Scaled-up System Research Articles

Recent Trends and Prospects of Microbial Fuel Cell Technology for Energy Positive Wastewater Treatment Plants Treating Organic Waste Resources

Microbial fuel cell (MFC) technology is receiving a lot of attention recently as a promising technology for generating electricity by treating organic waste resources. Over the past 20 years, the MFC technology has made rapid progress: various research on system architectures, electrochemistry, materials, and microbiology has been conducted for developing practical ideas and fundamental principles. Recently, a lot of research on scaled-up systems for practical application is being conducted in the MFC field. In this review, materials, electrochemistry, system development and scale-up systems of MFCs studied so far are reviewed, and future prospects and directions of MFC technology are presented.

Physicochemical and Microbial Quality of Prepackaged Shrimp Processed by a Scaled-Up Microwave-Assisted Induction Heating Technology

A second generation and scaled-up equipment, named Aligo-2TM (microwave-assisted induction heating, MAIH) with a sample capacity of approximately 1.0 L was designed and invented by Bottle Top Machinery Co., Ltd., Taiwan. Pre-packaged raw shrimps were heated in a scaled-up system using heating temperatures of 130 °C and 90 °C for 80 to 150 s, and the physicochemical and microbial qualities were evaluated. The total plate count, psychrotrophic bacteria count, and coliform levels decreased as heating time increased, whereas the cooking loss, color (L*, a*, and W) value, and texture increased. When shrimps were heated for the longest time of 120 s at 130 °C or 150 s at 90 °C, they displayed obvious overcooked, shrunken, and dry appearance. To obtain samples that showed a red color, cooked well, and had no microbial count, better heating conditions for the processing of pre-packaged shrimps via the MAIH scale-up system were 130 °C for 100 s or 90 °C for 130 s. This novel and scaled-up MAIH equipment provides shrimp to be cooked after being packed, thereof avoiding the post-contamination problem.

Solar thermoelectric lab-scale system with sensible/latent heat storage for reversible power generation and warm water heating

In order to decrease greenhouse gas emissions and global warming, solar hot-water household systems containing thermoelectric generators that generate electricity and also store thermal energy are a partial potential solution. However, few studies have reported on the performance of these hybrid systems that can generate nighttime electrical power from excess stored solar thermal energy. A novel high-performance solar thermoelectric lab-scale system using composite phase change materials (consisting of paraffin, high-density polyethylene, and expanded graphite) was fabricated and tested to fill this knowledge gap. This lab-scale system's performance was evaluated by analyzing its thermal behavior both experimentally and theoretically for lab-scale use. The experimental results showed the system's maximum overall efficiency (all-day) was 55.2%. The simulated case study revealed that the scaled-up system with composite phase change materials has the potential to provide 420–426 L of warm water per day, 1.125 kWh of electricity with solar irradiance (simulating daytime operation), and 0.301 kWh of electricity at night for a standard house with 6.34 m2 of available roof surface area in Tokyo, Japan. The present study results indicated that this novel lab-scale system can utilize solar energy more effectively than conventional systems and is a promising technology to generate electricity for all-day operation and produce warm water without emitting any CO2. In other words, the proposed lab-scale system has a great potential to contribute to a future low-carbon society.

