Highly-sensitive wafer-scale transfer-free graphene MEMS condenser microphones

Since the performance of micro-electro-mechanical system (MEMS)-based microphones is approaching fundamental physical, design, and material limits, it has become challenging to improve them. Several works have demonstrated graphene's suitability as a microphone diaphragm. The potential for achieving smaller, more sensitive, and scalable on-chip MEMS microphones is yet to be determined. To address large graphene sizes, graphene-polymer heterostructures have been proposed, but they compromise performance due to added polymer mass and stiffness. This work demonstrates the first wafer-scale integrated MEMS condenser microphones with diameters of 2R = 220-320 μm, thickness of 7 nm multi-layer graphene, that is suspended over a back-plate with a residual gap of 5 μm. The microphones are manufactured with MEMS compatible wafer-scale technologies without any transfer steps or polymer layers that are more prone to contaminate and wrinkle the graphene. Different designs, all electrically integrated are fabricated and characterized allowing us to study the effects of the introduction of a back-plate for capacitive read-out. The devices show high mechanical compliances Cm = 0.081-1.07 μmPa-1 (10-100 × higher than the silicon reported in the state-of-the-art diaphragms) and pull-in voltages in the range of 2-9.5 V. In addition, to validate the proof of concept, we have electrically characterized the graphene microphone when subjected to sound actuation. An estimated sensitivity of S1kHz = 24.3-321 mV Pa-1 for a Vbias = 1.5 V was determined, which is 1.9-25.5 × higher than of state-of-the-art microphone devices while having a ~9 × smaller area.

Agricultural machinery automatic navigation technology

In this paper, we review, compare, and analyze previous studies on agricultural machinery automatic navigation and path planning technologies. First, the paper introduces the fundamental components of agricultural machinery autonomous driving, including automatic navigation, path planning, control systems, and communication modules. Generally, the methods for automatic navigation technology can be divided into three categories: Global Navigation Satellite System (GNSS), Machine Vision, and Laser Radar. The structures, advantages, and disadvantages of different methods and the technical difficulties of current research are summarized and compared. At present, the more successful way is to use GNSS combined with machine vision to provide guarantee for agricultural machinery to avoid obstacles and generate the optimal path. Then the path planning methods are described, including four path planning algorithms based on graph search, sampling, optimization, and learning. This paper proposes 22 available algorithms according to different application scenarios and summarizes the challenges and difficulties that have not been completely solved in the current research. Finally, some suggestions on the difficulties arising in these studies are proposed for further research.

Nano-clay montmorillonite removes tetracycline in water: Factors and adsorption mechanism in aquatic environments

In response to escalating environmental concerns surrounding antibiotic pollution, the utilization of calcium-montmorillonite minerals for tetracycline wastewater treatment is gaining prominence. This study systematically analyzed the physicochemical properties of calcium-montmorillonite through scanning electron microscope, contact angle analysis, X-ray diffraction, and Fourier transform infrared spectroscopy. It explored the adsorption efficacy and mechanisms for tetracycline removal, considering factors like initial pH, adsorption duration, concentration, and co-cations (Na+ and Ca2+). Under optimized conditions, achieving over 90% tetracycline removal with a maximum adsorption capacity of 526 mg/g, the study revealed competitive adsorption sites for coexisting cations. The Langmuir model best described the monolayer adsorption process, while kinetic studies favored the pseudo-first-order model. This research offers comprehensive insights into tetracycline adsorption on calcium-montmorillonite, emphasizing its potential as an efficient, cost-effective adsorbent for pharmaceutical wastewater treatment.

Synthesizing nuclear power plant fouling with fractal characteristics enables an in-depth study of concerned nuclear safety issues

Fouling deposit on nuclear fuel cladding causes wick boiling and boron hideout, resulting in localized corrosion and power shift with great potential security and economic risks. Herein, a cost-effective time-saving adjustable reproduction method combining sol-gel with ceramic sintering is presented to enable wide coverage of fouling's morphologies and microstructures. Based on fractal analysis, structurally self-similar fouling deposits from different reactors conform to proposed porosity-fractal dimension law under 3% relative error. Wick boiling and boron hideout numerical simulation based on fractal dimension is implemented to treat different morphologies and structures in a unified way. Cladding surface underneath fouling deposit has a maximum 9.243 K temperature increasement due to thermal resistance, and H3BO3 is concentrated 11.274 times by mean of wick boiling, causing Li2B4O7 precipitation under extreme conditions with low porosity and high heat flux. The insights in this study provide a precise approach for quantitative evaluation of localized corrosion and power shift.

A modular microfluidic platform to study how fluid shear stress alters estrogen receptor phenotype in ER+ breast cancer cells

Metastatic breast cancer leads to poor prognoses and worse outcomes in patients due to its invasive behavior and poor response to therapy. It is still unclear what biophysical and biochemical factors drive this more aggressive phenotype in metastatic cancer; however recent studies have suggested that exposure to fluid shear stress in the vasculature could cause this. In this study a modular microfluidic platform capable of mimicking the magnitude of fluid shear stress (FSS) found in human vasculature was designed and fabricated. This device provides a platform to evaluate the effects of FSS on MCF-7 cell line, an estrogen receptor positive (ER+) breast cancer cell line, during circulation in the vessels. Elucidation of the effects of FSS on MCF-7 cells was carried out utilizing two approaches: single cell analysis and bulk analysis. For single cell analysis, cells were trapped in a microarray after exiting the serpentine channel and followed by immunostaining on the device (on-chip). Bulk analysis was performed after cells were collected in a microtube at the outlet of the microfluidic serpentine channel for western blotting (off-chip). It was found that cells exposed to an FSS magnitude of 10 dyn/cm2 with a residence time of 60 s enhanced expression of the proliferation marker Ki67 in the MCF-7 cell line at a single cell level. To understand possible mechanisms for enhanced Ki67 expression, on-chip and off-chip analyses were performed for pro-growth and survival pathways ERK, AKT, and JAK/STAT. Results demonstrated that after shearing the cells phosphorylation of p-AKT, p-mTOR, and p-STAT3 were observed. However, there was no change in p-ERK1/2. AKT is a mediator of ER rapid signaling, analysis of phosphorylated ERα was carried out and no significant differences between sheared and non-sheared populations were observed. Taken together these results demonstrate that FSS can increase phosphorylation of proteins associated with a more aggressive phenotype in circulating cancer cells. These findings provide additional information that may help inform why cancer cells located at metastatic sites are usually more aggressive than primary breast cancer cells.

