Applied Research最新文献

Academic translational research efforts to industry are often an underlying sought-after goal among various researchers. Through the interchanges of research endeavors between academia-industry, great innovations can/has been achieved that cater to the real-world application by bridging “industrially relevant” problem solving with pursuing fundamental studies. It is pertinent that most of the studies from university-level research works may not translate into demonstrable market products due to various reasons. Funding support, individual researcher goals, socioeconomic factors, and most importantly the technical know-how of generating revenue strategies for startups, are a few of the factors that have slowed the pace of collaborative efforts. However, we believe that the most crucial component is the identification of the critical parameters that solve long-standing problems that hinder the scale-up of the lab scale research into marketable products considering the techno-economic analysis. To illustrate this, we take the three most relevant examples of devices for fuel generation, devices to utilize solar radiation, and devices for detection and other related applications. In this perspective, we provide an in-depth case study of each of these critical parameters to comment on the direction of research avenues that can serve as step-stones for the commercialization of university-level lab research studies.

Silicon epitaxy is an essential building block in the manufacturing of complementary metal-oxide semiconductor (CMOS) devices. Accurate determination of epitaxial layer thickness is indispensable for a uniform and reproducible process. In this paper, we compare thickness values of the transition zone (TZ) in silicon epitaxial wafers obtained by two of Semilab's production-compatible electrical and optical characterization techniques: Fourier-transform infrared (FTIR) reflectometry and spreading resistance profiling (SRP). We demonstrate a high correlation between TZ thicknesses obtained from the optical modeling of FTIR reflectance spectra and SRP profiles. The dependence of TZ thickness change on the high-temperature annealing steps is also examined. FTIR reflectometry thus offers a quick, contactless alternative for obtaining structural parameters of an epitaxial layer, and these values can be well matched to those given by SRP.

Cadmium telluride is an efficient light absorbing material successfully used in solar cell technology. The efficiency of such photovoltaic devices is strongly dependent on post-deposition thermal treatments in the presence of chlorine. The benefits of this process on the absorbing layer include removal of intragrain defects, grain growth enhancement, and grain boundaries passivation. The absorber chlorination is a crucial step for which CdCl₂ is the most common choice. Its use, however, has been overshadowed by the toxicity of Cd- and Cl-containing vapors and residues. In this work, chlorine was incorporated in CdTe films during growth using sputtering targets with different chloride compounds: CdCl₂, TeCl₄, BaCl₂, CaCl₂, or LiCl. After characterizing these films, CdTe:CdCl₂ and CdTe:TeCl₄ were selected as feasible absorbers for testing their performance in photovoltaic devices. Efficiencies near 7% were obtained in as-grown unoptimized cells in which the absorber consisted of two layers: pristine CdTe and CdTe:CdCl₂ or CdTe:TeCl₄. The chlorinated layers acted as Cl sources for the adjacent CdTe and CdS, which produced a homogeneous distribution of chlorine throughout the cell. In the during-growth activating-layer (DG-AL) method used here, the chlorine diffusion during growth had a doping effect, passivated grain boundaries and defects, improved the back contact characteristics by reducing the CdTe work function, and lowered the pinhole formation probability by producing a compact chlorinated CdTe layer.

