Small Devices Research Articles

Organic Solar Modules with Good Stability under Ultraviolet Irradiation

One of the most crucial considerations for practical applications of organic photovoltaics (OPV) is the stability under sunlight irradiation. It is necessary to translate the small device stability to the module level. Herein, the photostability of the OPV module with three cells connected in series with a total effective area of 10.8 cm2 is presented. The stability of the OPV module is studied under continuous irradiation by a UV light‐emitting diode (LED) with integrated UV intensity the same as AM1.5 solar irradiations. As a result, the OPV module achieves good stability under UV light with a half‐lifetime of about 1300 h without a UV filter. The lifetime is similar to the small device with the same materials. The series resistance and the encapsulation must be optimized simultaneously. The suitable metal of the external electrode greatly improves the OPV module's performance. In addition, the UV stability of the normal structure is shown to be better than the inverted structure because of the photoinstability of the ZnO layer. Moreover, the UV stability of semitransparent OPV modules is shown to be‐ similar to the opaque ones.

Boosting the triboelectric performances of biowaste chitosan keratin triboelectric nanogenerator using carbon composite film as charge storage and charge recombination blocking intermediate layer

Environmental conservation efforts are promoting energy-generation technologies that avoid the use of highly polluting fuels and promote the reuse of waste materials. Advances in triboelectric nanogenerators (TENGs) have led to the progress in harvesting energy from ambient mechanical sources and powering small devices and sensors while being compact, flexible, biocompatible, and eco-friendly. Nevertheless, the practical applications of TENG have limitations. Therefore, the development of TENG with excellent triboelectric performance, eco-friendliness, and low cost is crucial. Consequently, an environmentally friendly, inexpensive TENG device with outstanding triboelectric performance was designed using keratin-enhanced chitosan as a tribo-positive material, a carbon film as an intermediate layer, and polytetrafluoroethylene as a triboelectric negative material. The device was purposely designed to simultaneously play a role in waste treatment and efficient green energy harvesting. Therefore, keratin was extracted from recycled fur, and a carbon film was selected to enhance the triboelectric performance because of its excellent electrical conductivity and dielectric constant. The triboelectric properties of a chitosan keratin intermediate layer (CKI)-TENG were systematically investigated. Practical applications of the CKI-TENG in charging electronic devices and waste-noise harvesting were also studied. The developed CKI TENG exhibited outstanding triboelectric performance compared to a TENG device without an intermediate layer. Particularly, the charge transfer, output voltage, and power density was improved by 19%, 46%, and 60%, respectively, compared to the output of the chitosan-keratin (CK) TENG device. It also exhibited outstanding cyclic and charging-discharging stabilities. In addition, the power density of the developed CKI TENG was higher than that of previously reported TENG devices. Thus, it can play a significant role in green and clean energy generation and the utilization of the harvested energy in practical applications, such as biomedical sensors, charging electronic devices, smart textiles, and sensors.

Meta Heuristic Technique with Reinforcement Learning for Node Deployment in Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are vital in applications like environmental monitoring, smart homes, and battlefield surveillance. Comprising small devices with limited resources, WSNs require efficient node deployment for power optimization and prolonged network lifetime, ensuring sufficient coverage and connectivity. This study introduces an Intelligent Satin Bower Bird Optimizer augmented with reinforcement learning (ISBO-RL), enhancing coverage and connectivity. ISBO-RL focuses on optimal sensor placement for improved coverage and connectivity, using an Optimum Position Finding (OPF) method to identify key sensor node locations. Reinforcement learning is integrated into the ISBO algorithm, allowing nodes to adapt based on performance and changing conditions. Experimental results on diverse platforms highlight ISBO-RL’s efficacy and its superior coverage and connectivity performance as compared to other algorithms. ISBO-RL represents a significant advancement in the field of Wireless Sensor Networks, offering a promising solution to address the challenges of efficient node deployment and network optimization in various critical applications.