Quantifying the impact of wildfire smoke on solar photovoltaic generation in Australia

The 2019-20 Australian wildfires caused extreme haze events across New South Wales (NSW), which reduced photovoltaic (PV) power output. We analyze 30-min energy data from 160 geographically separated residential PV systems in NSW with a total capacity of 312 kW from 6 Nov 2019-15 Jan 2020. The observed mean power reduction rate for PV energy generation as a function of the fine particulate matter (PM2.5) concentration is 13 ± 2% per 100 μg/m3 of PM2.5. The resulting energy loss for residential and utility PV systems is estimated at 175 ± 35 GWh, equating to a worst-case financial loss of 19 ± 4 million USD. We found the relative impact to be most significant in the mornings and evenings, which may necessitate the installation of additional energy storage. As PV systems are sensitive to smoke and become ubiquitous, we propose employing them to support wildfire detection and monitoring.

Batteries or hydrogen or both for grid electricity storage upon full electrification of 145 countries with wind-water-solar?

Grids require electricity storage. Two emerging storage technologies are battery storage (BS) and green hydrogen storage (GHS) (hydrogen produced and compressed with clean-renewable electricity, stored, then returned to electricity with a fuel cell). An important question is whether GHS alone decreases system cost versus BS alone or BS + GHS. Here, energy costs are modeled in 145 countries grouped into 24 regions. Existing conventional hydropower (CH) storage is used along with new BS and/or GHS. A method is developed to treat CH for both baseload and peaking power. In four regions, only CH is needed. In five, CH + BS is the lowest cost. Otherwise, CH + BS + GHS is the lowest cost. CH + GHS is never the lowest cost. A metric helps estimate whether combining GHS with BS reduces cost. In most regions, merging (versus separating) grid and non-grid hydrogen infrastructure reduces cost. In sum, worldwide grid stability may be possible with CH + BS or CH + BS + GHS. Results are subject to uncertainties.

Climate change induced water stress and future semiconductor supply chain risk

Climate change is a driver of water stress risk globally. Semiconductor manufacturing requires large volumes of water. Existing research at the intersection of water stress risk and semiconductor manufacturing offers snapshots of current conditions but has not investigated how future climate scenarios may impact semiconductor supply chain security. This study combines location data for semiconductor manufacturing facilities with data on specific customer-supplier networks and with data for global water stress risk under three climate scenarios for the years 2030 and 2040. Results suggest that 40 percent of existing facilities, 24-40 percent of facilities under construction, and 40-49 percent of facilities announced since early 2021 are in basins of high- or extremely high water stress risks in 2030 and 2040. Network dynamics mean that water stress risks could cascade from individual firms or regions of concern to systemically throughout the network, thus negatively impacting semiconductor supply chain security globally.

High contrast ratio optimized total internal reflection prism for compact medium-wave IR target simulation system

The existing infrared target simulation system with a total internal reflection (TIR) prism has the problem of low imaging contrast ratio, which will seriously affect the quality of the simulated image. This study proposes a design method of optimized TIR prism (OTIR) based on Snell's law in medium-wave infrared (MWIR) to solve the problem. The radiation theory is used to construct the constraint model of the OTIR prism in the MWIR target simulation system. Further, this study investigates the influence of different states of the digital micromirror device on the beam direction and derives the design equation of the OTIR prism composed of three prisms based on Snell's law. Finally, the designed OTIR prism is simulated and experimentally verified. The simulated results show that the OTIR prism of the compact MWIR target simulation system can enhance the contrast ratio. The experimental results show that the output contrast ratio of the simulation system at 700 K is about 298:1. In the specified temperature range, the contrast ratio of the infrared target simulation system increases with the increase of the light source temperature. Thus, the OTIR prism has the function of improving the contrast ratio of MWIR target simulation system.

High-yield and rapid isolation of extracellular vesicles by flocculation via orbital acoustic trapping: FLOAT

Extracellular vesicles (EVs) have been identified as promising biomarkers for the noninvasive diagnosis of various diseases. However, challenges in separating EVs from soluble proteins have resulted in variable EV recovery rates and low purities. Here, we report a high-yield ( > 90%) and rapid ( < 10 min) EV isolation method called FLocculation via Orbital Acoustic Trapping (FLOAT). The FLOAT approach utilizes an acoustofluidic droplet centrifuge to rotate and controllably heat liquid droplets. By adding a thermoresponsive polymer flocculant, nanoparticles as small as 20 nm can be rapidly and selectively concentrated at the center of the droplet. We demonstrate the ability of FLOAT to separate urinary EVs from the highly abundant Tamm-Horsfall protein, addressing a significant obstacle in the development of EV-based liquid biopsies. Due to its high-yield nature, FLOAT reduces biofluid starting volume requirements by a factor of 100 (from 20 mL to 200 µL), demonstrating its promising potential in point-of-care diagnostics.