Energy Lost in a Hydrogel Osmotic Engine Due to a Pressure Drop

Utilizing hydrogels to harvest salinity gradient energy from solutions of different salinities has recently attracted interest. Polyelectrolyte hydrogels exhibit cyclic swelling/deswelling when alternately exposed to freshwater and seawater. This can be utilized to convert the mixing energy of the two solutions into mechanical energy. Hydrogels consisting of a semi-interpenetrating network (semi-IPN) of poly(4-styrene sulfonic acid-co-maleic acid) sodium salt and polyacrylic acid was prepared at various cross-linking densities. The energy lost due to a pressure drop in the system during the deswelling/swelling process of these hydrogels is examined, and the effects of tubing dimensions, hydrogel cylinder size, gel particle size, and the volume fraction within the hydrogel cylinder occupied by the flowing liquid (ε) are investigated. In addition, a small-scale osmotic engine was compared to a scaled-up system. ε was found to be the factor that had the largest effect on the energy loss. It was found that ε is strongly dependent on the degree of swelling of the hydrogels. When the hydrogels swell, they deform more easily under pressure. This markedly decreases ε, thereby inducing a high pressure drop in the system and a correspondingly large energy loss. Accordingly, the pressure drop when pumping through the hydrogel is the major contributor to the energy loss in the system. When the hydrogel particles deform too much, the energy needed to pump the flowing liquid through the hydrogels exceeds the energy produced by the system. Developing a hydrogel system that deforms less in its swollen state is therefore essential for improving the energy efficiencies of these osmotic engines.

Catalytic pyrolysis of spent coffee waste for upgrading sustainable bio-oil in a bubbling fluidized-bed reactor: Experimental and techno-economic analysis

Spent coffee waste (SCW) is extremely attractive to be exploited and utilized as a material source for energy generation and chemical production. This study concerned bio-oil production via non-catalytic and catalytic fast pyrolysis using SCW in a bubbling fluidized-bed reactor (BFR). In particular, a comparative analysis of the quality of the bio-oil produced was conducted for non-catalytic (using silica sand as the bed material) and catalytic (using dolomite, HZSM-5, hematite, and magnetite as the catalyst) fast pyrolysis. Scale-up modeling confirmed using the experimental data was performed at a feed rate of 100 kg h−1 (1,000-fold capacity), which showed different orders in the quality of energy (hematite > magnetite > dolomite > HZSM-5 > silica, in order of energy from highest to lowest) owing to the realistic integration of the BFR with other components in plants, such as the combustor, compressor, and separator. Further, techno-economic analysis of scale-up system revealed that the unit production costs of bio-oil were 0.0151, 0.0034, 0.0143, 0.0095, and 0.0102 $ MJ−1 for silica, dolomite, HZSM-5, hematite, and magnetite, respectively (dolomite > hematite > magnetite > HZSM-5 > silica, in order of unit cost from lowest to highest). Among them, dolomite and hematite showed competitive unit production costs compared to the price of conventional crude oil (0.0098 $ MJ−1). The importance of coupling laboratory-scale experimental results with scale-up modeling and economic analysis has thus been demonstrated for practical feasibility studies of the SCW pyrolysis for bio-oil production.

Liquid triphasic systems as sustainable downstream processing of Chlorella sp. biorefinery for potential biofuels and feed production

Microalgae are potential sustainable renewable sources of energy but are highly underutilized due to the expensive and time-consuming downstream processing. This study aims at curbing these obstacles by extracting multiple components with a single processing unit. In this work, an ultrasound-assisted liquid triphasic flotation system was incorporated to extract proteins, lipids, and carbohydrates by phase separation. The parameters involved were optimized and the final recovery efficiency of proteins, lipids, and carbohydrates was determined. A control run involving conventional three-phase partitioning and a 15-fold scale-up system with the recycling of phase components were also performed. Gas Chromatograph and Fourier Transform Infrared spectroscopy were used to examine the potential of extracted products as a source of biofuel. This biorefinery approach is crucial in commercializing microalgae for biodiesel and bioethanol generation with a side product of purified proteins as feed.

A cryogenic CMOS chip for generating control signals for multiple qubits

Scaled-up quantum computers will require control interfaces capable of the manipulation and readout of large numbers of qubits, which usually operate at millikelvin temperatures. Advanced complementary metal–oxide–semiconductor (CMOS) technology is an attractive platform for delivering such interfaces. However, this approach is generally discounted due to its high power dissipation, which can lead to the heating of fragile qubits. Here we report a CMOS-based platform that can provide multiple electrical signals for the control of qubits at 100 mK. We demonstrate a chip that is configured by digital input signals at room temperature and uses on-chip circuit cells that are based on switched capacitors to generate static and dynamic voltages for the parallel control of qubits. We use our CMOS chip to bias a quantum dot device and to switch the conductance of a quantum dot via voltage pulses generated on the chip. Based on measurements from six cells, we determine the average power dissipation for generating control pulses of 100 mV to be 18 nW per cell. We estimate that a scaled-up system containing a thousand cells could be cooled by a commercially available dilution refrigerator. A platform based on complementary metal–oxide–semiconductor (CMOS) technology operating with qubits close to 100 mK can generate static and dynamic signals for the control of many qubits.