Size-dependent electrochemistry of laser-induced graphene electrodes

Laser-induced graphene (LIG) electrodes have become popular for electrochemical sensor fabrication due to their simplicity for batch production without the use of reagents. The high surface area and favorable electrocatalytic properties also enable the design of small electrochemical devices while retaining the desired electrochemical performance. In this work, we systematically investigated the effect of LIG working electrode size, from 0.8 mm to 4.0 mm diameter, on their electrochemical properties, since it has been widely assumed that the electrochemistry of LIG electrodes is independent of size above the microelectrode size regime. The background and faradaic current from cyclic voltammetry (CV) of an outer-sphere redox probe [Ru(NH3)6]3+ showed that smaller LIG electrodes had a higher electrode roughness factor and electroactive surface ratio than those of the larger electrodes. Moreover, CV of the surface-sensitive redox probes [Fe(CN)6]3– and dopamine revealed that smaller electrodes exhibited better electrocatalytic properties, with enhanced electron transfer kinetics. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy showed that the physical and chemical surface structure were different at the electrode center versus the edges, so the electrochemical properties of the smaller electrodes were improved by having rougher surface, more density of the graphitic edge planes, and more oxide-containing groups. The difference could be explained by the different photothermal reaction time from the laser scribing process that causes different stable carbon morphology to form on the polymer surface. Our results give a new insight on relationships between surface structure and electrochemistry of LIG electrodes and are useful for designing miniaturized electrochemical devices.

Student Attendance using RFID System

An RFID-based attendance system leverages radio frequency identification technology to streamline and automate the process of tracking attendance in various settings, such as schools, workplaces, and events. This system utilizes RFID tags, which are small electronic devices containing unique identification codes, embedded in cards or badges assigned to individuals. When a person with an RFID-enabled badge enters a designated area, RFID readers detect their presence by wirelessly communicating with the tags. This information is then transmitted to a central database or software system, where attendance records are automatically updated in real-time. Compared to traditional methods like manual entry or barcode scanning, RFID-based systems offer greater efficiency, accuracy, and convenience, reducing administrative burden and eliminating possibilities of human error. Additionally, they provide valuable data insights for monitoring attendance patterns, enhancing security, and optimizing resource allocation.

Correlating Aggregation Ability of Polymer Donors with Film Formation Kinetics for Organic Solar Cells with Improved Efficiency and Processability.

Film formation kinetics significantly impact molecular processability and power conversion efficiency (PCE) of organic solar cells. Here, two ternary random copolymerization polymers are reported, D18─N-p and D18─N-m, to modulate the aggregation ability of D18 by introducing trifluoromethyl-substituted pyridine unit at para- and meta-positions, respectively. The introduction of pyridine unit significantly reduces material aggregation ability and adjusts the interactions with acceptor L8-BO, thereby leading to largely changed film formation kinetics with earlier phase separation and longer film formation times, which enlarge fiber sizes in blend films and improve carrier generation and transport. As a result, D18─N-p with moderate aggregation ability delivers a high PCE of 18.82% with L8-BO, which is further improved to 19.45% via interface engineering. Despite the slightly inferior small area device performances, D18─N-m shows improved solubility, which inspires to adjust the ratio of meta-trifluoromethyl pyridine carefully and obtain a polymer donor D18─N-m-10 with good solubility in nonhalogenated solvent o-xylene. High PCEs of 13.07% and 12.43% in 1 cm2 device and 43 cm2 module fabricated with slot-die coating method are achieved based on D18─N-m-10:L8-BO blends. This work emphasizes film formation kinetics optimization in device fabrication via aggregation ability modulation of polymer donors for efficient devices.

In-situ welding and thermal activation enabled robust nanofibers based triboelectric nanogenerator for sustainable energy harvesting

Nanofiber-based triboelectric nanogenerators (TENGs) show great promise in energy harvesting and sensing applications. However, the poor strength and the instability of the nanofiber structures lead to the constraints on the durability and the lack of stability in the output performance. In this study, BaTiO3@PVDF-HFP nanofibers were prepared by electrospinning, in which BaTiO3 nanoparticles enhanced the charge trapping ability of the nanofibers and provided nucleation sites for β-phase growth. Subsequent solvent and annealing treatment in-situ welded the nanofibers, which greatly improved the mechanical strength and stability of the nanofiber membranes. The annealing process further thermally activated the electroactive β-phase in the PVDF-HFP, which increased the surface charge density of the nanofibers. A flexible TENG based on BaTiO3@PVDF-HFP-p nanofiber was prepared to harvest mechanical energy, which could achieve a maximum output of 482.5 V and 1.9 W m−2, the voltage is more than 1.2–1.5 times higher compared to uncrosslinked nanofibers. The BaTiO3@PVDF-HFP-p-based TENG maintains ultra-stable Voc generation over 7000 cycles compared to the nanofibers without solvent and annealing treated. Finally, its practical application in harvesting ambient mechanical energy was demonstrated, which can harvest wind energy to power LEDs and small electronic devices such as temperature and humidity sensors.

