Metal–organic frameworks (MOFs) are a well-developed field of materials, having a high potential for various applications such as gas storage, water purification, and catalysis. Despite the continuous discoveries of new MOFs, so far there are only a limited number of industrial applications, partially due to their low chemical stability and limited mechanical properties, as well as difficulties in integration within functional devices, Herein, a new approach is presented toward the fabrication of MOF-based devices, utilizing direct 3D printing. By this method, 3D, flexible, and hydrolytically stable MOF-embedded polymeric structures are fabricated. It is found that the adsorption capacity of the 3D-printed MOF is retained, with significantly improved hydrolytic stability of the printed MOFs (copper benzene-1,3,5-tricarboxylate) compared to the MOF only. It is expected that applying 3D printing technologies, for the fabrication of functional MOF objects such as filters and matrices for columns and flow reactors, will open the way for utilization of this important class of materials.

Vanadium dioxide (VO2) nanoparticles with reversible semiconductor-metal phase transition holds the tremendous potential as a thermochromic material for the energy-saving smart glazing. However, the trade-off between improving the luminous transmittance (Tlum) while sacrificing the solar modulation ability (ΔTsol) hampers its bench-to-market translation. Previous studies of anti-reflection coatings (ARCs) focused primarily on increasing Tlum while neglecting ΔTsol, which is a key energy-saving determinant. The intrinsically low ΔTsol (<16%) is due to the fact that VO2 has a higher refractive index (RI) from 500 nm to 2200 nm wavelength (λ) below its critical transition temperature (τc), which causes excessive reflection at a lower temperature. This study aims to investigate ARCs with tunable RI (1.47–1.92 at λ = 550 nm) to improve the antireflection effect at a lower temperature, thereby maximizing ΔTsol for various VO2 nanosubstrates, e.g. continuous thin films, nanocomposites, and periodic micro-patterning films. We showed that the best performing coatings could maximize ΔTsol (from 15.7% to 18.9%) and increase Tlum(avg) (from 39% to 44%) simultaneously, which surpasses the current bench-mark specifications ever reported for ARC-coated VO2 smart glazing. In addition, the cytotoxicity analyses evidence that ARCs are feasible to improve the cyto-compatibility of VO2 nanoparticles-based nanocomposites. The presented RI-tunable ARC, which circumvents the complex materials selection and optical design, not only paves the way for practical applications of VO2-based smart windows but also has extensive applications in the field of solar cells, optical lenses, smart display, etc.

The trend of developing electrochemical sensors toward cellular level detection put forward higher requirements of the electrodes in the detection performance. However, common disk electrodes or conventional screen printing electrodes meet up with some limitations in the electrocatalytic activity and electron transfer capability. In this work, we applied inkjet printing technology to fabricate electrodes to make some improvements. Highly conductive Ag nanoparticles based electrodes were obtained on plastic substrate by inkjet printing technology followed by a sintering process at room temperature. The resistivity of IPAgE is determined to be 64.0 $\pm$ 5.3 μΩ cm. With better conductivity and the nanoparticle-based interface, superb electrochemical response of IPAgE for H2O2 was obtained, nearly 300-fold higher than the conventional screen printed Ag electrode. Moreover, high sensitivity of 287 μA mM−1 cm−2 with a LOD of 5.0 μM was obtained under the optimized 20 printed layers. The inkjet printed Ag electrodes were also credibly applied in the detection of H2O2 release from living cells. This work demonstrates inkjet printing is a promising method for the high performance electrochemical sensors.

The field of printed electronics is continually trying to reduce the dimensions of the elec. components. Here, a method of printing metallic lines with widths as small as 15 nm and up to a few micrometers using fountain pen nanolithog. (FPN) is shown. The FPN technique is based on a bent nanopipette with at. force feedback that acts similar to a nanopen. The geometry of the nanopen allows for rapid placement accuracy of the printing tip, on any desired location, with the highest of optical sub-micrometer resoln. Using this nanopen, investigations of various inks are undertaken together with instrumental and script-tool development that allows accurate printing of multiple layers. This has led to the printing of conductive lines using inks composed of silver nanoparticles and salt solns. of silver and copper. In addn., it is shown that the method can be applied to substrates of various materials with minimal effect on the dimension of the line. The line widths are varied by using nanopens with different orifices or by tailoring the wetting properties of the ink on the substrate. Metallic interconnections of conducting lines are reported. [on SciFinder(R)]

Bioelectronics platforms are gaining widespread attention as they provide a template to study the interactions between biological species and electronics. Decoding the effect of the electrical signals on the cells and tissues holds the promise for treating the malignant tissue growth, regenerating organs and engineering new-age medical devices. This work is a step forward in this direction, where bio- and electronic materials co-exist on one platform without any need for post processing. We fabricate a freestanding and flexible hydrogel based platform using 3D bioprinting. The fabrication process is simple, easy and provides a flexible route to print materials with preferred shapes, size and spatial orientation. Through the design of interdigitated electrodes and heating coil, the platform can be tailored to print various circuits for different functionalities. The biocompatibility of the printed platform is tested using C2C12 murine myoblasts cell line. Furthermore, normal human dermal fibroblasts (primary cells) are also seeded on the platform to ascertain the compatibility.

