetration in a filled matrix for the access to composites is discussed, including the light transmittance of the composite, the mismatch of the refractive index between the filler and the monomer, the factors of the filler, and the adverse influence of low light penetration on the 3D printing process. In particular, the popular applications of 3D printing by photopolymerization in biomedical science, electronic industry, materials for adsorption, and 4D printing are discussed. Overall, this review gives an overview of the 3D printing of polymer matrix composites through photopolymerization processes as a benchmark for future research and development. [ABSTRACT FROM AUTHOR]

A 2D coordination polymer, 1, was synthesized, characterized, and investigated with single-crystal-to-single-crystal photoreaction and thermal pyrolysis. It could undergo two-step photoaddition upon UV irradiation: at the first step, the parallel polycatenated 2D topology of the structure changed into 4-fold interpenetrating 3D nets; at the second step, a new compound with an unreported 3D net topology was formed. Upon heating, the cyclobutanes in the photoreaction product underwent a ring opening reaction. The photoluminescence of 1 was determined by its structure; it emitted green fluorescence, and after photoaddition and photopolymerization, it emitted blue fluorescence. 1 may be a photo/thermo-switchable dual-color green-to-blue fluorescence material. [ABSTRACT FROM AUTHOR]

We report a rapid fabrication strategy of highly transparent piezoresistive balls with excellent pressure-sensitivity and toughness by photopolymerization of polymerizable deep eutectic solvents. By careful design and integration, a number of optoelectronic devices have been constructed with the piezoresistive balls as building blocks. [ABSTRACT FROM AUTHOR]

Two diene molecules were shown to undergo photopolymerization reactions in their metal–organic gels and xerogels, while their respective crystalline CPs are photostable. These reactions reveal the advantages of the gels and xerogels compared to their crystalline counterparts and also the utility of Ag⋯Ag interactions in the gels to promote topochemical polymerizations. [ABSTRACT FROM AUTHOR]

The photo-induced polymerization to covalently link metal–organic polyhedra (MOPs) by flexible polymer chains is reported for the first time, which endows MOPs with enhanced processability, dispersity, and hydrostability. The resultant hybrid material exhibits 9 times higher capacity and much better reusability than bulk MOPs in the adsorption of methylene blue. [ABSTRACT FROM AUTHOR]

We propose a simple but efficient multiplex coaxial flow focusing (MCFF) process for single-step fabrication of multicompartment Janus microcapsules (MJMs) in a wide range of operating parameters. The produced MJMs consist of a multicompartmental core–shell structure with material compositions tunable in individual shell and core compartments. Potential applications of such a MJM agent are demonstrated in both benchtop and in vitro experiments. For the benchtop experiment, magnetic nanoparticles are loaded into one of the shell compartments and photopolymerized under ultraviolet light for controlled alignment and rotation of the microcapsules in a magnetic field. For the in vitro experiment, four different types of cells are encapsulated in the desired compartments of sodium alginate MJMs and co-cultured for seven days. By increasing the number of coaxial needles, we are also able to produce MJMs with three or more compartments. Our studies have shown that the proposed MCFF process is able to produce MJMs with desired material compositions and narrow size distribution. This process is inexpensive and scalable for mass production of various MJMs in its potential applications in biomedical imaging, drug delivery, and regenerative medicine. [ABSTRACT FROM AUTHOR]

A method was developed for the specific entrapment and separation of phosphorylated compounds using a Phos-tag polyacrylamide gel fabricated at the channel crossing point of a microfluidic electrophoresis chip. The channel intersection of the poly(methyl methacrylate)-made microchip was filled with a solution comprising acrylamide, N,N-methylene-bis-acrylamide, Phos-tag acrylamide, and 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], which functioned as a photocatalytic initiator. In situ polymerization at the channel crossing point was performed by irradiation with a UV LED laser beam. The fabricated Phos-tag gel (100 × 100 × 30 μm) contains ca. 20 fmol of the Phos-tag group and therefore could entrap phosphorylated compounds at the femtomolar level. The electrophoretically trapped phosphorylated compounds were released from the gel by switching the voltage to deliver high concentrations of phosphate and EDTA in a background electrolyte. The broad sample band eluted from the gel was effectively reconcentrated at the boundary of a pH junction generated by sodium ions delivered from the outlet reservoir. The reconcentrated sample components were then separated and fluorometrically detected at the end of the separation channel. Under the optimized conditions, the phosphorylated compounds were concentrated by a factor of 100-fold, and the peak resolution was comparable to that obtained by pinched injection. This method was successfully utilized to preconcentrate and analyze phosphorylated peptides in a complex peptide mixture. [ABSTRACT FROM AUTHOR]

