Local mechanical cues can affect crucial fate decisions of living cells. Transepithelial stress has been discussed in the context of epithelial monolayers, but the lack of appropriate experimental systems leads current studies to approximate it simply as an in-plane stress. To evaluate possible contribution of force vectors acting in other directions, double epithelium in a 3D-printed "GeminiChip" containing a sessile and a pendant channel is reconstituted. Intriguingly, the sessile epithelia is prone to apoptotic cell extrusion upon crowding, whereas the pendant counterpart favors live cell delamination. Transcriptome analyses show upregulation of RhoA, BMP2, and hypoxia-signaling genes in the pendant epithelium, consistent with the onset of an epithelial-mesenchymal transition program. HepG2 microtumor spheroids also display differential spreading patterns in the sessile and pendant configuration. Using this multilayered GeminiChip, these results uncover a progressive yet critical role of perpendicular force vectors in collective cell behaviors and point at fundamental importance of these forces in the biology of cancer.
This work presents the fabrication of 3D-printed composite objects based on copper(II) 1D coordination polymer (CP1) decorated with thymine along its chains with potential utility as an environmental humidity sensor and as a water sensor in organic solvents. This new composite object has a remarkable sensitivity, ranging from 0.3% to 4% of water in organic solvents. The sensing capacity is related to the structural transformation due to the loss of water mols. that CP1 undergoes with temperature or by solvent mols.′ competition, which induces significant change in color simultaneously. The CP1 and 3D printed materials are stable in air over 1 yr and also at biol. pHs (5-7), therefore suggesting potential applications as robust colorimetric sensors. These results open the door to generate a family of new 3D printed materials based on the integration of multifunctional coordination polymers with organic polymers.
Semiconductor nanocrystals have been shown to have unique advantages over traditional organic photoinitiators for polymerization in solution However, efficient photoinitiation with such nanoparticles in solvent-free and additive-free formulations so far has not been achieved. Herein, the ability to use semiconductor nanocrystals for efficient bulk polymerization as sole initiators is reported, operating under modern UV-blue-LED light sources found in 3D printers and other photocuring applications. Hybrid semiconductor-metal nanorods exhibit superior photoinitiation capability to their pristine semiconductor counterparts, attributed to the enhanced charge separation and oxygen consumption in such systems. Moreover, photoinitiation by semiconductor nanocrystals overcoated by inorganic ligands is reported, thus increasing the scope of possible applications and shedding light on the photoinitiation mechanism; in light of the results, two possible pathways are discussed - ligand-mediated and cation-coordinated oxidation A demonstration of the unique attributes of the quantum photoinitiators is reported in their use for high-resolution two-photon printing of optically fluorescing microstructures, demonstrating a multi-functionality capability. The bulk polymerization demonstrated here can be advantageous over solvent based methods as it alleviates the need of post-polymerization drying and reduces waste and exposure to toxic solvents, as well as broadens the possible use of quantum photoinitiators for industrial and research uses.
This review describes recent developments in the field of conductive nanomaterials and their application in 2D and 3D printed flexible electronics, with particular emphasis on inks based on metal nanoparticles and nanowires, carbon nanotubes, and graphene sheets. We present the basic properties of these nanomaterials, their stabilization in dispersions, formulation of conductive inks and formation of conductive patterns on flexible substrates (polymers, paper, textile) by using various printing technologies and post-printing processes. Applications of conductive nanomaterials for fabrication of various 2D and 3D electronic devices are also briefly discussed.
Renewable energy technol. and effective energy management are the most crucial factors to consider in the progress toward worldwide energy sustainability. Smart window technol. has a huge potential in energy management as it assists in reducing energy consumption of indoor lighting and air-conditioning in buildings. Electrochromic (EC) materials, which can elec. modulate the transmittance of solar radiation, are one of the most studied smart window materials. In this work, highly transparent SnO2 inverse opal (IO) is used as the framework to electrochem. deposit amorphous WO3 layer to fabricate hybrid SnO2-WO3 core-shell IO structure. The hybrid structure is capable of effective near IR (NIR) modulation while maintaining high visible light transparency in the colored and bleached states. By varying the initial diameter of the polystyrene (PS) opal template and the WO3 electrodeposition time, optimal results can be obtained with the smallest PS diameter of 392 nm and 180 s WO3 electrodeposition. In its colored state, the 392-SnO2-WO3-180 core-shell IO structure shows ≈70% visible light transparency, 62% NIR blockage at 1200 nm, and ≈15% drop in NIR blocking stability after 300 cycles. The SnO2-WO3 core-shell IO structure in this study is a promising EC material for advanced smart window technol.
