Micro and Nano Systems Letters最新文献

Silicon-on-insulator (SOI) wafers offer significant advantages for both Integrated circuits (ICs) and microelectromechanical systems (MEMS) devices with their buried oxide layer improving electrical isolation and etch stop function. For past a few decades, various approaches have been investigated to make SOI wafers and they tend to exhibit strength and weakness. In this review, we aim to overview different manufacturing routes for SOI wafers with specific focus on advantages and inherent challenges. Then, we look into how SOI wafers are characterized for quality assessment and control. We also provide insights towards potential future directions of SOI technology to further accelerate ever-growing IC and MEMS industries.

The main goal of this research is to compare the rheological behavior of hybrid nano lubricants (HNLs) with different composition ratios in a base oil. The purpose of the comparison is to determine the HNL with the best lubrication performance at the start of the vehicle. Theoretical methods have confirmed the non-Newtonian behavior in different laboratory conditions. HNLs with the composition ratio of 30:70 and 25:75 had the highest percentage of increase and decrease in viscosity, respectively 34.97% and − 1.85% at T = 55 °C, shear rate SR = 6665 s⁻¹ and solid volume fraction SVF = 1% and T = 5 °C, SR = 3999 s⁻¹ and SVF = 0.05%. To predict the viscosity of the desired HNL, in the RSM, a special model with an accuracy of R² = 0.9997 has been used. The margin of deviation (MOD) is determined in the range of − 3.43% < MOD < 4.75%. Viscosity sensitivity analysis shows that the greatest sensitivity will result from SVF changes at high SVFs. The experimental results of this study will introduce the optimal nano polishing to the craftsmen, and the theoretical part of this study will save the researchers from spending time and excessive economic costs.

Capacitive pressure sensors are essential for advanced applications like wearable medical devices, electronic skins, and biological signal detection systems. Enhancing sensitivity in these sensors is achieved by incorporating porous microstructures into the dielectric layer. The present research focuses on designing a capacitive pressure sensor comprising a porous micro-pyramidal dielectric layer featuring diagonally arranged pyramids. The effects of geometric parameters and material properties such as dielectric constant, porosity, base length, tip width, height, and the distance between the pyramidal microstructures were examined using the three-dimensional finite element simulations. A comparative analysis was conducted to evaluate the accuracy of the numerical solution. The simulation results were compared to experimental measurements, and the findings revealed a high level of agreement. The optimal quantity of data for this analysis was determined using the design of the experiment method, specifically the response surface model. The results show that arranging microstructures diagonally or laterally can impact sensitivity and initial capacitance. Specifically, employing a diagonal arrangement enhanced sensor sensitivity by up to 1.65 times while maintaining the initial capacitance relatively unaffected. Ultimately, this study derived mathematical equations from the collected data to estimate the initial capacitance and sensitivity of the sensor. The model predictions were compared to simulation results, and it was found that the models performed effectively.

Nanofluids for enhanced oil recovery offer a breakthrough solution towards tertiary recovery and consequently higher oil production. Their ability to reduce interfacial tension, alteration of formation’s wettability, higher adsorption capacity, and acceleration of disjoining pressure makes them excellent candidates for enhanced oil recovery. The main objective of this paper is to investigate the effect of polymers on zinc oxide (ZnO) nanofluids for enhanced oil recovery (EOR) and the role played by chemical modification using polymer stabilizers on nanoparticle stability in nanofluids. Nanoparticles with an average particle size of 34 nm were synthesized and used to prepare nanofluids of different concentrations and their stability was evaluated using sedimentation and UV–vis spectrophotometry tests. ZnO-synthesized nanofluids were used solely and in addition to Polyvinylpyrrolidone (PVP) and Polyvinyl alcohol (PVA) as stabilizing agents. It was noted that ZnO nanofluids with PVA stabilizer recorded the highest oil recovery of 82%. In contrast, the ZnO nanofluids without stabilizing agents registered the lowest recovery rate during the flooding experiment. The results revealed that a higher injection rate increases the oil recovery and reduces the viscous fingering effect with a better displacement front. Furthermore, nanofluids containing polymeric stabilizing agents achieved better recovery factors compared to ZnO nanofluids without stabilizing agents. This phenomenon was also observed in the interfacial tension test where nanofluids with PVA and PVP stabilizers reduced the IFT by 59% and 61% respectively.

Deterministic lateral displacement (DLD) is a passive, label-free, continuous-flow method for particle separation. Since its discovery in 2004, it has been widely used in medical tests to separate blood cells, bacteria, extracellular vesicles, DNA, and more. Despite the very simple idea of the DLD method, many details of its mechanism are not yet fully understood and studied. Known analytical equations for the critical diameter of separated particles include only the gap between the columns in the DLD array and the fraction of the column shift. The dependence of the critical diameter on the post diameter, channel height, and a number of other geometric parameters remains unexplored. The problems also include the effect of flow rate and particle concentration on the critical diameter and separation efficiency. At present, DLD devices are mainly developed through numerical simulation and experimental validation. However, it is necessary to find fundamental regularities that would help to improve the separation quantitatively and qualitatively. This review discusses the principle of particle separation, the physical aspects of flow formation, and hydrodynamic forces acting on particles in DLD microchannels. Various analytical models of a viscous flow in an array of cylindrical posts are described. Prospects for further research are outlined.

