Micro and Nano Systems Letters最新文献

To investigate the effect of the surface roughness of 3D-metal-printed sub-THz components, the WR-10 3-inch-long waveguide and 24 dBi rectangular horn antenna were 3D-metal-printed using a titanium alloy powder and a high-resolution 3D metal printer. The characterized surface roughness of the printed components was 17.27 µm in RMS from a 3D optical surface profiler, and a nodule ratio of 7.89 µm and surface ratio of 1.52 for Huray model from the analyzed SEM images. The measured results of the 3D-metal-printed waveguide and rectangular horn antenna were compared with the ones of commercial waveguide and horn antenna having the same shapes. The 3D-metal-printed waveguide has 4.02 dB higher loss than the commercial waveguide, which may be caused by an ohmic loss of 0.85 dB and a surface roughness loss of 2.81 dB. The 3D-metal-printed horn antenna has 2 dB higher loss then the commercial horn antenna, which may be caused by an ohmic loss of 0.2 dB, surface roughness of 0.1 dB and fabrication tolerance loss of 1.7 dB. The loss separation was done from the EM simulation by changing the conductor material and surface roughness.

The Phlomis bracteosa Royle ex Benth. is one of the medicinal plants used by the people of the north-western Himalayan region, India. Initially, phytochemical components of this plants have been evaluated by estimating total phenolic, flavonoid and tannin contents, and also by GCMS analysis in acetone and methanol solvents, which listed twenty-four compounds in acetone and twenty-two in methanol extract with different percentage peak areas. Later, silver nanoparticles (SNPs) were biogenically synthesized from the acetone extract of the same plant. The formation of SNPs was observed with UV-vis spectroscopy with surface plasmon resonance (SPR) at 438 nm. Further, the Fourier transform infrared spectroscopy suggested the presence of carbonyls, nitrogenous compounds and different types of hydrocarbons in SNPs. The field emission scanning electron microscopy (FESEM) and the high-resolution transmission electron microscopy suggested the spherical shape of SNPs with average size of 43.53 ± 0.71 nm. On the other hand, the energy dispersive X-ray spectroscopy depicted Ag as major element, the selected area electron diffraction and the X-ray diffraction supported crystalline nature of synthesized SNPs. The antimicrobial and antioxidant activities of both extracts (acetone and methanol) and SNPs were also studied. For the antimicrobial activity analysis, disk diffusion and broth microdilution methods were selected which displayed that plant extracts (PEs) exhibited better activity against Gram-positive bacteria and were inactive against Escherichia coli, while synthesized SNPs displayed better antimicrobial activity against all selected microorganisms. In case of antioxidant activity, by following two methods i.e., DPPH radicle scavenging and reducing power methods again SNPs expressed better antioxidant property with lower IC₅₀ value (40.55 µg/mL) than PEs i.e., 93.48 µg/mL (acetone) and 92.57 µg/mL (methanol). Therefore, biosynthetic SNPs can be a useful strategy in the biomedical sector.

Metal-Assisted Chemical Etching (MACE) is a technique for precisely forming nanostructures on semiconductor substrates, and it is actively researched in various fields such as electronic devices, optoelectronic devices, energy storage, and conversion systems. This process offers economic efficiency and effectiveness because it can be performed in a simple chemical laboratory environment without the need for expensive equipment. Particularly, MACE is recognized as an excellent technology for forming various nanostructures due to its advantage of precisely controlling the shape, size, and orientation of nanostructures compared to traditional etching techniques. MACE operates by inducing electrochemical reactions using a metal catalyst, selectively etching the semiconductor surface in a mixed solution of hydrofluoric acid (HF) and hydrogen peroxide ((hbox {H}_2hbox {O}_2)). The metal catalyst reacts with the oxidant to generate holes, which are injected into the semiconductor substrate to promote oxidation reactions. The oxidized material is then dissolved by HF, progressing the etching process. Precise nanostructures are formed only in the areas with the metal catalyst, and the etching results vary depending on the type, thickness, and deposition method of the catalyst. In this study, we comprehensively review the mechanism of the MACE process, the patterns of nanostructure formation according to the characteristics of catalysts and substrates, and the influence of process variables. We also analyze application cases of MACE in various semiconductor substrates such as silicon (Si), germanium (Ge), indium phosphide (InP), and gallium arsenide (GaAs), and examine the latest research trends and applications utilizing MACE. Nanostructures formed through MACE have the potential to maximize the performance of next-generation semiconductor and optoelectronic devices, and research in this area is expected to greatly contribute to the future development of the semiconductor industry.

Brain-on-a-chip is an emerging field involving microfluidic devices capable of mimicking the structure and function of the human brain. Existing research often focuses on single barriers, such as the blood–brain barrier or blood–cerebrospinal fluid barrier (BCSFB). However, the brain has both barriers working together, and mimicking this dual system is crucial for better understanding of brain (patho)physiology. In this work, we present a four-channel microfluidic chip model that incorporates both the BBB and BCSFB, to reproduce physiologically correct architecture. Using computer simulations, we demonstrate that this model can mimic both healthy and diseased states by adjusting the shear stress experienced by the barriers, which is a key factor in their function. These findings offer valuable insights for designing future brain-on-a-chip devices with improved accuracy. This improved technology could contribute to wider advancements in tissue engineering and the study of brain function and diseases.