Assessment and optimization of a decentralized food-waste-to-energy system with anaerobic digestion and CHP for energy utilization

Biogas derived from the decentralized anaerobic digestion (AD) of food waste may be used to generate electrical and thermal energy for nearby residents through combined heat and power generation technology. A mobile food-waste-to-energy system in conjunction with an anaerobic digester and biogas engine was developed for food waste (FW) treatment and energy output. The scale-up was simulated to explore the methane yield and energy flow at different ambient temperatures of 0 °C, 10 °C, 20 °C, 30 °C and different feedstock of 200 kg, 500 kg FW. Accordingly, the results demonstrated that the installed system with a 1 m3 digester had a methane yield of 0.55L CH4 /g VS when the feedstock load was 30 kg FW/d and the Organic Load Rate (OLR) was 5.4 g VS /L, while the thermal and electrical efficiencies of this system were 31% and 16%, respectively. The corresponding exhaust gas of the thermal energy from the biogas combustion was recovered by a heat exchanger in order to keep the digester at mesophilic conditions. The simulations carried out on the scale-up systems under loads of 200 kg FW/d and 500 kg FW/d achieved a thermal energy balance at different ambient temperatures of 0 °C, 10 °C, 20 °C and 30 °C. Improvements were proposed in the optimized system by optimizing pre-treatment facilities as well as the AD reactor, biogas engine and heat exchanger. The net thermal and electrical energy output of the optimized system at 500 kg FW/d were 175.93kWh and 163.90kWh, respectively. The energy generated by the FW-to-energy system illustrated by the Sankey diagrams depicts that was enough for operation without the need of extra heat and a power supply, moreover, the surplus energy may be utilized for its neighboring communities. In addition, the optimized system under the same OLR were increased by 87% and 135%, regards the thermal and electrical energy outputs, respectively in comparison with the current system.

An Ideal Structure for Li-Ion Battery Separators

Among all types of Li-ion battery (LIB) separators, fibrous mats have the advantage of low cost, low mass, and high porosity. Fibrous Poly(Vinylidene difluoride) (PVDF) shows promising results because of its stability and affinity for electrolytes commonly employed in Li-ion cells. Despite numerous studies published on LIB separators, none reports structure-property relationships for the identification of an ideal structure. We investigated the properties of a melt-blowable PVDF and produced meltblown PVDF mats in scale-up equipment with the objective of elucidating its performance as a LIB separator. We also present a new class of LIB separators, PVDF-based highly-branched, colloidal polymer particulates called soft dendritic colloids that are produced by shear-driven polymer precipitation within a highly turbulent nonsolvent flow, followed by filtration. We show that the morphology of the resulting PVDF particulates can be modulated from fibrous soft dendritic colloids (SDC) to thin and highly porous sheet-like particles.Through a scale-up system, we obtained high-quality meltblown PVDF with high homogeneity, low number of defects, an average fiber diameter of 1.4 μm, and pore size as low as 0.9 μm. Small fiber diameter provides high-surface area and high-electrolyte uptake. We show interactions of the meltblown PVDF with the electrolyte lead to a morphology change in the fibers. The highest ionic conductivity was ~ 9.6 mS/cm, and the first-cycle capacity was 140 mAh/g (Li/LiCoO2). After melt-pressing, the thickness and pore size decrease, but the mats electrolyte absorbency and conductivity decrease commensurately. PVDF SDC separators show high porosity (up to 80%) and high particle surface area, which results in high conductivity (1.2 mS/cm), high-electrolyte uptake (325%), and high-cell capacity (112 mAh/g in Li/LiCoO2 cell) with <10% loss after 50 cycles. Both processes yield separators with low thermal shrinkage (<5% at 90 ºC) and high tensile strength (<0.5% offset at 1000 psi), with the highest-performing separator possessing low average fiber diameter with a wide diameter distribution.Both meltblowing and shear-driven precipitation are facile and versatile processes for high-volume fabrication of LIB separators with one single polymer without necessarily requiring post-processing and with characteristics similar to commercially available battery separators. Our findings show that battery separators should be fabricated with a low pore size (<2 µm) but also with a wide pore distribution. When the strength and openness of the micropores are coupled with a dense net of nanopores, an ideal Li-ion battery separator is obtained.