Two kinds of carbon-based nanozymes were constructed from the same precursor of zeolitic imidazolate framework-8 (ZIF-8) for O2•- determination Hollow carbon cubic nanomaterial (labeled as HCC) was obtained by chem. etching ZIF-8 with tannic acid and a subsequent calcination. A porous carbon cubic nanomaterial (labeled as PCC) was prepared by directly pyrolysis. Then HCC and PCC were immobilized on the surface of screen printed carbon electrodes (SPCE), fabricating HCC and PCC modified electrodes (denoted as HCC/SPCE and PCC/SPCE). HCC/SPCE, best operated at -0.5 V (vs. Ag/AgCl), has a sensitivity of 6.55 × 102 nA μM-1 cm-2 with a detection limit of 207 nM (at S/N = 3) for O2•- sensing. And PCC/SPCE, best operated at -0.4 V (vs. Ag/AgCl), exhibited a superior performance for O2•- detection with a sensitivity of 1.14 × 103 nA μM-1 cm-2 and a low detection limit of 140 nM (at S/N = 3). The two sensors possess excellent reproducibility and stability. They were used to sense O2•- released from HeLa cells. [Figure not available: see fulltext.]
In recent years, there has been significant advancement in smart window technologies due to their effectiveness in reducing energy consumption of indoor lighting and air-conditioning in buildings. Electrochromic (EC) materials, in particular, have been widely studied as they provide a simple method for tuning or modulating visible light and IR (IR) transmittance. In this work, a novel hybrid, multi-layered SnO2-TiO2-WO3 inverse opal (IO) nanostructure has been fabricated via dip-coating and electrodeposition process. This hybrid nanostructure allows an electrochromic smart window for effective near IR (NIR) modulation, with high visible transparency and durable EC cycling stability. The visible transparency of as-fabricated hybrid multi-layered SnO2-TiO2-WO3 IO was measured to be in the range of 67.2-88.0% in the bleached state and 67.0-74.4% in the colored state, resp. Furthermore, the hybrid nanostructure is also able to modulate up to 63.6% NIR radiation at the wavelength of 1200 nm and maintain approx. 82.6% of its NIR blockage capability after 750 reversible cycles. The hybrid multi-layered SnO2-TiO2-WO3 IO nanostructure in this study can potentially be an effective and stable EC material for advanced smart window technol.
Localization of rectal tumors is a challenge in minimally invasive surgery due to the lack of tactile sensation. We had developed liposomal indocyanine green (Lip-ICG) for localization of rectal tumor. In this study we evaluated the effects of liposome size and lipid PEGylation on imaging. We used an endoscopically-guided orthotopic exptl. rectal cancer model in which tumor fluorescence was determined at different time points after i.v. (i.v.) administration of Lip-ICG and PEGylated liposomes (PEG-Lip-ICG). Signal intensity was measured by tumor-to-background ratio (TBR), or normalized TBR (compared to TBR of free ICG). Fluorescence microscopy of tumor tissue was performed to determine fluorescence localization within the tissue and blood vessels. Liposomes of 60 nm showed an increased TBR compared with free ICG at 12 h after i.v. injection: normalized TBR (nTBR) = 3.11 vs. 1, resp. (p = 0.006). Larger liposomes (100 nm and 140 nm) had comparable signal to free ICG (nTBR = 0.98 ± 0.02 and 0.78 ± 0.08, resp.), even when addnl. time points were examined (0.5, 3 and 24 h). PEG-Lip- ICG were more efficient than Lip-ICG (TBR = 4.2 ± 0.18 vs. 2.5 ± 0.12, p < 0.01) presumably because of reduced uptake by the reticulo-endothelial system. ICG was found outside the capillaries in tumor margins. We conclude that size and lipid modification impact imaging intensity.
Fabrication of devices by printing conductive interconnections on plastic substrates is of growing interest. Currently, silver flakes are wildly used, however the high cost of silver prevents their wide use in many elec. devices. A new two-step process for synthesizing thin copper flakes, and their utilization in conductive inks, is reported. In the first step, sub-micrometer copper particles are formed by thermal decomposition and self-reduction of copper formate. These copper particles are then milled in a wet bead mill that results in their transformation into thin flakes with an average thickness of 48 nm. X-ray diffraction results indicate that the copper particles undergo plastic deformation in a mechanism similar to cold rolling. The effect of various process parameters and type of dispersing agents on the morphol. and elec. performance is studied. The ink formulations result in printed patterns with 22% of bulk copper conductivity The optimal ink is used to print functioning near field communication antennas on polyimide film, which is found to have a high bending durability.
Directed-assembly by standing surface acoustic waves (SSAWs) only requires an acoustic contrast between particles and their surrounding medium. It is therefore highly attractive as this requirement is fulfilled by almost all dispersed systems. Previous studies utilizing SSAWs demonstrated mainly reversible microstructure arrangements from nanoparticles. The surface chem. of colloids dramatically influences their tendency to aggregate and sinter; therefore, it should be possible to form permanent microstructures with intimate contact between nanoparticles by controlling this property. Dispersed silver nanoparticles in a microfluidic channel were exposed to SSAWs and reversibly accumulated at the pressure nodes. We show that addition of chloride ions that remove the polyacrylic capping of the nanoparticles trigger their sintering and the formation of stable conducting silver microstructures. Moreover, if the destabilizing ions are added prior to nanoparticle assembly while continuously streaming the dispersion through the acoustic aperture, the induced aggregation leads to formation of significantly thinner microstructures, which are (for the first time) unlimited in length by the acoustic apparatus This new approach overcomes the discrepancy between the need for organic dispersants to prevent unwanted aggregation in the dispersion, and the end product's requirement for intimate contact between the colloidal particles.
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)]