The field of 3D printing, also known as additive manufacturing (AM), is developing rapidly in both academic and industrial research environments. New materials and printing technologies, which enable rapid and multimaterial printing, have given rise to new applications and utilizations. However, the main bottleneck for achieving many more applications is the lack of materials with new physical properties. Here, some of the recent reports on novel materials in this field, such as ceramics, glass, shape-memory polymers, and electronics, are reviewed. Although new materials have been reported for all three main printing approaches–-fused deposition modeling, binder jetting or laser sintering/melting, and photopolymerization-based approaches, apparently, most of the novel physicochemical properties are associated with materials printed by photopolymerization approaches. Furthermore, the high resolution that can be achieved using this type of 3D printing, together with the new properties, has resulted in new implementations such as microfluidic, biomedical devices, and soft robotics. Therefore, the focus here is on photopolymerization-based additive manufacturing including the recent development of new methods, novel monomers, and photoinitiators, which result in previously inaccessible applications such as complex ceramic structures, embedded electronics, and responsive 3D objects.

Background: Iatrogenic ureteral injury is an increasing concern in the laparoscopic era, affecting both patient morbidity and costs. Current techniques enabling intraoperative ureteral identification require invasive procedures or radiations. Our aim was to develop a real-time, non-invasive, radiation-free method to visualize ureters, based on near-infrared (NIR) imaging. For this purpose, we interfered with the biliary excretion pathway of the indocyanine green (ICG) fluorophore by loading it into liposomes, enabling renal excretion. In this work, we studied various parameters influencing ureteral imaging. Methods: Fluorescence intensity (FI) of various liposomal ICG sizes and doses were characterized in vitro and subsequently tested in vivo in mice and pigs. Quantification was performed by measuring FI in multiple points and applying the ureteral/retroperitoneum ratio (U/R). Results: The optimal liposomal ICG loading dose was 20%, for the different liposomes' sizes tested (30, 60, 100 nm). Higher concentration of ICG decreased FI. In vivo, the optimal liposome size for ureteral imaging was 60 nm, which yielded a U/R of 5.2 $\pm$ 1.7 (p < 0.001 vs. free ICG). The optimal ICG dose was 8 mg/kg (U/R = 2.1 $\pm$ 0.4, p < 0.05 vs. 4 mg/kg). Only urine after liposomal ICG injection had a measurable FI, and not after free ICG injection. Using a NIR-optimized laparoscopic camera, ureters could be effectively imaged in pigs, from 10 min after injection and persisting for at least 90 min. Ureteral peristaltic waves could be clearly identified only after liposomal ICG injection. Conclusions: Optimization of liposomal ICG allowed to visualize enhanced ureters in animal models and seems a promising fluorophore engineering, which calls for further developments.

Solution-based thin-film semiconductors offer a promising path for the mass production of low-cost solar cells prepared at low temperatures. Thin-film Cu-based chalcogenides such as Cu(In,Ga)(S,Se)2 (CIGSSe) and Cu2ZnSn(S,Se)4 (CZTSSe) hold great promise and have been regarded as viable candidates because of the abundance of their constituent elements and environmentally nontoxic nature. This Review summarizes the recent progress in solution-processed Cu chalcogenides (CuInSe2, Cu(In,Ga)(S,Se)2, Cu2ZnSnS4, Cu2ZnSn(S,Se)4) for thin-film solar cells, with emphasis on the precursor solution deposited by spray pyrolysis and spin coating. The general aspects, current status, and recent research highlights are introduced and analyzed in detail. Finally, the challenges and future prospects of these solar cells are also discussed.

Surface engineering is an effective method to improve the thermochromic performance of VO2. In this paper, an acid-etching top down method was proposed to tailor the VO2 surface morphology from the continuous dense-packed surface to patterned structure, which exhibited the enhanced integrated visible transmittance (Tlum) and the enlarged solar modulating abilities (ΔTsol). Moreover, a self-patterning approach was also illustrated to improve the thermochromic properties. The proposed surface engineering methods represent a facile and cost-effective approach for enhancing thermochromic properties that could promote the application of VO2 thin films in smart windows.

