Silver nanoparticle based microelectrodes embedded between layers of hydrogel material were successfully fabricated. 3D bioprinting is employed to print the entire bioelectronics platform comprising of conducting silver ink and Gelatin methacryloyl (GelMA) hydrogel. The additive manufg. technique of bioprinting gives design freedom for the circuit, saves material and shortens the time to fabricate the bioelectronics platform. The silver platform shows excellent elec. cond., structural flexibility and stability in wet environment. It is tested for biocompatibility using C2C12 murine myoblasts cell line. The work demonstrates the potential of the fabricated platform for the realization of practical bioelectronic devices. [on SciFinder(R)]

Transparent conductive networks are important for flexible electronics and solar cells. Often interwire (junction) cond. is the limiting factor for network cond. and can be improved by various treatments. The cond. of individual junctions in a single walled carbon nanotube network was measured by conductive at. force microscopy before and after exposure to nitric acid. The measurements show that this exposure improves the cond. of each one of the junctions within the network. The results suggest that the acid improves the cond. by p-type charge transfer doping and by surfactant degrdn. [on SciFinder(R)]

Perovskite solar cells have emerged as a new semi-transparent PV technol. for urban infrastructures that demands an explicit trade-off between power conversion efficiency (PCE) and av. visible transparency (AVT) which can be adjusted by various modifications in the absorber layer. Here, we introduce a scalable and facile "one and a half" step deposition route for mixed cation perovskites patterned in a sub-micron sized grid structure for semi-transparent solar cells. The initial perovskite phase is formed in one step using a grid pattern, while the addnl. step involves dipping of the pre-deposited perovskite grid in a hot soln. of formamidinium iodide (FAI) in isopropanol (IPA). Detailed anal. suggests that the addnl. step increases pore filling, crystal quality, and grain size and lowers the content of residual PbI2 as well as reveals improved photo phys. properties. An av. PCE ∼10% with an AVT of 28% is attained with a gold contact for the champion semi-transparent solar cell. The proposed deposition route can be generalized for all other types of perovskite based devices to yield better efficiency. [on SciFinder(R)]

More than 50% of solar energy comes from the IR region (as radiant heat) of the solar spectrum. Electrochromic (EC) materials, which can dynamically modulate the transmittance of IR (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 morphol. 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 no. 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 addn. of WO3 to TiO2 to form a composite has been shown to enhance cycling performance and device lifespan. [on SciFinder(R)]

A sol, aq. soln.-based ink is presented for fabrication of 3D transparent silica glass objects with complex geometries, by a simple 3D printing process conducted at room temp. The ink combines a hybrid ceramic precursor that can undergo both photopolymn. reaction and a sol-gel process, both in a soln. form, without any particles. The printing is conducted by localized photopolymn. with the use of a low-cost 3D printer. Following printing, upon aging and densifying, the resulting objects convert from a gel to a xerogel and then to a fused silica. The printed objects, which are composed of fused silica, are transparent and have tunable d. and refractive indexes. [on SciFinder(R)]

3D printed electronics is an emerging field of high importance in both academic research and industrial manufg. It enables fabrication of 3D devices with embedded or conformal electronic circuits, which are relevant to a variety of applications, such as Internet of things, soft robotics, and medical devices. Patterning of elec. conductors with cond. higher than 50% bulk copper is challenging and usually involves electroless or electrolytic deposition processes that require the use of very costly catalyst, mainly palladium, as a seed material. Here, the use of a binuclear copper complex as a very efficient replacement for the conventional catalysts, which can be directly inkjet printed onto 3D plastic objects, is described. After printing, the copper complex is converted into pure copper upon short exposure to low-temp. plasma. By combining the binuclear complex with electroless plating, resistivity as low as 2.38 μΩ cm, which corresponds to a 72% cond. of bulk copper, is obtained. The applicability of the complex ink and the process is demonstrated in the fabrication of a near-field communication antenna on a 3D printed plastic object. [on SciFinder(R)]

Transparent conductive networks are important for flexible electronics and solar cells. Often interwire (junction) cond. is the limiting factor for network cond. and can be improved by various treatments. The cond. of individual junctions in a single walled carbon nanotube network was measured by conductive at. force microscopy before and after exposure to nitric acid. The measurements show that this exposure improves the cond. of each one of the junctions within the network. Our results suggest that the acid improves the cond. by p-type charge transfer doping and by surfactant degrdn. [on SciFinder(R)]