Membrane functionality is crucial in microfluidics for realizing operations such as filtration, separation, concentration, signaling among cells and gradient generation. Currently, common methods often sandwich commercially available membranes in multi-layer devices, or use photopolymerization or temperature-induced gelation to fabricate membrane structures in one-layer devices. Biofabrication offers an alternative to forming membrane structures with biomimetic materials and mechanisms in mild conditions. We have recently developed a biofabrication strategy to form parallel biopolymer membranes in gas-permeable polydimethylsiloxane (PDMS) microfluidic devices, which used positive pressure to dissipate air bubbles through PDMS to initiate membrane formation but required careful pressure balancing between two flows. Here, we report a technical innovation by simply placing as needed an add-on PDMS vacuum layer on PDMS microfluidic devices to dissipate air bubbles and guide the biofabrication of biopolymer membranes. Vacuuming through PDMS was simply achieved by either withdrawing a syringe or releasing a squeezed nasal aspirator. Upon vacuuming, air bubbles dissipated within minutes, membranes were effortlessly formed, and the add-on vacuum layer can be removed. Subsequent membrane growth could be robustly controlled with the flows and pH of solutions. This new process is user-friendly and has achieved a 100% success rate in more than 200 trials in membrane biofabrication. [ABSTRACT FROM AUTHOR]

In this study, molecularly imprinted films with concave and convex hemispherical patterns were fabricated using soft lithography and photopolymerization, and their dynamic sensing properties were compared using the gravimetric detection of caffeine. [ABSTRACT FROM AUTHOR]

A novel long-chain branching (LCB) hydrogel, polyacrylamide grafted from poly(2-acrylamido-2-methylpropanesulfonic acid) via photo-induced polymerization, has been developed with excellent mechanical properties such as ultrahigh tensibility and high strength. Investigations of tensile and compressive properties indicate that the Young's modulus, ultimate strength and strain, toughness, compressive modulus and stress are significantly improved by introduction of LCB. Scanning electron microscopy (SEM) reveals that the amount of embedded micro-network structures in LCB gels is increased with an increase in the length of LCB. The compressive loading–unloading behaviour shows that the area of the hysteresis loop (the dissipated energy) for the first compressive cycle increases with the introduction of LCB and is higher than that for subsequent cycles. The energy dissipation mechanism is demonstrated for a better understanding of LCB gels. Furthermore, rheological measurements are also studied. Dynamic shear measurements show that both the storage modulus and the complex viscosity increase in the presence of LCB. [ABSTRACT FROM AUTHOR]

We report the use of a laser-based direct-write (LDW) technique that allows the design and fabrication of three-dimensional (3D) structures within a paper substrate that enables implementation of multi-step analytical assays via a 3D protocol. The technique is based on laser-induced photo-polymerisation, and through adjustment of the laser writing parameters such as the laser power and scan speed we can control the depths of hydrophobic barriers that are formed within a substrate which, when carefully designed and integrated, produce 3D flow paths. So far, we have successfully used this depth-variable patterning protocol for stacking and sealing of multi-layer substrates, for assembly of backing layers for two-dimensional (2D) lateral flow devices and finally for fabrication of 3D devices. Since the 3D flow paths can also be formed via a single laser-writing process by controlling the patterning parameters, this is a distinct improvement over other methods that require multiple complicated and repetitive assembly procedures. This technique is therefore suitable for cheap, rapid and large-scale fabrication of 3D paper-based microfluidic devices. [ABSTRACT FROM AUTHOR]