Organoids are three-dimensional cell clusters derived from stem cells and closely resemble the physiological characteristics of human tissues. As the next-generation biological model, organoids provide new opportunities for drug discovery, disease modeling, and personalized medicine. To fully harness the potential of organoids, real-time monitoring of biological states and functional evaluation of organoids are crucial. This review highlights recent advances in real-time, in situ biosensing technologies, including microelectrode arrays for electrophysiological recordings, chemical sensors for biochemical detection, and strain sensors for monitoring mechanical properties. While the development of miniature sensors for non-invasive, long-term, and real-time monitoring of organoids is in the early stage, these sensors are an essential part of organoid technology which would provide new insights into human developmental biology, pathophysiology, and drug discovery. After reviewing the seminal works on the microfabricated sensors for organoids, we also provide an outlook of the field including a discussion on the remaining challenges and future directions with a focus on integration of multiple sensors to facilitate organoid research and applications.

In this paper, using high-dose implantation of O₂⁺ ions, nano-sized WO₃ films were obtained on the surface and at various depths of W(111) for the first time. It has been confirmed that when O₂⁺ ions are implanted into W at room temperature with low energy, partial formation of oxides such as WO, WO₂, WO₃ and WO₄ occurs. It has been proved that in order to obtain a homogeneous and good stoichiometry of W oxide, it is necessary to carry out oxidation at a certain temperature. The optimal modes for obtaining hidden oxide layers in the near-surface region of tungsten, the substrate temperature W, the energy and dose of O₂⁺ ions were determined. The concentration profiles of distributed O atoms in depth were studied for the three-layer W-WO₃-W(111) system. Using scanning electron microscopy, the formation depths and thicknesses of WO₃ layers were determined. The WO₃ films were polycrystalline. The resulting films have potential for creating thin-film OLED displays, as well as nanofilm MOS transistors.

Digital microfluidic systems, based on the electrowetting-on-dielectric mechanism, allow the manipulation, dispensing, merging, splitting, and mixing of micro- to nanoliter droplets on hydrophobic surfaces by applying voltages to an array of planar electrodes. The manipulation of both a non-aqueous and an aqueous phase droplet in a single experiment has gained considerable interest. This study focuses on characterizing the dispensing and dosing of 1-octanol droplets, merging with a water droplet, and phase separation with minimal residue formation by shearing off the biphasic droplet at a tear-off edge of a hydrophilic well, using optimized actuation parameters. The volume of the 1-octanol droplet dispensed from an L-junction reservoir design increased with increasing dispensing speed. Dispensing can only occur within a certain reservoir volume range. Under identical conditions, 1-octanol droplets could be dispensed with volume variations of less than 0.55%, and manipulated at a maximum velocity of 5.6 mm/s when the frequency of the applied AC voltage was about 200 Hz. At the tear-off edge of the hydrophilic well, the 1-octanol residue on the water droplet was reduced to less than 0.15% of the original 1-octanol droplet volume. The results will be used for future applications, such as for the precise quantitative characterization of the reaction kinetics of complex parallel or sequential interfacial catalytic reactions, for the study of self-assembly processes or for liquid–liquid extractions at the 1-octanol–water interface.

This work evaluates the use of zinc oxide nanorods as intensifiers of a latent heat thermal energy storage system working with adipic acid as the phase change material (PCM). By virtue of not participating directly in the solid–liquid and liquid–solid phase transition, ZnO-adipic acid composites (ZnO-adipic acid) possessed lower specific heat and latent heat. Our results have shown that the overall heat transfer coefficient during the freezing of PCM through heat transfer to a well-mixed liquid bath is amplified by 61%, when adipic acid is replaced with 2 wt.% ZnO-adipic acid. Heterogenous nucleation due to well-dispersed, ZnO nanorods caused this enhancement. The large enhancement in discharge rate of 2 wt.% ZnO-adipic acid during freezing overweighs higher degree of latent heat loss due to its repeated thermal cycling. The enhancement in overall heat transfer coefficient reported here (61%) is the highest reported so far for any latent heat thermal energy system employing adipic acid or its composites.

The present study explores the application of X-ray scattering, using synchrotron radiation, to assess the diffusive transport of nanomedicines in tumor on a chip devices fabricated by 3D stereolithography using a resin with high optical and X-ray transmittance. Unlike conventional methods that require fluorescent labeling of nanoparticles, potentially altering their in vitro and in vivo behavior, this approach enables the investigation of the transport properties for unlabeled nanoparticles. In particular, the results presented confirm the influence of the porosity of the extracellular matrix-like microenvironment, specifically Matrigel, on the diffusive transport of oligonucleotide-functionalized gold nanoparticles. The analysis of the scattering patterns allows to create 2D maps showing the nanoparticle distribution with high spatial resolution. The proposed approach demonstrates the potential for studying other factors involved in nanoparticle diffusion processes. By implementing X-ray scattering to track unmodified nanomedicines within extracellular matrix-like microenvironments, increasingly accurate models for evaluating and predicting therapeutics transport behaviors can be developed.

Simultaneous detection of multiple neurotransmitters and their related activities is crucial for enhancing our understanding of complex neurological mechanisms and disorders. In this study, we developed a flexible, high-sensitivity multi-electrodes array probe capable of concurrent detection of four neurotransmitters: dopamine, serotonin, acetylcholine and glutamate. The probe was fabricated on a polyimide substrate with 16 circular gold-film electrodes. These electrodes were modified with PEDOT/GluOx and PEDOT/ChOx for enzymatic detection of glutamate and acetylcholine, and with rGO/PEDOT/Nafion for the detection of dopamine and serotonin. Our electrochemical sensor achieved sensitivities of 184.21 and 219.29 μA/μM cm² for glutamate and acetylcholine, respectively, with limits of detection (LOD) of 0.0242 and 0.0351 μM within a concentration range of 0.1–100 μM. For dopamine and serotonin, the sensor showed sensitivities of 195.9 and 181.2 μA/μM cm², respectively, with LOD of 0.4743 and 0.3568 μM. This research advances the field of neurochemical sensing and provides valuable insights into the balance of neurotransmitters associated with neurological disorders. These insights improve diagnostic and therapeutic strategies.