A high performance triboelectric nanogenerator using assembled sugar naphthalimides for self-powered electronics and sensors

A new class of N-glycosyl naphthalimide ricinoleate (NGNR) amphiphiles were generated using environmentally friendly reaction conditions in good yields. To investigate the potential applications of NGNR amphiphiles within the realm of supramolecular materials, molecular self-assembly experiments were conducted extensively across a diverse range of solvents and oils and observed the gel formation. Molecular-level interactions and assembly patterns were investigated by employing FTIR, SAXRD, UV–vis, and fluorescence spectroscopy, and a plausible assembly mechanism was proposed. The morphology of the supramolecular architecture was identified by scanning electron microscopy. Additionally, rheological studies provided insight into these soft materials' strength and processability. Further, in the process of fabricating a triboelectric nanogenerator (TENG) device, silicone rubber serves as an electron acceptor and assembled NGNR serves as an electron donor. The developed TENG demonstrated a significant improvement in performance over TENG made with amorphous NGNR, with output voltage, current, and power density of 410 V, 100 µA, and 5.1 W/m2, respectively, highlighting the importance of the assembly process. Furthermore, TENG is used to continuously power up small electronic device (calculator), which is useful in building self-powered electronic devices. Lastly, due to its high sensitivity and stability, the TENG was used to detect the humidity of the environment in the food processing, textile, and agriculture sectors. The change in TENG response is notably significant up to 70 % relative humidity (RH). This work showcases the development of self-powered humidity sensors.

Multi-scale boiling heat transfer investigation on micro-thin aluminum heaters

Nucleate boiling is a highly efficient heat transfer mode distinguished by the liquid-vapor phase change, which occurs through the formation, growth, and detachment of vapor bubbles from a heated surface. Its crucial role in various industrial applications, such as nuclear power plant operation and effective heat management in small electronic devices, has driven significant research efforts. However, despite extensive research dedicated to boiling investigations, there are still substantial knowledge gaps that hinder our ability to accurately predict heat removal rates. These knowledge gaps arise from the complex nature of small-scale boiling phenomena, which are further complicated by their strong dependence on operating conditions and the interactions between walls and fluids. In an effort to address some of these gaps, we conducted multi-scale investigations during pool boiling of de-ionized water on micro-thin aluminum heaters. We captured bubble dynamics through multiple synchronized diagnostic sources, including high-speed backlit imaging to track bubble growth, synchronized high-speed infrared thermometry to capture the corresponding thermal footprint on the boiling surface, and in-house developed fast-response micro-thermocouples to measure temperature at multiple locations within the fluid. Our study reveals peculiar aspects of heat transfer mechanisms occurring at single bubble level (low heat fluxes) and in fully developed nucleate boiling regimes (high heat fluxes).

Compact cryogenic hydrogen test environment for small devices and material characterization

Currently, there is a great need for testing capabilities for material samples and components in LH2. This includes low temperature compatibility at 20 K, H2 compatibility and potential degradation or permeation effects. The test environment required for this is challenging and quite costly due to LH2 supply. Therefore, an alternative test concept was developed whereby the required amount of LH2 (typically 2–3 L) is generated directly on-site by simple condensation. This is achieved with a power-controlled cryocooler (115 W @ 80 K, 18 W @ 20 K). A cylindrical pressure vessel with an inner diameter of d = 109 mm and a length of approx. 500 mm designed for 2.1 MPa is used to hold the LH2 bath and the samples. The cryocooler and the sample chamber are installed in a common vacuum cryostat and are thermally coupled at the lower end. At the 20 K level, thermal coupling is achieved by a sophisticated thermosiphon arrangement. Hydrogen is taken from a pressure reservoir, pre-cooled at the cryocooler 80 K level, and then injected and liquefied within a couple of hours.