More than 50% of solar energy comes from the infrared region (as radiant heat) of the solar spectrum. Electrochromic (EC) materials, which can dynamically modulate the transmittance of infrared (IR) radiation, can be effectively applied in smart windows for thermal management in buildings. In this work, a core-shell TiO2-WO3 inverse opal (IO) structure was fabricated through the electrodeposition of WO3 onto TiO2 IO templates. The TiO2 IO templates were synthesized by introducing TiO2 into the voids of a polystyrene (PS) colloidal crystal template, followed by calcination to remove the PS microspheres. It was found that the TiO2-WO3 IO core-shell structure can modulate NIR transmittance at wavelengths from 700 to 1600 nm in the NIR range when potential is applied in LiClO4/PC electrolyte. When −-0.3 V is applied, up to 60% of NIR radiation in this range can be blocked. The NIR transmittance can be modulated by tuning the applied potential. This study focuses on comparing the novel TiO2-WO3 IO structure with electrodeposited WO3 thin film to fully elucidate the effect of the inverse opal morphology and the TiO2-WO3 hybrid system on the optical properties. Results show that the NIR blockage can be sustained up to 90% after 1200 reversible cycles for TiO2-WO3 IO structure. The greater surface area of the IO structure increases the number of active sites available for the redox reactions by providing a larger contact area with the electrolyte. The more electroactive area with improved charge transfer enhances the overall NIR transmittance contrast as compared to bulk WO3 thin film. Furthermore, the addition of WO3 to TiO2 to form a composite has been shown to enhance cycling performance and device lifespan.

Vanadium dioxide (VO2) is one of the most widely studied inorganic phase change material for energy storage and energy conservation applications. Monoclinic VO2 [VO2(M)] changes from semiconducting phase to metallic rutile phase at near room temperature and the resultant abrupt suppressed infrared transmittance at high temperature makes it a potential candidate for thermochromic smart window application to cut the air-condition usage. Meanwhile proper electrical potential, stable structure and good interaction with lithium ions make metastable VO2 [VO2(B)] an attractive material for fabrication of electrodes for batteries and supercapacitors. However, some long-standing issues have plagued its usage. In thermochromic application, high transition temperature (τc), low luminous transmittance (Tlum) and undesirable solar modulation ability (△Tsol) are the key problems, while in energy storage applications, short cycling lifetime and complex three-dimension microstructure are the major challenges. The common methods to produce VO2 polymorph are physical vapour deposition (PVD), chemical vapour deposition (CVD), sol-gel synthesis, and hydrothermal method. CVD is an intensively studied method due to its ability to produce uniform films with precise stoichiometry, phase and morphology control. This paper reviews the various CVD techniques to produce VO2 with controlled phases and the ternary diagram shows the relationship between film stoichiometry and various process conditions. The difference between the various CVD systems are commented and the process window to produce VO2 are tabulated. Some strategies to improve VO2′s performance in both energy conservation and energy storage applications are discussed.

The authors describe a general and facile method based on 3D printing methacrylated macromonomers to fabricate shape memory objects that can be used in flexible and responsive elec. circuits. Such responsive objects can be used in fabrication of soft robotics, minimal invasive medical devices, sensors, and wearable electronics. The use of 3D printing overcomes the poor processing characteristics of thermosets and enables complex geometries that are not easily accessible by other techniques. [on SciFinder(R)]

A platform of mechanotactic hybrids is established by projecting lateral gradients of apparent interfacial stiffness onto the planar surface of a compliant hydrogel layer using an underlying rigid substrate with microstructures inherited from 3D printed molds. Using this platform, the mechanistic coupling of epithelial migration with the stiffness of the extracellular matrix (ECM) is found to be independent of the interfacial compositional and topog. cues. [on SciFinder(R)]

Silver grids are attractive for replacing indium tin oxide as flexible transparent conductors. This work aims to improve the electrochem. stability of silver-based transparent conductors. A silver grid/PEDOT:PSS hybrid film with high cond. and excellent stability is successfully fabricated. Its functionality for flexible electrochromic applications is demonstrated by coating one layer of WO3 nanoparticles on the silver grid/PEDOT:PSS hybrid film. This hybrid structure presents a large optical modulation of 81.9% at 633 nm, fast switching, and high coloration efficiency (124.5 cm2 C-1). More importantly, an excellent electrochem. cycling stability (sustaining 79.1% of their initial transmittance modulation after 1000 cycles) and remarkable mech. flexibility (optical modulation decay of only 7.5% after 1200 compressive bending cycles) is achieved. A novel smart supercapacitor is presented that functions as a regular energy-storage device and simultaneously monitors the level of stored energy by a rapid and reversible color variation even at high current charge/discharge conditions. The film sustains an optical modulation of 87.7% and a specific capacitance of 67.2% at 10 A g-1 compared to their initial value at a c.d. of 1 A g-1. The high-performance silver grid/PEDOT:PSS hybrid transparent films exhibit promising features for various emerging flexible electronics and optoelectronic devices. [on SciFinder(R)]