High-quality patterns were successfully prepd. by inkjet-printing WO3-PEDOT:PSS composites on different substrates including the rigid FTO glass and most importantly, on flexible PEDOT:PSS/Ag grid/PET. Excellent electrochromic performances can be achieved, including large optical modulation (85.7% optical contrast at the wavelength of 633nm on FTO glass substrate), fast switching speed (coloration/bleaching time of 2.4/0.8s on the PEDOT:PSS/Ag grid/PET substrate), instantaneous coloration efficiency (68.8cm2 C-1) and good cycling stability (up to 10,000 cycles). The effects of the applied potential window during electrochem. evaluation on the electrochromic performances were analyzed in detail. The printed electrochromics films on PEDOT:PSS/Ag grid/PET showed the best electrochem. stability, in agreement with its superior cond. and transmittance at 633nm of 0.6Ω/sq and 66%, resp. It sustained transmittance modulation of about 75.5% and 53.1% of its first cycle recorded contrast at 633nm, after being subjected to 1000 and 5000 cycles, resp., and maintained good electrochem. stability up to 10,000 cycles. Moreover, a robust mech. stability was also achieved by the printed films on flexible PEDOT:PSS/Ag grid/PET substrate. The film maintained a transmittance modulation of 85.8% of its original contrast after 5000 bending cycles at a curvature radius of 1cm. The inkjet-printed WO3 nanocomposite based flexible electrochromic displays exhibited excellent electrochromic performance, making it a promising candidate for energy efficient displays, e-books, e-cards and multifunctional electronic devices. [on SciFinder(R)]

We report on new material compns. enabling fully printed mechanoluminescent 3D devices by using a one-step direct write 3D printing technol. The ink is composed of PDMS, transition metal ion-doped ZnS particles, and a platinum curing retarder that enables a long open time for the printing process. 3D printed mechanoluminescent multi-material objects with complex structures were fabricated, in which light emission results from stretching or wind blowing. The multi-material printing yielded anisotropic light emission upon compression from different directions, enabling its use as a directional strain and pressure sensor. The mechanoluminescent light emission peak was tailored to match that of a perovskite material, and therefore, enabled the direct conversion of wind power in the dark into electricity, by linking the printed device to perovskite-based solar cells. [on SciFinder(R)]

We report a method to prep. highly stretchable and UV curable hydrogels for high resoln. DLP based 3D printing. Hydrogel solns. were prepd. by mixing self-developed high-efficiency water-sol. TPO nanoparticles as the photoinitiator with an acrylamide-PEGDA (AP) based hydrogel precursor. The TPO nanoparticles make AP hydrogels UV curable, and thus compatible with the DLP based 3D printing technol. for the fabrication of complex hydrogel 3D structures with high-resoln. and high-fidelity (up to 7 μm). The AP hydrogel system ensures high stretchability, and the printed hydrogel sample can be stretched by more than 1300%, which is the most stretchable 3D printed hydrogel. The printed stretchable hydrogels show an excellent biocompatibility, which allows us to directly 3D print biostructures and tissues. The great optical clarity of the AP hydrogels offers the possibility of 3D printing contact lenses. More importantly, the AP hydrogels are capable of forming strong interfacial bonding with com. 3D printing elastomers, which allows us to directly 3D print hydrogel-elastomer hybrid structures such as a flexible electronic board with a conductive hydrogel circuit printed on an elastomer matrix. [on SciFinder(R)]

The field of 3D printing, also known as additive manufg. (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 phys. 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 photopolymn.-based approaches, apparently, most of the novel physicochem. properties are assocd. with materials printed by photopolymn. approaches. Furthermore, the high resoln. 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 photopolymn.-based additive manufg. 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. [on SciFinder(R)]

Liquid drop evaporation on surfaces is present in many industrial and medical applications, e.g., printed electronics, spraying of pesticides, DNA mapping, etc. Despite this strong interest, a theoretical description of the dynamic of the evaporation of complex liquid mixtures and nanosuspensions is still lacking. Indeed, one of the aspects that have not been included in the current theoretical descriptions is the competition between the kinetics of evaporation and the adsorption of surfactants and/or particles at the liquid/vapor and liquid/solid interfaces. Materials formed by an electrically isolating solid on which a patterned conducting layer was formed by the deposits left after drop evaporation have been considered as very promising for building electrical circuits on flexible plastic substrates. In this work, we have done an exhaustive study of the evaporation of nanosuspensions of latex and hydrophobized silver nanoparticles on four substrates of different hydrophobicity. The advancing and receding contact angles as well as the time dependence of the volume of the droplets have been measured over a broad range of particle concentrations. Also, mixtures of silver particles and a surfactant, commonly used in industrial printing, have been examined. Furthermore, the adsorption kinetics at both the air/liquid and solid/liquid interfaces have been measured. Whereas the latex particles do not adsorb at the solid/liquid and only slightly reduce the surface tension, the silver particles strongly adsorb at both interfaces. The experimental results of the evaporation process were compared with the predictions of the theory of Semenov et al. (Evaporation of Sessile Water Droplets: Universal Behavior in the Presence of Contact Angle Hysteresis. Colloids Surf. Physicochem. Eng. Asp. 2011, 391 (1-3), 135-144) and showed surprisingly good agreement despite that the theory was developed for pure liquids. The morphology of the deposits left by the droplets after total evaporation was studied by scanning electronic microscopy, and the effects of the substrate, the particle nature, and their concentrations on these patterns are discussed.[on SciFinder (R)]

