Micro and Nano Systems Letters最新文献

This study is focusing on the durability of fluoropolymer hydrophobic coatings against falling droplets. Devices such as smart self-cleaning lens or droplet-based energy generators are open-air electrowetting-on-dielectric (EWOD) devices, which are applications that utilize falling droplets. Therefore, the hydrophobic coatings of these devices are exposed to environment factors such as raindrop, and it is necessary to examine the durability of hydrophobic coatings in similar environments and the effectiveness of recovery. Thus, in this study, we simulate raindrops to damage samples with various thicknesses of Cytop (CTX-809SP2). Subsequently, damaged samples are heated to recover their hydrophobicity, and we repeat this damage-recovery cycle several times to evaluate the long-term durability of hydrophobic coating. The EWOD samples of three different hydrophobic coating thicknesses (0.1 μm, 0.5 μm, and 1.0 μm) are damaged by falling droplets from a certain height for 10 days. The damaged samples are then recovered by heating them on a hot plate at 200 ℃ for 24 h and evaluate their EWOD performance. In addition, the hydrophobic coatings are repeatedly damaged and recovered several times to examine the number of recovery limitations of the coatings. After the second damage-recovery cycle, the thickest hydrophobic coating sample shows 7 % better EWOD performance than others. Additionally, after the third damage-recovery cycle, the EWOD performance of all samples significantly degrade, experimentally verifying the number of recovery limitations of the hydrophobic coating. The results of this study are expected to provide useful information for open-air EWOD devices on the methods for evaluating their durability and the thickness selection of hydrophobic coating.

The World Health Organization reports that metabolic disorders are responsible for a significant proportion of global mortality. Considering this, breath sensors have gained prominence as effective tools for monitoring and diagnosing metabolic disorders, thanks to recent advancements in science and technology. In human exhaled breath, over 870 distinct volatile organic components (VOCs) have been identified. Among several VOCs, the detection of acetone in exhaled breath has received considerable attention in biomedical applications. Research indicates a strong correlation between high acetone levels in human breath and several diseases, such as asthma, halitosis, lung cancer, and diabetes mellitus. For instance, acetone is particularly noteworthy as a biomarker in diabetes, where its concentration in exhaled breath often surpasses 1.76 parts per million (ppm), compared to less than 0.8 ppm in healthy individuals. Early diagnosis and intervention in diseases associated with elevated acetone levels, aided by such non-invasive techniques, have the potential to markedly reduce both mortality and the financial burden of healthcare. Over time, various nanostructured gas sensing technologies have been developed for detecting acetone in both ambient air and exhaled breath. This article presents a mini review of cutting-edge research on acetone gas sensing, focusing specifically on nanostructured metal oxides. It discusses critical factors influencing the performance of acetone gas sensors, including acetone concentration levels and operational temperature, which affect their sensitivity, selectivity, and response times. The aim of this review is to encourage further advancements in the development of high-performance acetone gas sensors utilizing nanostructured materials, contributing to more effective management of metabolic disorders.

The utilization of high-resolution printed flexible electronic devices is prevalent in various fields, including energy storage, intelligent healthcare monitoring, soft robotics, and intelligent human–machine interaction, owing to its compact nature and mechanical flexibility. The EHD jet printing technology has the potential to develop the field of printing industry through its ability to fabricate high-resolution, flexible, stretchable, and 3D structures for electronic applications such as displays, sensors, and transistors. The EHD jet printing technology involves the use of solution-based inks made of diverse functional materials to print a wide range of structures. Consequently, it is imperative to have a comprehensive understanding of nanomaterial composites that are printed using EHD jet printing technology. This review provides a thorough overview of nanomaterial composite inks printed for electronic devices using EHD jet printing technology. In particular, a comprehensive overview has been provided about the utilization of EHD jet printing for nanomaterial composites in several domains, including flexible electrodes, flexible displays, transistors, energy harvesting, sensors, and biomedical applications. Moreover, this analysis presents a concise overview of the limitations and prospective future directions for nanomaterial composites fabricated by EHD jet printing.

