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- 2018
- microfabrication
- annealing
- microactuators
- bimorph
- lift-off resist
- electron beam evaporation
- XeF2 dry etching
- NiTi
- x-ray diffraction
- shape memory alloy
- Materials Science and Engineering
- Northwestern Polytechnical University
- Brookhaven National Laboratory
- Stevens Institute of Technology
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Simultaneous Measurement of Refractive Index and Temperature Based on a Peanut-Shape Structure In-Line Fiber Mach–Zehnder Interferometer
摘要： We proposed a peanut-shape structure in-line fiber Mach–Zehnder interferometer (MZI) for simultaneous measurement of refractive index (RI) and temperature. Two kinds of demodulation methods were investigated and compared. The wavelength-related and phase-related character matrices of the in-line fiber MZI were determined for simultaneous measurement of RI and temperature, respectively. For the wavelength-related measurement, the highest temperature and RI sensitivities were 0.0709 nm/°C and ?47.3620 nm/RIU, respectively. The phase-related measurement was with a lower measuring errors compared to the wavelength-related measurement, and the highest temperature and RI sensitivities were ?0.0632rad/°C (0.0764 nm/°C) and 77.0995rad/RIU (?93.2429 nm/RIU), respectively. The minimum measuring errors of temperature and RI were 0.3800 °C and 0.0004 RIU, respectively.
关键词： Mach–Zehnder interferometer,simultaneous measurement of refractive index and temperature,Optical fiber sensor,peanut-shape structure
更新于2025-11-28 14:23:57
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Fiber Brag grating monitoring of a morphing wing based on a polyvinyl chloride reinforced silicone substrate
摘要： Here, the three-dimensional (3D) shape monitoring of polyvinyl chloride (PVC)-reinforced silicone substrate for a morphing wing is detailed, using Fiber Bragg grating (FBG) sensors. An optical ?ber FBG sensor was embedded into a soft silicone substrate, which was glued onto the surface of a PVC substrate. This substrate was aligned with the morphing wing’s ?exible ribs of the. Sensing experiments were carried out both with and without the PVC reinforced silicone substrate, and the sensitivity and repeatability of the two sensors were compared. The PVC-reinforced silicone substrate sensor was calibrated using standard curvature calibration blocks to obtain a relationship between wavelength shift and the bending curvature of the PVC-reinforced silicone substrate, and the wing shape was reconstructed at di?erent deformation states. Several wing shapes were also reconstructed using a precise visual measurement system. Comparing the FBG sensing method with this visual measurement system demonstrated the e?ectiveness of the FBG method proposed here. Its maximum error was < 3%, so it can successfully sense the shape of a PVC-reinforced silicone substrate for morphing wing. The FBG sensing method therefore has potential for applications in shape monitoring in the ?elds of soft robotics and ?exible biosensor monitoring.
关键词： PVC reinforce silicone substrate,Wing shape monitoring,Soft sensor,FBG sensing
更新于2025-11-28 14:23:57
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Opposite Self-Folding Behavior of Polymeric Photoresponsive Actuators Enabled by a Molecular Approach
摘要： The ability to obtain 3D polymeric objects by a 2D-to-3D shape-shifting method is very appealing for polymer integration with different materials, from metals in electronic devices to cells in biological studies. Such functional reshaping can be achieved through self-folding driven by a strain pattern designed into the molecular network. Among polymeric materials, liquid crystalline networks (LCNs) present an anisotropic molecular structure that can be exploited to tailor internal strain, resulting in a natural non-planar geometry when prepared in the form of flat films. In this article, we analyze the influence of different molecular parameters of the monomers on the spontaneous shape of the polymeric films and their deformation under different stimuli, such as heating or light irradiation. Modifying the alkilic chains of the crosslinkers is a simple and highly effective way to increase the temperature sensitivity of the final actuator, while modifying ester orientation on the aromatic core interestingly acts on the bending direction. Combining such effects, we have demonstrated that LCN stripes made of different monomeric mixtures originate complex non-symmetric deformation under light activation, thus opening up new applications in photonic and robotics.