Localization and Actuation for MNPs Based on Magnetic Field-Free Point: Feasibility of Movable Electromagnetic Actuations.

Targeted drug delivery (TDD) based on magnetic nanoparticles (MNPs) and external magnetic actuation is a promising drug delivery technology compared to conventional treatments usually utilized in cancer therapy. However, the implementation of a TDD system at a clinical site based on considerations for the actual size of the human body requires a simplified structure capable of both external actuation and localization. To address these requirements, we propose a novel approach to localize drug carriers containing MNPs by manipulating the field-free point (FFP) mechanism in the principal magnetic field. To this end, we devise a versatile electromagnetic actuation (EMA) system for FFP generation based on four coils affixed to a movable frame. By the Biot–Savart law, the FFP can be manipulated by appropriately controlling the gradient field strength at the target area using the EMA system. Further, weighted-norm solutions are utilized to correct the positions of FFP to improve the accuracy of FFP displacement in the region of interest (ROI). As MNPs, ferrofluid is used to experiment with 2D and 3D localizations in a blocked phantom placed in the designed ROI. The resultant root mean square error of the localizations is observed to be approximately 1.4 mm in the 2D case and 1.6 mm in the 3D case. Further, the proposed movable EMA is verified to be capable of simultaneously scanning multiple points as well as the actuation and imaging of MNPs. Based on the success of the experiments in this study, further research is intended to be conducted in scale-up system development to design precise TDD systems at clinical sites.

Impacts of Temperature and Solids Retention Time, and Possible Mechanisms of Biological Hydrolysis Pretreatment on Anaerobic Digestion

Anaerobic digestion (AD) has benefits in sludge management, energy recovery, and pathogen reduction. In order to better understand the mechanisms of biological hydrolysis (BH) pretreatment on AD, biochemical methane potential (BMP) and continuous stirred-tank reactor (CSTR) tests were utilized to compare untreated municipal combined sludge with pilot-scale BH pretreated sludge. During the BH process, there was 15%, 30%, and 33% (w/w) volatile solids (VS) reduction after BH at 42 °C (BH42) for 24, 48, and 72 h, respectively; under BH61 (42 °C for 36 h and 61 °C for 6 h), and there was 10% and 30% (w/w) overall VS reduction after 36-h and 42-h hydrolysis, respectively. BMP results showed that BH42-pretreated sludge had 22.6% enhancement of methane yield compared to untreated sludge, and BH61 pretreated sludge had 29.4% enhancement of methane yield. Both temperature and solids’ retention time (SRT) contributed to the enhanced AD performance within 36 h, while temperature played more important roles after 36-h BH pretreatment. CSTR tests confirmed the acceleration of anaerobic digestion by BH pretreatment, and higher enhancement was observed when SRT of anaerobic digestion was shorter than 16 days. Through a literature review of BH-related studies, the possible mechanisms were highlighted for further optimization on the scale-up systems in order to reduce carbon footprint and operating expenditure for wastewater treatment plants.