Microelectronic retinal implants can restore a useful level of artificial vision in photoreceptor-damaged retina. Previously commercialized retinal prostheses require transocular connection lines to an external power supply and/or for data transmission, which are unwieldy and may cause unwanted side effects, such as infections. A recently reported wireless device used a rigid silicon substrate. However, it had the potential for a long-term mechanical mismatch with soft retinal tissue. In this work, we used organic photovoltaic materials which can be fabricated on flexible substrates as well as be operated without any physical connection to the external world. The present study employed PCE10 as an active layer for retinal prosthetic application for the first time. Compared to previously studied organic photovoltaic materials used in retinal prosthesis research (such as P3HT), our PCE10 devices showed higher efficiency, providing a huge advantage in this field. When the PCE10 was blended with other non-fullerene acceptors achieving a ternary organic photovoltaic layer (PCE10:ITIC:Y6 blend), it showed lower reduction of photocurrent under same irradiation frequency condition. The fabrication method for our organic photovoltaic device was simple and easy to control its thickness. The fabricated devices showed adequate photocurrent to stimulate the retinal neurons with a smaller reduction in generated photocurrent during repeating stimuli compared to P3HT or PCE10 alone.Author names: Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Author: Given name [Jae Young] Last name [Kim]. Author: Given name [Byung Chul] Last name [Lee].Yes, they are correct.

Laser-induced graphene (LIG) has attracted significant interest in the field of pressure sensors owing to the high sensitivity associated with its inherent three-dimensional porous structure. However, the brittleness of fabricated LIG poses a critical challenge in terms of durability. To address this issue, current research on LIG-based pressure sensors has focused on the utilization of Si-elastomer encapsulation layers. Despite the importance of the mechanical properties of Si elastomers for the performance of physical sensors, few studies have been conducted on the characterization of pressure sensors based on the encapsulation layer. In this study, we investigated the electromechanical characteristics of LIG-based pressure sensors encapsulated in various Si-based elastomers. For an unbiased evaluation, we first introduce a simple and reliable fabrication process for LIG-based pressure sensors with different Si-elastomer encapsulation layers. Subsequently, the electromechanical responses of the sensors were characterized using an automated pressure machine, demonstrating that sensors with encapsulation layers with a lower Young’s modulus exhibited increased resistance changes and extended response times. Finally, an in-depth exploration of the environmental stability of the pressure sensors was conducted for various encapsulation materials, ultimately confirming negligible performance variations based on the encapsulation materials.

Two-photon lithography has emerged as a highly effective method for fabricating intricate three-dimensional (3D) microstructures. It enables the rapid fabrication of 3D microstructures, unlike conventional two-dimensional nanopatterning. Researchers have extensively investigated two-photon polymerization (TPP) for the fabrication of diverse 3D micro/nanodevices with high resolution. TPP can be applied in cell cultures, metamaterials, optical materials, electrical devices, and fluidic devices, to name a few. In this study, we investigate the applications and innovative research pertaining to TPP, which is an effective fabrication technique with significant advancement in various fields. In particular, we attempt to determine the reasons that cause the detachment or delamination of 3D microstructures during the development process and propose some solutions. A step-by-step fabrication process for a glass substrate, from photoresist deposition to laser scanning and the dissolution of the uncured photoresist, is presented. Defects such as pattern delamination are discussed, with emphasis on the cell scaffold structure and microlens array. Understanding and addressing these defects are vital to the success of 3D microstructure fabrication via TPP.

Human-machine interface has been considered as a prominent technology for numerous smart applications due to their direct communication between humans and machines. In particular, wearable electronic skins with a free form factor have received a lot of attention due to their excellent adherence to rough and wrinkled surfaces such as human skin and internal organs. However, most of the e-skins reported to date have some disadvantages in terms of mechanical instability and accumulation of by-products at the interface between the human skin and the device. Here, we report a mechanically stable e-skin via a newly designed pattern named the “eyes.” The ingeniously designed pattern of the eyes allowed mechanical stress and strain to be dissipated more effectively than other previously reported patterns. E-skin permeability of by-product was experimentally confirmed through sweat removal tests, showing superior sweat permeability compared to conventional e-skins. Finally, the real-time monitoring of the body temperature was carried out using our resistive-type thermometer in the e-skin.

This paper presents the development of a flexible temperature sensor array using multi-layer ceramic capacitors. By integrating the capacitors into a 5 × 5 array on a polydimethylsiloxane (PDMS) substrate, we exploit the principle of changing dielectric constant with temperature, which results in a change in capacitance. Our sensor array demonstrates a consistent decrease in capacitance with increasing temperature, with a sensitivity ranging from 1.42 to 1.62 pF/°C. This sensitivity range is maintained even when measurements are taken using a capacitance-to-voltage conversion circuit, with a sensitivity of 1.1 to 1.5 mV/°C. The repeatability and hysteresis of the sensors were also investigated, with the latter revealing a maximum error of 12.7%. Our findings provide valuable insights for the development of efficient, flexible, and reliable temperature sensor arrays using ceramic capacitors.