关键词： photonic actuators,liquid crystalline networks,curvature design,photoresponsive polymers,shape-changing materials
更新于2025-11-21 11:24:58
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Band gap engineered zinc oxide nanostructures <i>via</i> a sol–gel synthesis of solvent driven shape-controlled crystal growth
摘要： A reliable sol–gel approach, which combines the formation of ZnO nanocrystals and a solvent driven, low shape-controlled, crystal-growth process to form well-organized ZnO nanostructures at temperature is presented. The sol of ZnO nanocrystals showed shape-controlled crystal growth with respect to the solvent type, resulting in either nanorods, nanoparticles, or nanoslates. The solvothermal process, along with the solvent polarity facilitate the shape-controlled crystal growth process, augmenting the concept of a selective adhesion of solvents onto crystal facets and controlling the final shape of the nanostructures. The XRD traces and XPS spectra support the concept of selective adhesion of solvents onto crystal facets that leads to yield different ZnO morphologies. The shift in optical absorption maxima from 332 nm in initial precursor solution, to 347 nm for ZnO nanocrystals sol, and finally to 375 nm for ZnO nanorods, evidenced the gradual growth and ripening of nanocrystals to dimensional nanostructures. The engineered optical band gaps of ZnO nanostructures are found to be ranged from 3.10 eV to 3.37 eV with respect to the ZnO nanostructures formed in different solvent systems. The theoretical band gaps computed from the experimental XRD spectral traces lie within the range of the optical band gaps obtained from UV-visible spectra of ZnO nanostructures. The spin-casted thin film of ZnO nanorods prepared in DMF exhibits the electrical conductivity of 1.14 × 10?3 S cm?1, which is nearly one order of magnitude higher than the electrical conductivity of ZnO nanoparticles formed in hydroquinone and ZnO sols. The possibility of engineering the band gap and electrical properties of ZnO at nanoscale utilizing an aqueous-based wet chemical synthesis process presented here is simple, versatile, and environmentally friendly, and thus may applicable for making other types of band-gap engineered metal oxide nanostructures with shape-controlled morphologies and optoelectrical properties.
关键词： electrical conductivity,ZnO nanostructures,optical band gap,shape-controlled crystal growth,sol–gel synthesis
更新于2025-11-19 16:56:42
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Influence of bath temperatures on physical and electrical properties of potentiostatically deposited Cu2O thin films for heterojunction solar cell applications
摘要： In the present work, the influence of bath temperatures on structural, morphological, vibrational, optical, electrical and photo response properties of the electrochemically deposited cuprous oxide (Cu2O) thin films on fluorine doped tin oxide substrate is extensively investigated with the help of X-ray diffraction (XRD), scanning electron microscopy (SEM), Micro Raman spectroscopy, photo luminescence (PL) spectroscopy, UV–visible spectroscopy, LCR measurement, Keithley 4200 semiconductor characterization system respectively. XRD patterns reveal that the deposited Cu2O films have cubic structure grown along the preferential (111) orientation and the film deposited at 40 °C shows better crystalline nature when compared at 55 and 70 °C. The micro structural properties of films such as crystallite size (D), dislocation density (δ), micro strain (ε) and stacking fault probability (α) were calculated and discussed in detail. SEM displays a well-defined three side pyramid shaped morphology for the film deposited at 40 °C. Micro Raman and PL spectra reveal the film deposited at 40 °C by being better crystalline at a higher acceptor concentration. UV–Visible study shows that the optical energy band gap increases from 2.05 to 2.17 eV with an increase in bath temperature from 40 to 70 °C. The frequency-temperature dependence of impedance analysis shows a higher electrical conductivity for a film deposited at 40 °C compared to other bath temperatures. I-V measurement illustrates a good photoconductivity response for Cu2O thin film deposited at 40 °C compared to films deposited at 55 and 70 °C.
关键词： Micro Raman spectroscopy,X-ray diffraction,Photoconductivity,Cuprous oxide,Pyramid shape
更新于2025-11-19 16:46:39
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Facile synthesis of yellow emissive carbon dots with high quantum yield and their application in construction of fluorescence-labeled shape memory nanocomposite
摘要： Synthesizing carbon dots (CDs) with efficient long-wavelength emissions (i.e., yellow- to red light) generally suffer from sophisticated approaches, time-consuming process, harsh conditions, and requirement of organic solvent; also, a further limitation of the resulting CDs is relatively low quantum yield (QY) in aqueous solution. Herein, novel yellow emitting CDs (Y-CDs) with a considerable QY of 62.8% were synthesized from a precursor comprising resorcinol and o-phenylenediamine via a facile microwave method. To probe the fluorescence mechanism, another typical resorcinol-derived CDs using ethylenediamine as dopant were fabricated as well, showing strong green emission with an absolute QY of 60.6%. Spectroscopic and structural characterizations indicated that the distinct redshift of green to yellow emission depended on the dimension of conjugated sp2-domain and the content of graphitic N heavily, while the excellent QY was highly related to the low proportion of defective sp2 carbon cluster and high nitrogen content within CDs. Moreover, the Y-CDs were confirmed to be capable of introducing additional crosslinking points in poly(vinyl alcohol) (PVA) polymer, which resulted in the Y-CDs-contained nanocomposite behaving superior and tunable water-induced shape recovery performances. Importantly, since being labeled with long-wavelength emission, the responsiveness of PVA/Y-CDs composite will contribute to its versatile utilization in biology-relevant fields.