Catalytic Paper Filters for Diesel Soot Abatement: Studies at Laboratory and Bench Scales

A scaling-up of the impregnation process for the preparation of catalytic ceramic papers was developed by which Co and Ce oxides were incorporated on to a ceramic paper structure. To this end, a spray generator and a vacuum system were coupled, allowing the preparation of catalytic ceramic papers in the form of circular sheets 16 cm in diameter and 0.3-cm thick. The catalytic papers were set inside a metallic case in order to conform a diesel particulate filter (DPF), which was tested at bench scale placing the filter at the exhaust pipe of a FIAT turbocharged diesel engine. The catalytic ceramic papers showed elevated capacity to trap soot particles, as opacity measurements indicated. Temperature-programmed oxidation (TPO) was employed to evaluate the performance of the catalytic systems both for the simultaneous combustion of soot and hydrocarbons collected after test bench runs. TPO results for soot combustion on catalytic papers prepared at laboratory scale (1.6 cm diameter) were compared with those obtained for the scaled-up system (16 cm diameter) incorporating soot from a suspension of the carbonaceous particles in n-hexane. Similar activities were obtained, indicating the success of the scaling-up procedure. Bench-scale tests showed that catalytic ceramic papers have mechanical and catalytic properties adequate to be used as DPF.

Effect of thermosonication in a continuous system on indigenous microflora, milk quality, and consumer acceptance

Increasing pasteurized milk shelf life has been a concern for the dairy industry. This study evaluated the effect of pasteurization (control) coupled with thermosonication (treatment) (11.1 s) in a continuous system on shelf-life parameters during storage along with consumer liking. Treatment samples had significantly lower microbial counts than control during storage. Lower free fatty acid and higher pH and casein/total protein values were observed for treatment samples during storage. In a consumer panel, panelists commented on treatment samples having an unknown off-flavor. This unknown flavor declined after 4 days and the consumer liking of treatment samples after 4 days in a second consumer panel was not significantly different than control. Thermosonication in a continuous system coupled with pasteurization successfully improved the overall quality of whole milk as compared to heat only. Future studies could investigate thermosonication conditions to minimize changes in milk sensory attributes. Practical applications Thermosonication when applied with pasteurization improves the microbial quality of milk during storage and may extend the shelf life by 2 weeks. Increased shelf life could possibly lead to reduced milk loss on the consumer level by extending the time milk can be consumed. Scale-up systems will need to evaluate the effect of thermosonication at specific residence times and sonication power levels on milk quality during storage and consumer acceptance.

KINETIC AND EQUILIBRIUM STUDY ON THE ADSORPTION OF METHYLENE BLUE FROM AQUEOUS SOLUTION ONTO COFFEE HUSK ACTIVATED CARBON

In this study, the adsorption kinetics and equilibrium of methylene blue from aqueous solution onto activated carbon derived from coffee husk using one step ZnCl2 activation were investigated. The influence of initial methylene blue concentration and temperature were evaluated employing the batch experiment. To the experimental data, different kinetics and isotherm models were applied, finding that the best fitted is the pseudo-second-order equation and the Redlich-Peterson model, respectively. The mechanism of the adsorption was examined using the Weber and Morris model, and the obtained results suggested that the intra-particle diffusion was not the only rate-controlling step. The scale-up system was also designed for 50 - 90% methylene blue removal from an initial concentration of 100 mg L-1 at 30 oC.

Translation of small-scale CAR-T cell manufacturing methods to a clinical-scale production platform