A visible-light (470 nm wavelength) sensitive Type II photoinitiator system is developed for bulk Cu(i)-catalyzed azide–alkyne cycloaddition (CuAAC) reactions in crosslinked networks. The accelerated photopolymerization eliminates UV-mediated azide decomposition allowing for the formation of defect-free glassy networks which exhibit a narrow glass transition temperature. [ABSTRACT FROM AUTHOR]

Tough hydrogels are prepared from two monomers via photopolymerization of hydroxyethyl acrylate and sol–gel of methyltrimethoxysilane. Constitution and water content could be tuned easily because of the good water solubility of both monomers and two non-interfering polymerization processes. The hydrogels exhibit excellent integrated performance with toughness, high resilience, fast self-recovery, and self-healing. [ABSTRACT FROM AUTHOR]

Since its conception during the 80s, 3D-printing, also known as additive manufacturing, has been receiving unprecedented levels of attention and interest from industry and research laboratories. This is in addition to end users, who have benefited from the pervasiveness of desktop-size and relatively cheap printing machines available. 3D-printing enables almost infinite possibilities for rapid prototyping. Therefore, it has been considered for applications in numerous research fields, ranging from mechanical engineering, medicine, and materials science to chemistry. Electrochemistry is another branch of science that can certainly benefit from 3D-printing technologies, paving the way for the design and fabrication of cheaper, higher performing, and ubiquitously available electrochemical devices. Here, we aim to provide a general overview of the most commonly available 3D-printing methods along with a review of recent electrochemistry related studies adopting 3D-printing as a possible rapid prototyping fabrication tool. [ABSTRACT FROM AUTHOR]

PEG-based hydrogels have become widely used as drug delivery and tissue scaffolding materials. Common among PEG hydrogel-forming polymers are photopolymerizable acrylates such as polyethylene glycol diacrylate (PEGDA). Microfluidics and microfabrication technologies have recently enabled the miniaturization of PEGDA structures, thus enabling many possible applications for nano- and micro- structured hydrogels. The presence of oxygen, however, dramatically inhibits the photopolymerization of PEGDA, which in turn frustrates hydrogel formation in environments of persistently high oxygen concentration. Using PEGDA that has been emulsified in fluorocarbon oil via microfluidic flow focusing within polydimethylsiloxane (PDMS) devices, we show that polymerization is completely inhibited below critical droplet diameters. By developing an integrated model incorporating reaction kinetics and oxygen diffusion, we demonstrate that the critical droplet diameter is largely determined by the oxygen transport rate, which is dictated by the oxygen saturation concentration of the continuous oil phase. To overcome this fundamental limitation, we present a nitrogen micro-jacketed microfluidic device to reduce oxygen within the droplet, enabling the continuous on-chip photopolymerization of microscale PEGDA particles. [ABSTRACT FROM AUTHOR]

Widely used medical diagnostic devices and assays that sense the presence of a particular molecule in a bodily fluid often rely on either a nanoparticle label or an enzymatic reaction to generate a signal that is easily detectable. In many cases, it is desirable if the magnitude of the signal correlates with the concentration of the molecule of interest. Photo-initiated polymerization reactions are an alternative means of generating amplified signals that can be used to quantify biological molecules in complex fluids. In this case, the formation of a polymer, typically a cross-linked hydrogel, signifies the presence of the molecule of interest. This tutorial review explains how photo-initiated polymerization reactions have been used in a conditional manner to detect and quantify molecular recognition events. We weigh the advantages and disadvantages of using photo-initiated reactions in comparison with other approaches and highlight exciting directions and opportunities in this area. [ABSTRACT FROM AUTHOR]

The photopolymerization of Co(ii)/Co(iii) complexes for dye-sensitized solar cells (DSSCs) by means of a fast, inexpensive, in situ and inhibition-free process has been examined. We have succeeded in fabricating high-performance DSSCs able to retain a light-to-electricity power conversion efficiency exceeding 6.5% (8.5% at low intensity) after 1800 h of mixed (light on/off, temperature high/low) accelerated aging tests, thus revealing a possible way for the stabilization of these record-holding redox pairs. [ABSTRACT FROM AUTHOR]