Contribution to the world of 3D cell products created by bio 3D printing technology and to the life science field

We have been making 3D tissues consist of cells only, based on the corporate philosophy of "contributing to dramatic advances in medical care through the practical application of innovative 3D cell stacking technology." Currently, in the field of regenerative medicine, we are working toward obtaining approval from the Ministry of Health, Labor and Welfare and commercializing large artificial organs that are made from patients' own cells and have functions such as nerve regeneration, osteochondral regeneration, and blood vessels. On the other hand, this three-dimensional cell stacking technology can be extended to technology for culturing cells in an environment similar to the human body, and is expected to serve as a new methodology for evaluating the effects of new products in various fields on living organisms. Therefore, we are planning a business to provide developers of pharmaceuticals, foods, cosmetics, etc. with a small device called "Functional Cell Device (FCD)" that reproduces some of the functions of human organs outside the body. As the first step, we have developed a three-dimensional liver construct (3D mini-liver). The in vitro human liver model has a wide range of usage, such as evaluation of hepatotoxicity of drugs, elucidation of drug metabolism mechanism, and model of liver disease. In this report, we will outline it together with actual examples in regenerative medicine.

Multi-component 20La2O3–20TiO2–20Nb2O5-20(Al2O3/ZrO2)-20(ZrO2/Ta2O5) glasses with ultra-high refractive index and mechanical properties inspired by high-entropy design

The highly refractive glasses with excellent mechanical properties (hardness, Young's modulus, and fracture toughness) are highly desired for the lenses used in small optical devices. In this study, a series of five-primary-component 20La2O3–20TiO2–20Nb2O5-20(Al2O3/ZrO2)-20(ZrO2/Ta2O5) (LTNAZ, LTNAT, LTNZT) glasses were designed by using high-entropy strategy and successfully elaborated through a containerless melting-solidification process. The highest refractive index (nd) of the glasses reach up to 2.25. The maximum vickers hardness (HV), Young's modulus (E), and indentation fracture toughness (KIFT) are 10.74 GPa, 157.5 GPa, and 1.23 MPa m0.5 respectively. The glasses exhibit good glass forming ability with kinetic window (ΔT) ranging from 80 to 116 °C. The excellent comprehensive performances of the glasses are attributed to the high electronic polarizability and dissociation energy, as well as the synergistic effect of multiple components in the high-entropy effect. The glasses will be promising host materials for optical applications such as digital product lenses, endoscopes and mini size lasers.

Pengaruh Penggunaan Gagdet terhadap Hasil Belajar Siswa Kelas XII MIPA SMAN 5 Model Palu pada Mata Pelajaran Biologi

Gadgets are small electronic devices that have special functions to download the latest information. The use of gadgets is not only limited to the entertainment aspect, but has also penetrated into the world of education, especially among students. This study aims to describe the effect of gadget use on the learning outcomes of students of class XII MIPA SMAN 5 Model Palu in Biology subject. This type of research is descriptive quantitative. The sample in this study were XII MIPA class students of SMAN 5 Model Palu as many as 55 students using purposive sampling technique. Data collection techniques using questionnaires and documentation. Data analysis techniques were performed with normality test, simple linear regression test and F test. The results showed that there is a positive influence of gadget use on student learning outcomes at SMAN 5 Model Palu. Through hypothesis testing with the F test, the f-table is obtained at 4.02 so that f-count = 28.238> f-table = 4.02 which means it has a significant effect.

Miniaturized gas exposure devices for atom probe experiments.

To detect hydrogen in materials at the atomic scale, atom probe tomography is now regularly used. In order to avoid cumbersome cryo-preparation to suppress diffusion, often hydrogen is charged only into the finished specimen. Here, the use of hydrogen gas over electrochemical hydrogen has the advantage that the specimen is not contaminated with an electrolyte. So far, this "charging" has been done in large, expensive systems. Here, we introduce small devices that enable the exposure of atom probe specimens to hydrogen and potentially other gases, using only very small gas volumes. This enables the operation in regular laboratory environments without additional safety measures. These devices can be used to expose the specimen to hydrogen up to 10 bar/90°C. Higher temperatures may be attained with small changes. Validation of the success of charging with these setups is demonstrated through experiments employing deuterium charging of palladium atom probe tips. RESEARCH HIGHLIGHTS: Enabling the exposure of atom probe specimens to hydrogen and potentially other gases, using only very small gas volumes. Built setups can be assembled with little money and from freely available parts, making specimen charging much easier. Validation of the success of charging with these setups is demonstrated through experiments employing deuterium charging of palladium atom probe tips.