关键词： shape recovery,fluorescence mechanism,yellow emission,carbon dots,nanocomposite
更新于2025-11-14 15:23:50
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Scaling effects on the optical properties of patterned nano-layered shape memory films
摘要： Nano-layered films of PVAc/PU systems were fabricated by forced assembly coextrusion method. The bulk shape memory properties of PVAc/PU systems were utilized to program nanoscale patterns such as diffraction grating which exhibit iridescence after patterning. A hot embossing process has been utilized to imprint diffraction grating patterns as nano-scale information onto the surface of the thin multilayer films. Three levels of hierarchy i.e. layer thickness, spacing and heights of patterns, governs the functionality of the patterned multilayer film. The time and temperature dependent viscoelastic shape memory behavior determines the opto-mechanical tunability of the film. Mechanical switching of the patterns also leads to optical switching of the films which corresponds to their efficiency of information retrieval. The recovery of patterns as well as the diffractive property depends on the layer thickness (l) of films and heights of patterns (h0). The results illustrate that the higher ratio of h0/l better is the recovery of the grating patterns and the corresponding diffractive properties. This scaling effect enables versatile applications in information security by tuning the layer structure of the multilayer shape memory films.
关键词： scaling effect,shape memory film,pattern programming,hot embossing,multilayer film,information security,diffractive optical element,thermal responsive optics
更新于2025-10-22 19:40:53
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Anomalous shape evolution of Ag2O2 nanocrystals modulated by surface adsorbates during electron beam etching
摘要： An understanding of nanocrystal shape evolution is significant for the design, synthesis and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with high spatial resolution. Here, we report the anomalous shape evolution of Ag2O2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag2O2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag2O2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag2O2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Our findings provide critical insights into the modulatory function of surface adsorbates on shape control of nanocrystals.
关键词： surface adsorbates,Ag2O2 nanocrystal,shape evolution,In situ TEM,electron beam etching
更新于2025-09-23 15:23:52
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Preparation of Monodispersed Nanoparticles of Transparent Conductive Oxides
摘要： Generally, indium-tin-oxides (ITO) thin film is prepared by the sputtering process with ITO target, but only 20 % of ITO yielded from the target is deposited on the substrate. Namely, about 80 % ITO is exhausted by the deposition elsewhere far from the substrate. The recycling process of indium is limited so that ca. 20 % ITO of the starting material is lost without any recovery. Even if the recycling of ITO has been carried out in this process, we should prepare ITO target of 5 times more than apparent use of ITO on film. If we change it to printing process from the sputtering, the reduction in ITO use is expected as ca. 50 %, considering the increase in film thickness by printing. Our target technology also includes ITO nanoink for the project. As a result, monodispersed ITO nanoparticles (NPs) with a cubic shape were fabricated by using quaternary ammonium hydroxide-assisted metal hydroxide organogels. These NPs have perfect uniformity in size with beautiful shape, and perfect single crystalline structure including Sn. As we were attempted to make thin film with ITO nanoink, it was successfully fabricated below 200 nm in thickness and the resistivity was drastically decreased below 1.0 × 10–3 Ω cm after heat treatments. GZO nanoink as substitute of ITO has also been developed.
关键词： indium tin oxide,transparent conductive oxides,uniform nanoparticles,shape control
更新于2025-09-23 15:23:52
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Synthesis, characterization and comparative studies of nonlinear optical chromophores with rod-like, Y-shaped and X-shaped configurations
摘要： A series of highly polarizable nonlinear optical (NLO) chromophores ZJ1-4 with three different configurations, including rod-like, Y-shaped and X-shaped configurations, have been synthesized with facile routes and systematically studied. The resulted chromophores exhibited excellent thermal stabilities. The relationship between molecular configuration and NLO activity was analyzed from the theoretical calculation and experiment. The molecular dipole moment of chromophore ZJ4 was enhanced by X-shaped structure with two acceptors. Meanwhile, the tendency of forming anti-parallel interactions could be inhibited by disk-like molecular configuration with larger steric hindrance. ZJ4 exhibits the largest EO activity of 103 pm/V, and both of molecular and material NLO properties are improved for the chromophore ZJ4 with the X-shaped configuration compared with corresponding benchmark chromophore ZJ1 with rod-like molecular structure.
关键词： shape,nonlinear optic,electro-optic,structure-property relationship,chromophores
更新于2025-09-23 15:23:52