In the absence of water-soluble photoinitiators with high absorbance in the ultraviolet (UV)-visible range, rapid three-dimensional (3D) printing of hydrogels for tissue engineering is challenging. A new approach enabling rapid 3D printing of hydrogels in aqueous solutions is presented on the basis of UV-curable inks containing nanoparticles of highly efficient but water-insoluble photoinitiators. The extinction coefficient of the new water-dispersible nanoparticles of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is more than 300 times larger than the best and most used commercially available water-soluble photoinitiator. The TPO nanoparticles absorb significantly in the range from 385 to 420 nm, making them suitable for use in commercially available, low-cost, light-emitting diode-based 3D printers using digital light processing. The polymerization rate at this range is very fast and enables 3D printing that otherwise is impossible to perform without adding solvents. The TPO nanoparticles were prepared by rapid conversion of volatile microemulsions into water-dispersible powder, a process that can be used for a variety of photoinitiators. Such water-dispersible photoinitiator nanoparticles open many opportunities to enable rapid 3D printing of structures prepared in aqueous solutions while bringing environmental advantages by using low-energy curing systems and avoiding the need for solvents.[on SciFinder (R)]

Cerebral malaria (CM) is a major cause of death of Plasmodium falciparum infection. Misdiagnosis of CM often leads to treatment delay and mortality. Conventional brain imaging technologies are rarely applicable in endemic areas. Here we address the unmet need for a simple, non-invasive imaging methodology for early diagnosis of CM. This study presents the diagnostic and therapeutic monitoring using liposomes containing the FDA-approved fluorescent dye indocyanine green (ICG) in a CM murine model. Increased emission intensity of liposomal ICG was demonstrated in comparison with free ICG. The Liposomal ICG’s emission was greater in the brains of the infected mice compared to naive mice and drug treated mice (where CM was prevented). Histological analyses suggest that the accumulation of liposomal ICG in the cerebral vasculature is due to extensive uptake mediated by activated phagocytes. Overall, liposomal ICG offers a valuable diagnostic tool and a biomarker for effectiveness of CM treatment, as well as other diseases that involve inflammation and blood vessel occlusion.[on SciFinder (R)]

Nanostructured thin films are important in the fields of energy conversion and storage. In particular, multi-layered nanostructured films play an important role as a part of the energy system for energy saving applications in buildings. Inkjet printing is a low-cost and attractive technol. for patterning and deposition of multi-layered nanostructured materials on various substrates. However, it requires the development of a suitable ink formulation with optimum viscosity, surface tension and evapn. rate for various materials. In this study, a versatile ink formulation was successfully developed to prep. NiO and WO3 nanostructured films with strong adhesion to ITO coated glass using inkjet printing for energy saving electrochromic applications. We achieved a high performance electrochromic electrode, producing porous and continuous electrochromic films without aggregation. The NiO film with 9 printed layers exhibits an optical modulation of 64.2% at 550 nm and a coloration efficiency (CE) of 136.7 cm2 C-1. An inkjet-printed complementary all solid-state device was assembled, delivering a larger optical modulation of 75.4% at 633 nm and a higher CE of 131.9 cm2 C-1 among all solid-state devices. The enhanced contrast is due to the printed NiO film that not only performs as an ion storage layer, but also as a complementary electrochromic layer. [on SciFinder(R)]

Single-walled carbon nanotubes (SWCNTs) are considered pivotal components for mol. electronics. Techniques for SWCNT lithog. today lack simplicity, flexibility, and speed of direct, oriented deposition at specific target locations. In this paper SWCNTs are directly drawn and placed with chem. identification and demonstrated orientation using fountain pen nanolithog. (FPN) under ambient conditions. Placement across specific elec. contacts with such alignment is demonstrated and characterized. The fundamental basis of the drawing process with alignment has potential applications for other related systems such as inorg. nanotubes, polymers, and biol. mols. [on SciFinder(R)]

The growing interest in the field of three-dimensional printing has led to great demand for new materials. In this paper we should like to present a new ink for printing porous structures that can be used for embedding various functional materials. The ink is composed of a UV polymerizable oil-in-water emulsion which converts into a solid object upon UV irradiation, and upon evaporation of the aqueous phase, forms a porous structure. The 3D objects with their various porosities, were printed by a Digital Light Processing (DLP) printer. The total surface area of the object can be controlled by changing the emulsion’s droplets size and the dispersed phase fraction. The printed 3D porous structures can be used in a variety of applications, and here we show a composite conductive object, made of silver and cross-linked polymer. After the porous object is formed, the pores are filled by vacuum, dipping in a dispersion of silver nanoparticles, followed by chemical sintering at room temperature, which results in conductive percolation paths within the 3D structure. Application of this structure is demonstrated for use as a 3D connector of an electrical circuit. [ABSTRACT FROM AUTHOR]Copyright of Journal of Materials Chemistry C is the property of Royal Society of Chemistry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder’s express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)