Rectenna System Development Using Harmonic Balance and S-Parameters for an RF Energy Harvester.

With the escalating demand for Radio Frequency Identification (RFID) technology and the Internet of Things (IoT), there is a growing need for sustainable and autonomous power solutions to energize low-powered devices. Consequently, there is a critical imperative to mitigate dependency on batteries during passive operation. This paper proposes the conceptual framework of rectenna architecture-based radio frequency energy harvesters' performance, specifically optimized for low-power device applications. The proposed prototype utilizes the surroundings' Wi-Fi signals within the 2.4 GHz frequency band. The design integrates a seven-stage Cockroft-Walton rectifier featuring a Schottky diode HSMS286C and MA4E2054B1-1146T, a low-pass filter, and a fractal antenna. Preliminary simulations conducted using Advanced Design System (ADS) reveal that a voltage of 3.53 V can be harvested by employing a 1.57 mm thickness Rogers 5880 printed circuit board (PCB) substrate with an MA4E2054B1-1146T rectifier prototype, given a minimum power input of -10 dBm (0.1 mW). Integrating the fabricated rectifier and fractal antenna successfully yields a 1.5 V DC output from Wi-Fi signals, demonstrable by illuminating a red LED. These findings underscore the viability of deploying a fractal antenna-based radio frequency (RF) harvester for empowering small electronic devices.

IMPROVING THE ENGINEERING PROPERTIES OF CLAYEY SOIL USING SILICA FUME AND SISAL FIBER

Building on soft soils continues to be a challenge for civil engineers in the modern world, despite the rapid development of infrastructure projects and advancements in construction technology. They exhibit a large volumetric change upon contact with water, which is the cause of their limited bearing capacity. Various stabilization strategies can be used to handle the soft clay's shear strength issue. In this experiment, sisal fibers and silica fumes were added in different amounts to the clay soil in order to determine the ideal moisture content and strength parameters for reaching the maximum dry density of the soil. By adjusting the amount of sisal fiber for each amount of silica fume, the Unconfined Compressive Strength (UCS) test has been used to examine the strength of both natural clay and clay modified with silica fume (6%, 12%, 18%) and sisal fibers (0.5%, 1.0%, 1.5%) separately, as well as the combination of all the materials. Using a small compaction device, standard proctor test was used to determine the ideal moisture content and maximum dry density. According to the test results, the maximum dry density falls with increasing silica fume content likewise, the maximum dry density increases with increasing sisal fiber content. The addition of 12% silica fume and 2.0% sisal fiber to the clay sample results in a maximum strength when taking the strength parameter into account. Key Words: Compaction test, CBR, UCS, Silica fume, Sisal Fiber

A Reduced Order Series Expansion for the BEM Incorporating the Boundary Layer Impedance Condition

When modeling sound waves in fluids it can be important to include the viscous and thermal losses originating from the fluids’ interaction with boundaries. In the audible frequency range, the thickness of the boundary layers is between a micrometer and a millimeter. As such the viscous and thermal losses are important when simulating the properties of small acoustical devices such as e.g. hearing aids or transducers. However, the inclusion of viscous and thermal losses is a computationally demanding task as it requires a fine discretization of the boundary layer in order to fully capture the complicated physical phenomena happening on the microscale. Recently, there has been developments to ease the computational demands using both the Finite Element Method and the Boundary Element Method, by approximating the losses using the Boundary Layer Impedance (BLI) boundary condition. In this paper, we extend previous developments for multi-frequency analysis using the Reduced Order Series Expansion Boundary Element Method to handle the BLI condition. This model follows a two-step procedure: Using a series expansion to decrease the assembly time of the BEM matrices and a projection to reduce the overall memory consumption of the model. Results from two acoustic interior problems show that the model decreases the total computational time by around 96% while using less than 15% of the memory. For both test setups the limiting factor of the accuracy was the reduction and not the series expansion.