The trend of developing electrochem. 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 technol. to fabricate electrodes to make some improvements. Highly conductive Ag nanoparticles based electrodes were obtained on plastic substrate by inkjet printing technol. followed by a sintering process at room temp. The resistivity of IPAgE is detd. to be 64.0 ± 5.3 μΩ cm. With better cond. and the nanoparticle-based interface, superb electrochem. 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 electrochem. sensors. [on SciFinder(R)]

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 ± 1.7 (p < 0.001 vs. free ICG). The optimal ICG dose was 8 mg/kg (U/R = 2.1 ± 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.[on SciFinder (R)]

During decompn. of copper formate, a volatile intermediate is formed, that can be utilized to fabricate conductive copper lines for elec. interconnections. By the method called Reactive Transfer Printing (RTP), a pattern of copper (II) formate was printed, and placed adjacent to a second surface; decompn. of the printed pattern led to a transfer of copper to the second substrate. It was found that the yield of the transfer process improved due to presence of several carboxylic acids which are liq. with a high b.p. Furthermore we found that the transport of copper starts at a lower temp. than previously reported, indicating that the first decompn. step of copper formate is related to the catalytic decompn. of formic acid on a copper surface. The findings enable printing of conductive copper patterns onto the interior surface of a glass vessel. [on SciFinder(R)]

Liq. drop evapn. on surfaces is present in many industrial and medical applications, e.g., printed electronics, spraying of pesticides, DNA mapping, etc. Despite this strong interest, a theor. description of the dynamic of the evapn. of complex liq. mixts. and nanosuspensions is still lacking. Indeed, one of the aspects that have not been included in the current theor. descriptions is the competition between the kinetics of evapn. and the adsorption of surfactants and/or particles at the liq./vapor and liq./solid interfaces. Materials formed by an elec. isolating solid on which a patterned conducting layer was formed by the deposits left after drop evapn. have been considered as very promising for building elec. circuits on flexible plastic substrates. In this work, we have done an exhaustive study of the evapn. of nanosuspensions of latex and hydrophobized silver nanoparticles on four substrates of different hydrophobicity. The advancing and receding contact angles as well as the time dependence of the vol. of the droplets have been measured over a broad range of particle concns. Also, mixts. of silver particles and a surfactant, commonly used in industrial printing, have been examd. Furthermore, the adsorption kinetics at both the air/liq. and solid/liq. interfaces have been measured. Whereas the latex particles do not adsorb at the solid/liq. and only slightly reduce the surface tension, the silver particles strongly adsorb at both interfaces. The exptl. results of the evapn. process were compared with the predictions of the theory of Semenov et al. (Evapn. of Sessile Water Droplets: Universal Behavior in the Presence of Contact Angle Hysteresis. Colloids Surf. Physicochem. Eng. Asp. 2011, 391 (1-3), 135-144) and showed surprisingly good agreement despite that the theory was developed for pure liqs. The morphol. of the deposits left by the droplets after total evapn. was studied by scanning electronic microscopy, and the effects of the substrate, the particle nature, and their concns. on these patterns are discussed. [on SciFinder(R)]

A printable hybrid hydrogel is fabricated by embedding poly(N-isopropylacrylamide) (PNIPAm) microparticles within a water-rich silica-alumina(Si/Al)-based gel matrix. The hybrid gel holds water content of up to 70 wt%, due to its unique Si/Al matrix. The hybrid hydrogel can respond to both heat and elec. stimuli, and can be directly printed layer-by-layer using a com. 3-dimensional printer, without requiring any curing. The hybrid ink is printed onto a transparent, flexible conductive electrode composed of silver nanoparticles and sustains bending angles of up to 180°, which enables patterning of various flexible devices such as smart windows and a 3D optical waveguide valve. [on SciFinder(R)]

Metal-org. frameworks (MOFs) are a well-developed field of materials, having a high potential for various applications such as gas storage, water purifn., and catalysis. Despite the continuous discoveries of new MOFs, so far there are only a limited no. of industrial applications, partially due to their low chem. stability and limited mech. 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 matrixes for columns and flow reactors, will open the way for utilization of this important class of materials. [on SciFinder(R)]