This paper presents a digital microfluidic (DMF) platform based on a printed circuit board (PCB) for droplet mixing. Mixing droplets without a top cover plate is important for bio-chemical analysis. For this reason, a more efficient mixing method is required especially for mixing a viscous liquid droplet in an open surface. Here, to improve the performance of droplet mixing, we propose the integration of an acoustically oscillating bubble to an electrowetting-on-dielectric (EWOD) chip, which can generate microstreaming inside the droplet. Firstly, an EWOD chip integrated with through-holes for bubble trapping was designed and fabricated through PCB fabrication. This PCB manufacturing technology helps to place more electrodes in the limited chip size. Secondly, we developed the custom-made circuit and interface to individually control multiple actuators (including EWOD actuation and acoustic excitation). Finally, an operation test was conducted to evaluate the capability of not only droplet transportation but also mixing on an open surface. The proposed PCB-based DMF platform for bubble-induced droplet mixing was experimentally verified and expected to make DMF chips more efficient when used for clinical point-of-care diagnostic applications.

Research is being conducted on photocatalyst-based organic compound treatment processes for water purification to decompose wastewater efficiently. An optofluidic reactor based on TiO₂ photocatalysis and nanoelectrokinetics was presented recently to improve the efficacy of photocatalytic water purification. However, inefficient absorption of visible light by TiO₂ materials hinders the effective utilization of solar energy. To address this issue, the uniform formation and characterization of Au/TiO₂ nanoparticles for a plasmonic photocatalytic-based optofluidic platform are studied to improve photocatalytic reactivity in visible light. The present study uses UV irradiation and spray spraying for producing Au/TiO₂ NPs uniformly on microporous carbon fabric. Energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to assess the quality of the Au/TiO₂ NP-coated carbon fabric. Au NPs were uniformly obtained on the surface and inside the TiO₂ coating layer by UV irradiation-based photo-reduction, according to SEM and TEM investigation. The interaction of Au NPs, TiO₂ NPs, and carbon fabric (CF) to improve electron transport and charge separation on the photocatalyst surface is supported by XPS spectra. TEM and XRD analyses revealed that all TiO₂ components in the Au/TiO₂ coating layer consisted of anatase having high photocatalytic activity. After comparing the photocatalytic activity of TiO₂ and Au/TiO₂-coated samples under solar-simulated light and a voltage of 3 V, it was found that the surface coated with Au NPs had a superior photocatalytic effect than the surface coated with only TiO₂.

An asymmetric a-side alkyl chain anthracene derivative 6-(4 (-2 Ethyl Octyl) Phenyl) 2Phenyl Anthracene (EOPPA) was designed based on a π-electron skeleton with a side alkyl chain of anthracene core molecule. EOPPA was found to be a sturdy and high-performance p-type semiconductor for optoelectronic applications. The creation has successfully made this new material EOPPA with the best solubility, which exhibits both sufficient solvent solubility and thermal stability. The asymmetrical structural features of EOPPA allowed for the preparation of two-dimensional crystalline thin films in micrometer sizes with 100 nm thicknesses on a Si/SiO₂ substrate through a solution processing method. The efficient solution processing synthesis of EOPPA and its high performance suggest that it has great potential in the field of organic electronics. The EOPPA demonstrated optoelectronic properties, crystalline structure, and good thin-film transistors having mobilities higher than 0.18 cm² V⁻¹ S⁻¹, and a high current on/off ratio that can withstand temperatures of almost 225 °C. Furthermore, EOPPA presents good potential to be amongst the next generation of p-type anthracene core organic semiconductors, especially for practical printed electronics applications.