Background & Aim CAR-T cells have displayed potent antitumor effects in liquid but not in solid tumors. Variables like technical and immuno-oncological factors contribute to the modest clinical effect of CAR-Ts in solid tumors. To improve their function, manufacturing conditions have been optimized to yield a favorable CAR-T cell phenotype. A product enriched in stem cell- and central memory T cells (TCM) is believed to improve durability of antitumor responses and engraftment of the adoptive cells, where highly differentiated T cell products may be prone to exhaustion and senescence. Finding optimal manufacturing conditions requires testing of media components and selection of appropriate bioreactor system for scale-up. To avoid the substantial costs of multiple bioreactor runs, screening typically relies on flask scale. We set out to determine the predictive ability of the flask-scale screening on the process performance in clinical scale. Glioblastoma-specific CAR-Ts were produced from six healthy donors in various medium compositions and compared to those produced in closed-system bioreactors. Methods, Results & Conclusion Lentivirally-transduced CAR-T cells were cultured in flasks in Miltenyi TexMACS medium with or without human AB serum (HABS) and either IL2 or IL7 and IL15. In the bioreactor process, T cells were purified and transduced in the Miltenyi CliniMACS Prodigy system, then further expanded in IL7 and IL15 containing HABS-free media in a suspension bioreactor. We characterized the cells by CAR expression level, viability, expansion rate, memory phenotype and in vitro functionality. All CAR-T products were highly viable and specifically cytotoxic, though biological differences between donors can cause variation. The main difference between culture conditions was in expansion rates. The phenotype was substantially effector memory T cell-biased in all flask cultures. The presence or absence of HABS rather than cytokine selection appeared to be the main determinant of the product characteristics. In our bioreactor scale pilot the lead media composition (IL7, IL15, no HABS) yielded a markedly different product, seen as superior expansion and significant enrichment of the TCM fraction. Our results suggest that small-scale screening may translate poorly to bioreactor systems. Such factors as medium replenishment, oxygenation, cell density and culture vessel rocking may have an impact on the product. Early-stage scale-up and testing using the final platform is essential for product success.

All-Day Energy Harvesting Power System Utilizing a Thermoelectric Generator with Water-Based Heat Storage

Solar thermal systems, especially solar hot water household heating/storage systems, are considered the most cost-effective alternatives to fossil fuel hot water heating energy systems. Recently, solar hot water systems are combined with a thermoelectric generator, forming hybrid systems. However, these hybrid systems described in the literature cannot generate electricity from sunset to sunrise, or at night, when residential consumers use the most electricity. In this paper, an all-day energy harvesting power system utilizing a thermoelectric generator with water-based heat storage is presented to generate electricity all-day and also produce warm water. The experimental and theoretical analyses were conducted to evaluate and verify the performance of the systems. In the case study, the scaled-up system shows potential to provide 198.9 L of warm water per day, 0.912 kWh of electricity in the daytime, and 0.0332 kWh of electricity at nighttime for a typical house with 6.34 m2 of available surface area in Tokyo, Japan. Although the electric power at night is low, this novel lab-scale system shows the potential to be a viable source of electricity and warm water throughout the day, without emitting any greenhouse gas.

Transforming Opacity Verification to Nonblocking Verification in Modular Systems

We consider the verification of current-state and $K$ -step opacity for systems modeled as interacting nondeterministic finite-state automata. We describe a new methodology for compositional opacity verification that employs abstraction, in the form of a notion called opaque observation equivalence, and that leverages existing compositional nonblocking verification algorithms. The compositional approach is based on a transformation of the system, where the transformed system is nonblocking if and only if the original one is current-state opaque. Furthermore, we prove that $K$ -step opacity can also be inferred if the transformed system is nonblocking. We provide experimental results where current-state opacity is verified efficiently for a large scaled-up system.

Efficient Overproduction of Active Nitrile Hydratase by Coupling Expression Induction and Enzyme Maturation via Programming a Controllable Cobalt-Responsive Gene Circuit.

A robust and portable expression system is of great importance in enzyme production, metabolic engineering, and synthetic biology, which maximizes the performance of the engineered system. In this study, a tailor-made cobalt-induced expression system (CIES) was developed for low-cost and eco-friendly nitrile hydratase (NHase) production. First, the strong promoter Pveg from Bacillus subtilis, the Ni(II)/Co(II) responsive repressor RcnR, and its operator were reorganized to construct a CIES. In this system, the expression of reporter green fluorescent protein (GFP) was specifically triggered by Co(II) over a broad range of concentration. The performance of the cobalt-induced system was evolved to version 2.0 (CIES 2.0) for adaptation to different concentrations of Co(II) through programming a homeostasis system that rebalances cobalt efflux and influx with RcnA and NiCoT, respectively. Harnessing these synthetic platforms, the induced expression of NHase was coupled with enzyme maturation by Co(II) in a synchronizable manner without requiring additional inducers, which is a unique feature relative to other induced systems for production of NHase. The yield of NHase was 111.2 ± 17.9 U/ml using CIES and 114.9 ± 1.4 U/ml using CIES 2.0, which has a producing capability equivalent to that of commonly used isopropyl thiogalactoside (IPTG)-induced systems. In a scale-up system using a 5-L fermenter, the yielded enzymatic activity reached 542.2 ± 42.8 U/ml, suggesting that the designer platform for NHase is readily applied to the industry. The design of CIES in this study not only provided a low-cost and eco-friendly platform to overproduce NHase but also proposed a promising pipeline for development of synthetic platforms for expression of metalloenzymes.