Geopolymers (GPs) are emerging, low-density ceramic materials that are simple to manufacture, with high elastic modulus and strength, albeit with low toughness. Fiber reinforcements have been used to achieve varied ductile behaviors, but little is known about the GP addition to polymeric frame structures. Thus, drawing inspiration from the nanostructure of bones, this paper investigated an interpenetrating, co-continuous composite consisting of a GP as the stiff but brittle phase, and a 3D-printed polymer (PA12 White) as the soft and deformable phase. The composite mechanical properties and failure modes were studied experimentally using uniaxial compression and four-point bending tests. The co-continuous network constrained brittle cracking within the GP and reduced strain localization in the polymer. The results showed that the composite had higher strength (56.11 ± 2.12 MPa) and elastic modulus (6.08 ± 1.37 GPa) than the 3D-printed polymer and had higher toughness (5.98 ± 0.24 MJ/mm³) than the GP for the specific geometries examined. The shape effect study demonstrated that cubic structures had higher elastic modulus and strength but at the expense of lower toughness when compared to rectangular prism structures. The study of scale effects indicated that increasing the number of periodic unit cells while maintaining consistent bulk dimensions led to augmented strength and toughness, albeit without statistically significant alterations in elastic modulus. Thus, this paper presents an experimental realization of a novel, bio-inspired, interpenetrating, GP–polymer composite design, offering improved strength and toughness. It also provides valuable insights into the shape and size effects on the mechanical properties of this new composite.

The biggest obstacles in treating cancer with traditional chemotherapy are unpleasant side effects and drug resistance. A growing amount of interest has been exhibited in using aptamers as target ligands for targeted cancer therapy and specific cancer cell identification due to their distinct benefits. Aptamer-conjugated nano-materials have recently provided new prospects in cancer treatment with their improved therapeutic efficacy and capability of reducing toxicity. Consequently, they are not perceived as alien substances our body, which allows their comfortable acceptance. Several tumor markers such as nucleolin, mucin, and the epidermal growth factor receptor can be effectively recognized by aptamers. In addition, glycoproteins on the surface of tumor cells can be recognized using aptamers. So surface modification of drug by aptamer are accomplished for enhanced tumor-specific recognition by which drug-specific accretion, internalization, and drug retention in tumors increased through specific ligand-mediated interactions and thus therapeutic index is increased. Here, we highlight some promising classes of aptamer-conjugated nanoparticles for the specific recognition of cancer cells and targeted drug delivery and the molecular mechanism and immunomodulatory regulation of these aptamer have been focused.

For the manufacture of extrusion dies, three-dimensional (3D) printing with photopolymers offers numerous advantages including flexibility, high surface quality, decent build speed, low costs and a reduced amount of waste. However, the majority of photocurable resins used in vat photopolymerization 3D printing rely on acrylates, which entail 3D-printed objects with poor mechanical properties. In particular, the high brittleness limits their application in rapid tooling, for which tough materials with high glass transition temperatures (T_g) are required. In the present study, we highlight the use of dual curable acrylate-epoxy resins with dynamic covalent bonds for the direct fabrication of extrusion dies. During digital light processing (DLP) 3D printing the acrylate network is formed, whose toughness and thermal stability are significantly enhanced by the thermoactivated formation of a second network. By following a postbaking procedure, aminoglycidiyl monomers are cured with an anhydride hardener bearing bulky norbornene groups yielding interpenetrating polymer networks with a T_g > 100°C. The tertiary amine groups present in the structure of the aminoglycidyl derivatives do not only accelerate the ring-opening reaction but also act as internal catalysts and activate bond exchange reactions between free –OH groups and ester moieties available in the photopolymer. This is confirmed by rheometer studies showing a distinctive stress relaxation at elevated temperature and giving rise to a possible reprocessability of the 3D-printed dies. With a selected resin formulation, a set of dies is printed by DLP 3D printing, with which a highly filled rubber compound is successfully extruded. The results clearly show that dual curable resins with dynamic covalent bonds are a promising class of material for rapid tooling and pave the way towards a customized and convenient fabrication of extrusion dies for rubber processing.

Today, controlling the photopolymerization process during the 3D printing in vat photopolymerization is a key challenge. In this work, it is shown that using a relatively limited set of parameter, it is possible to estimate key factors involved in such process. On the basis of 16 formulations containing different concentrations of photoinitiator and UV filter, attempt was made to rationalize the photonic parameters used in the 3D printing process, that is, the depth of penetration Dp and the critical energy Ec. It is shown that the experimental Dp values can be correlated with calculated ones from Bouguer–Beer–Lambert law. Real-time Fourier-transform infrared spectroscopy (RT-FTIR) experiments were performed under similar conditions as in 3D printing. The conversion profiles were used to estimate the Ec values. The limits of this approach was discussed as a function of the UV filter concentration. Finally, the RT-FTIR curves are exploited to predict the in-depth conversion of the different 3D printed layers and compared to experimental results obtained by confocal Raman microscopy.