Metallic aerogels have attracted tremendous interest because of their superior properties, such as low density, high electrical conductivity, and large specific surface area. However, extremely brittle connections in their 3D networks remain a challenge. In this study, compressible aerogels with microporous fiber-like structure consisting of freeze-dried cellulose nanofibers (CNFs) and silver nanowires (AgNWs) were fabricated by unidirectional freeze-casting process. To improve the robustness, elasticity, and deformability of the aerogel, freeze-dried microfiber-structured CNFs assembled with AgNWs were used. The freeze-dried CNF/AgNW-based aerogels exhibited a low density (8.51–13.5 mg/cm³) and high porosity (up to 98.2%). Furthermore, these aerogels demonstrated impressive mechanical properties with high compressive strength (up to 4.85 kPa at 70% strain), elastic modulus (up to 16.3 kPa), and yield strength (up to 2 kPa). Additionally, the aerogels exhibited reversible deformability up to a 10% strain and maintained their durability over 200 cycles of compressive strain at 10%. The fabricated aerogels also showed a low electrical resistivity (< 8.65 mΩ·m) in addition to robust and compressible mechanical properties. These aerogels are expected to be useful in a wide range of applications that require characteristics such as light weight, high compressive strength, high elasticity, and low electrical resistivity.

In the case of a visually impaired person, literal communication often relies on braille, a system predominantly dependent on vision and touch. This study entailed the development of a visual and tactile perception technique for braille character recognition. In the visual perception approach, a braille character recognition was performed using a deep learning model (Faster R-CNN–FPN–ResNet-50), based on custom-made braille dataset collected through data augmentation and preprocessing. The attained performance was indicated by an mAP50 of 94.8 and mAP75 of 70.4 on the generated dataset. In the tactile perception approach, a braille character recognition was performed using a flexible capacitive pressure sensor array. The sensor size and density were designed according to braille standards, and a single sensor with a size of 1.5 mm × 1.5 mm was manufactured into a 5 × 5 sensor array by using a printing technique. Additionally, the sensitivity was improved by incorporating a pressure-sensitive micro dome-structured array layer. Finally, braille character recognition was visualized in the form of a video-based heatmap. These results will potentially be a cornerstone in developing assistive technology for the visually impaired through the fusion of visual-tactile sensing technology.

This paper presents a system integration of a sense-based user interface (SUI) platform, comprised of flexible pressure and humidity sensor arrays with a commercial inertial measurement unit (IMU), to analyze behavioral patterns of young children. The pressure sensors utilize a sensor array created using flexible inkjet printing, with each sensor using a piezoresistive sensing layer. The humidity sensors employ an interdigitated capacitive sensor based on a polyimide humidity-sensitive layer and are also manufactured using the flexible inkjet printing technique. To achieve a wide measurement area, both the pressure and humidity sensors are expanded into 5 × 5 and 5 × 10 sensor arrays, respectively. Also, commercial IMU, including accelerometer/gyroscope sensors, is employed. Finally, the SUI platform is in the form of a cuboidal block model, with an IMU and circuits embedded within the block. Multilayered pressure and humidity sensor arrays are installed on the external surface of the block. Collected data from each sensor are visualized through heatmaps and 3D motion representation to create a platform that integrates fine-grained behavior as well as global behavior information of young children. This research would provide a foundation for the development of SUI technology, especially aimed at individuals who have difficulty with conventional forms of input–output devices.

We have synthesized carbon nanoparticles using mandarin juice via green synthesis rout. We have doped carbon nanoparticles in liquid crystal media and studied the surface effect on self-assembly of carbon nanoclusters on ITO coated glass surface and on graphene sheet. The purpose of this study is to construct uniform nano-micro droplets for novel applications and to understand and explore the underlying science behind molecular scale reorganization in the presence of functional surfaces like graphene. We have used density functional theory approach to confirm that the carbon nanoparticles in globular structures are dispersed in presence of graphene sheet due to chemical interaction of carbon rings (or say carbon nanoparticles) with graphene carbon atoms. In order to minimize the free energy, the carbon nanoparticles leave the carbon globular structures and are dispersed to form rectangular structures in presence of LC media at graphene surface. The carbon nanoparticles are dispersed to increase contact area with graphene surface. The results are useful in construction of desired nano-micro structures for possible novel purposes in medical field since carbon nanoparticles are biocompatible. Optical microscopy, FESEM, NMR and UV spectra verifies the droplet formation and its effect on the surface and electronic properties of carbon nanoparticles.