We report the use of a new laser-based direct-write technique that allows programmable and timed fluid delivery in channels within a paper substrate which enables implementation of multi-step analytical assays. The technique is based on laser-induced photo-polymerisation, and through adjustment of the laser writing parameters such as the laser power and scan speed we can control the depth and/or the porosity of hydrophobic barriers which, when fabricated in the fluid path, produce controllable fluid delay. We have patterned these flow delaying barriers at pre-defined locations in the fluidic channels using either a continuous wave laser at 405 nm, or a pulsed laser operating at 266 nm. Using this delay patterning protocol we generated flow delays spanning from a few minutes to over half an hour. Since the channels and flow delay barriers can be written via a common laser-writing process, this is a distinct improvement over other methods that require specialist operating environments, or custom-designed equipment. This technique can therefore be used for rapid fabrication of paper-based microfluidic devices that can perform single or multistep analytical assays. [ABSTRACT FROM AUTHOR]

A series of polydiacetylene (PDA) – based micelles were prepared from diacetylenic surfactant bearing polyethylene glycol, by increasing UV-irradiation times. These polymeric lipid micelles were analyzed by physicochemical methods, electron microscopy and NMR analysis. Cellular delivery of fluorescent dye suggests that adjusting the polymerization state is vital to reach the full in vitro potential of PDA-based delivery systems. [ABSTRACT FROM AUTHOR]

Thiol–yne photopolymerization in miniemulsion is demonstrated as a simple, rapid, and one-pot synthetic approach to polythioether nanoparticles with tuneable particle size and clickable functionality. The strategy is also useful in the synthesis of composite polymer–inorganic nanoparticles. [ABSTRACT FROM AUTHOR]

Two hyperbranched oligomers with renewable cardanol side groups and multiple photopolymerizable acrylates were designed and synthesized. The structures of the hyperbranched oligomers were characterized by 1H NMR and FTIR spectroscopy. The synthesized oligomers contain rigid carbon rings as “hard cores” and long reactive fatty chains as “flexible shells”. The photopolymerization kinetics, thermodynamic properties and mechanical properties of the UV cured films were studied and compared with a petrochemical based hyperbranched acrylate CN2302. The cardanol-based polymers with “hard core, flexible shell” structures have higher double bond conversion and higher Tg but lower thermal stability. Much improved surface mechanical properties such as nanoindentation hardness, reduced modulus, surface storage modulus and storage stiffness can be obtained for the plant oil-based polymers. These biorenewable, UV curable cardanol-based oligomers show promise in “green + green” materials technologies. [ABSTRACT FROM AUTHOR]

This work reported a high quality photonic crystal film with an ultra-narrow photonic bandgap obtained via a chemical synthetic route. The bandgap is much narrower than that of traditional colloidal crystals, which makes the film qualified for use in optical devices. The narrow PBG originates from not only the high crystallinity and uniform orientations of microcrystals within the film but also the very close refractive indices between the silica and the polymer matrix. Due to the matching of the refractive index, the amorphous contents of the film are optically transparent and do not interfere with the reflection, so that the photonic crystal film is tolerant of the existence of disordered contents. [ABSTRACT FROM AUTHOR]

A photo-polymerization protocol, utilizing a pre-formed and well-characterized Cu(ii) formate complex, [Cu(Me6-Tren)(O2CH)](ClO4), mediated by UV light is described. In the absence of additional reducing agents and/or photosensitizers, ppm concentrations of the oxidatively stable [Cu(Me6-Tren)(O2CH)](ClO4), furnish near-quantitative conversions within 2 h, yielding poly(acrylates) with low dispersities (∼1.10) and exceptional end-group fidelity, capable of undergoing in situ chain extension and block copolymerization. [ABSTRACT FROM AUTHOR]