Intelligent packaging has attracted research interest during the last decades. More specifically, food packaging is of great importance due to the utmost need to monitor and maintain food quality until consumption. Thus, there is a high demand for sensors capable of detecting gases such as CO₂, emitted by packaged meat or chicken which serve as freshness indicators. In the present work, a sensor based on Cu₂O nanocubes was fabricated and tested against CO₂ at room temperature. Cu₂O nanocubes were synthesized by solution-based methods and deposited on commercial interdigitated electrodes. Specifically, the Cu₂O-based sensor successfully detected down to 5% CO₂ (50,000 ppm) in the ambient atmosphere, at room temperature, with a response time of less than 90 s. This level of CO₂ is in the range that indicates the unsuitability of packaged meat for consumption. Furthermore, the sensor was able to maintain its response to CO₂ after being stored in the fridge for 20 days, showcasing its endurance under food maintenance conditions.

Carbon nanotubes (CNTs) have attracted interest for optoelectronic applications due to their unique electronic and optoelectronic properties. In particular, multiwall (MW) CNTs film acts as perfect photo-collector surface with the possibility to tune the absorbance by controlling the film thickness. In this work, we demonstrate two types of hybrid Si-MWCNTs photodetectors. The MWCNTs are solution-processed and deposited on n-silicon substrate covered by two different dielectrics (Si₃N₄ or SiO₂). The MWCNTs/SiO₂/n-Si device is used here as reference, since the SiO₂/Si system is the most widely investigated structure in microelectronics. The electrical and optical characteristics of the reference device are compared with the corresponding of our basic MWCNTs/Si₃N₄/n-Si device. The MWCNTs are deposited on the substrate with the drop casting technique. Optical performance of the SiO₂ device is comparable to the Si₃N₄ device thus revealing a quite interesting response under UV illumination. The Si₃N₄ device exhibited a peak equivalent quantum efficiency (EQE) of 57% at 3 μW of source illumination power, thus demonstrating a superior performance as compared to the SiO₂ device (EQE of up to 55%, which is also promising for future applications). This performance can be attributed to the great absorption in UV region of CNTs layer. Apart from this technological goal, we also investigated how MWCNTs/Si₃N₄ or MWCNTs/SiO₂ heterojunctions perform using standard electrical characterization techniques and how the presence of the CNTs change the dielectric characteristics of both substrates.

Silver(I) selenide, Ag₂Se was very simply and conveniently prepared from Ag and Se powders in a stoichiometric ratio by one-step mechanochemical synthesis after 10 min of milling in a planetary ball mill. The kinetics of this synthesis and the structural, morphological, optical, and thermoelectric properties of the product were studied. The crystal structure, physical properties, and morphology were characterized by X-ray diffraction (XRD), specific surface area measurements, particle size distribution analysis, scanning, and transmission electron microscopy. XRD confirmed the orthorhombic crystal structure of naumannite, Ag₂Se. The electron microscopy revealed that the nanostructured product consisted of isolated rod-shaped particles and agglomerated nanoparticles of irregular shape which formed clusters with a size >30 μm. Crystallinity was inspected by selected area diffraction. The optical properties were studied using ultraviolet-visible and photoluminescence spectroscopy. The determined band gap energy of 1.15 eV was blue-shifted relative to the bulk Ag₂Se. For the densification of mechanochemically synthesized powdered Ag₂Se, the spark plasma sintering method was applied to prepare a suitable sample for thermoelectric characterization. High-temperature thermoelectric properties were evaluated in terms of the potential application of mechanochemically synthesized Ag₂Se in energy conversion.