A Modular Millifluidic Platform for the Synthesis of Iron Oxide Nanoparticles with Control over Dissolved Gas and Flow Configuration.

Gas–liquid reactions are poorly explored in the context of nanomaterials synthesis, despite evidence of significant effects of dissolved gas on nanoparticle properties. This applies to the aqueous synthesis of iron oxide nanoparticles, where gaseous reactants can influence reaction rate, particle size and crystal structure. Conventional batch reactors offer poor control of gas–liquid mass transfer due to lack of control on the gas–liquid interface and are often unsafe when used at high pressure. This work describes the design of a modular flow platform for the water-based synthesis of iron oxide nanoparticles through the oxidative hydrolysis of Fe2+ salts, targeting magnetic hyperthermia applications. Four different reactor systems were designed through the assembly of two modular units, allowing control over the type of gas dissolved in the solution, as well as the flow pattern within the reactor (single-phase and liquid–liquid two-phase flow). The two modular units consisted of a coiled millireactor and a tube-in-tube gas–liquid contactor. The straightforward pressurization of the system allows control over the concentration of gas dissolved in the reactive solution and the ability to operate the reactor at a temperature above the solvent boiling point. The variables controlled in the flow system (temperature, flow pattern and dissolved gaseous reactants) allowed full conversion of the iron precursor to magnetite/maghemite nanocrystals in just 3 min, as compared to several hours normally employed in batch. The single-phase configuration of the flow platform allowed the synthesis of particles with sizes between 26.5 nm (in the presence of carbon monoxide) and 34 nm. On the other hand, the liquid–liquid two-phase flow reactor showed possible evidence of interfacial absorption, leading to particles with different morphology compared to their batch counterpart. When exposed to an alternating magnetic field, the particles produced by the four flow systems showed ILP (intrinsic loss parameter) values between 1.2 and 2.7 nHm2/kg. Scale up by a factor of 5 of one of the configurations was also demonstrated. The scaled-up system led to the synthesis of nanoparticles of equivalent quality to those produced with the small-scale reactor system. The equivalence between the two systems is supported by a simple analysis of the transport phenomena in the small and large-scale setups.

An omnidirectional WPT platform for distributed fully implanted neural recording systems

Recent progress on human brain science requires developing advanced neural recording system to capture the activity of large neural populations accurately, across a large area of the brain, and over extended periods. Recently proposed distributed neural recording systems with numerous implanted devices require reliably energizing them wirelessly. Random distribution of these mm-sized implants and brain motion place them at different positions and orientations with respect to the power transmitter. Therefore, traditional wireless power transfer techniques fall short of reaching sufficient power for all implants simultaneously, rendering some implants nonfunctional. In this paper, a three-layer power transmitting array with three-phase coil excitation current is introduced, which is capable of producing omnidirectional and homogeneous magnetic field across the volume where the Rx coils are located. The individual coil dimensions in the array is optimized to improve the worst-case scenario in terms of homogeneity, which is further verified by the measurements using a scaled-up prototype system. The measurement results show that the minimum received voltages is improved from 0.34 V for 10-mm side-length hexagonal transmitting coil array to 0.83 V for the optimal case, i.e., 35 mm side-length hexagonal transmitting coil array.