Incorporating MIL‐125 Metal‐Organic Framework for Flexible Triboelectric Nanogenerators and Self‐Powered Sensors for Robotic Grippers

AbstractTriboelectric nanogenerators (TENGs) are getting popular as biomechanical energy harvesters to power small electronic devices and as self‐powered sensors for pressure, motion, vibration, wind, waves, biomedical information, and chemical substance detections. In this study, the TENG is designed with biocompatible materials, and concentrations of its components have been optimized to generate higher power for application as an energy source and tactile sensor. The process involves using metal‐organic frameworks (MOFs), namely MIL‐125, with high charge‐inducing and charge‐trapping capabilities incorporated into the commercial Ecoflex matrix. Electrical characterization demonstrated that the sample with 0.25 wt% MIL‐125 (0.25%MOF/Ecoflex) is the optimal concentration in the matrix with an output of up to 305 V and 13 µA, respectively. Moreover, the proposed flexible TENG converts mechanical energy to electrical, with a maximum power density of 150 µW cm−2 (1.5 W m−2), which is more than twice superior to the pristine Ecoflex‐based counterparts. The TENG shows robust and stable performance without noticeable degradation during continuous 200,000 cyclic testing. Furthermore, 0.25%MOF/Ecoflex TENG can power small electronic devices such as calculators, humidity sensors, and cardiac pacemakers. A robotic gripper trained via machine learning to identify various objects is also successfully developed with a self‐powered 0.25%MOF/Ecoflex TENG sensor.

Flexible polydimethylsiloxane pressure sensor with micro-pyramid structures and embedded silver nanowires: A novel application in urinary flow measurement

Flexible pressure sensors are lightweight and highly sensitive, making them suitable for use in small portable devices to achieve precise measurements of tiny forces. This article introduces a low-cost and easy-fabrication strategy for piezoresistive flexible pressure sensors. By embedding silver nanowires into a polydimethylsiloxane layer with micro-pyramids on its surface, a flexible pressure sensor is created that can detect low pressure (17.3 Pa) with fast response (<20 ms) and high sensitivity (69.6 mA kPa−1). Furthermore, the pressure sensor exhibits a sensitive and stable response to a small amount of water flowing on its surface. On this basis, the flexible pressure sensor is innovatively combined with a micro-rotor to fabricate a novel urinary flow-rate meter (uroflowmeter), and results from a simulated human urination experiment show that the uroflowmeter accurately captured all the essential shape characteristics that were present in the pump-simulated urination curves. Looking ahead, this research provides a new reference for using flexible pressure sensors in urinary flow-rate monitoring.

3D-Continuous Nanoporous Covalent Framework Membrane Nanoreactors with Quantitatively Loaded Ultrafine Pd Nanocatalysts.

The confinement effect of catalytic nanoreactors containing metal catalysts within nanometer-sized volumes has attracted significant attention for their potential to enhance reaction rate and selectivity. Nevertheless, unregulated catalyst loading, aggregation, leaching, and limited reusability remain obstacles to achieving an efficient nanoreactor. A robust and durable catalytic membrane nanoreactor prepared by incorporating palladium nanocatalysts within a 3D-continuous nanoporous covalent framework membrane is presented. The reduction of palladium precursor occurs on the pore surface within 3D nanochannels, producing ultrafine palladium nanoparticles (Pd NPs) with their number density adjustable by varying metal precursor concentrations. The precise catalyst loading enables controlling the catalytic activity of the reactor while preventing excess metal usage. The facile preparation of Pd NP-loaded free-standing membrane materials allows hydrodechlorination in both batch and continuous flow modes. In batch mode, the catalytic activity is proportional to the loaded Pd amount and membrane area, while the membrane retains its activity upon repeated use. In continuous mode, the conversion remains above 95% for over 100h, with the reactant solution passing through a single 50µm-thick Pd-loaded membrane. The efficient nanoporous film-type catalytic nanoreactor may find applications in catalytic reactions for small chemical devices as well as in conventional chemistry and processes.