A linear ABA type diacrylic macromer containing an amphiphilic backbone composed of a siloxane block (SiO) and two polyoxyethylene blocks (EO) was synthesized and subsequently photopolymerized and copolymerized with a polyoxyethylene diacrylate. The kinetics of the photopolymerization was monitored by rt-FTIR, confirming the reactivity of the acrylic functionalities. The obtained polymers were then characterized by DMTA analyses and showed interesting biphasic morphology with two Tgs attributable to the EO domains and to the SiO domains. Swelling in different solvents was also tested: compared to siloxane acrylates, the introduction of EO enhanced the chemical resistance of the polymer to most solvents, excluding water. Surface analyses showed that the incorporation of both hydrophobic siloxane groups and hydrophilic polyoxyethylene groups into the networks is a successful method for controlling their surface; due to the preferential segregation of the SiO blocks at the air interface, the wettability of the polymers with water is very low, but can change depending on the environment. Compatibility toward DNA amplification reaction was successfully tested. As the possibility of fast, accurate, and cheap reproducibility of microdevices by liquid phase photopolymerization increases the attractiveness of the polymer, this material is a good alternative to polydimethylsiloxane for the fabrication of microfluidic chips for biological analysis purposes. [ABSTRACT FROM AUTHOR]

Capillary barriers provide a simple and elegant means for autonomous fluid-flow control in microfluidic systems. In this work, we report on the fabrication of periodic hydrogel microarrays in closed microfluidic systems using non-fluorescent capillary barriers. This design strategy enables the fabrication of picoliter-volume patterns of photopolymerized and thermo-gelling hydrogels without any defects and distortions. [ABSTRACT FROM AUTHOR]

A robust strategy is explored to graft poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brushes on two-dimensional vanadium carbide (V2C) materials through self-initiated photografting and photopolymerization (SIPGP). CO2 and temperature dual-responsive properties of PDMAEMA allow this hybrid to be used as a smart system for tuning the transmittance and conductivity of V2C. [ABSTRACT FROM AUTHOR]

Gels are a functional template for micro-particle fabrication and microbiology experiments. The control and knowledge of their mechanical properties is critical in a number of applications, but no simple in situ method exists to determine these properties. We propose a novel microfluidic based method that directly measures the mechanical properties of the gel upon its fabrication. We measure the deformation of a gel beam under a controlled flow forcing, which gives us a direct access to the Young's modulus of the material itself. We then use this method to determine the mechanical properties of poly(ethylene glycol) diacrylate (PEGDA) under various experimental conditions. The mechanical properties of the gel can be highly tuned, yielding two order of magnitude in the Young's modulus. The method can be easily implemented to allow for an in situ direct measurement and control of Young's moduli under various experimental conditions. [ABSTRACT FROM AUTHOR]

Alkoxyamines - per-alkylated derivatives of hydroxylamine R¹R²NO-R³ - can undergo C-ON bond homolysis to release a persistent nitroxyl radical R¹R²NO* and a transient alkyl radical R³*. Although they were considered as an oddity when discovered in 1974, their properties have been extensively studied since the seminal work of Solomon, Rizzardo and Cacioli (Chem. Abstr., 102, 221335q), who patented the key role of alkoxyamines in nitroxide-mediated polymerization (NMP) in 1985. This feature article surveys and assesses the various applications of alkoxyamines: in tin-free radical chemistry, e.g., for the elaboration of carbo- or hetero-cycles, for the development of new reactions, for total synthesis of natural products; in polymerization under thermal conditions (NMP) or photochemical conditions (nitroxide-mediated photopolymerization, NMP2); and in the design of smart materials. In this feature article, we also describe our recent findings concerning the chemical triggering of the C-ON bond homolysis in alkoxyamines, affording the controlled generation of alkyl radicals at room temperature. Based on these results, we describe herein some new opportunities for applications in the field of smart materials, and of course, some possible developments as new initiators for NMP as well as an entirely new field of application: the use of alkoxyamines as theranostic agents. Indeed, each of the radicals released after homolysis can play an appealing role: the nitroxide, through dynamic nuclear polarization (DNP), can be used for imagery purposes (diagnostic properties), while the alkyl radical can be used to induce cellular disorders in abnormal cells (therapeutic activity). [ABSTRACT FROM AUTHOR]