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1.
Rev Sci Instrum ; 93(8): 083502, 2022 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-36050075

RESUMO

This work describes a novel optical heterodyne detection scheme that significantly extends the frequency response of the phase contrast imaging method to detect electron density fluctuations in tens of megahertz frequency range. The system employs a variable frequency electro-optic modulator to allow operation at any frequency in the range 10-40 MHz without the need to realign the system. The frequency coverage of the system makes it suitable to measure the radial structure of the electron density component of ion cyclotron emission on devices having confining magnetic field of a few tesla, thus extending the purely temporal measurements provided so far by magnetic probes.


Assuntos
Ciclotrons , Diagnóstico por Imagem , Magnetismo
2.
Sensors (Basel) ; 22(17)2022 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-36080842

RESUMO

The aim of this article is mathematical modelling and investigation of chosen parameters of a small energy harvesting system designed for energy harvesting from car tire mechanical vibrations to provide power supply for various sensors, e.g., in tire pressure monitoring system. The energy harvester consists of three permanent magnets inserted into a tube made from polyamide material. Comsol program has been used to calculate the force between the magnets, the stiffness of the magnetic spring, and the natural frequency of the system. MATLAB program has been used to simulate the movement of the moveable magnet to compare it with the measurements. Finally, the parameters of the mathematical model of the energy harvester were investigated and validated on a specially prepared laboratory test bench.


Assuntos
Magnetismo , Imãs , Fontes de Energia Elétrica , Movimento , Vibração
3.
Sensors (Basel) ; 22(17)2022 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-36081147

RESUMO

Magnetic particle spectroscopy (MPS) in the Brownian relaxation regime, also termed magnetic spectroscopy of Brownian motion (MSB), can detect and quantitate very low, sub-nanomolar concentrations of molecular biomarkers. MPS/MSB uses the harmonics of the magnetization induced by a small, low-frequency oscillating magnetic field to provide quantitative information about the magnetic nanoparticles' (mNPs') microenvironment. A key application uses antibody-coated mNPs to produce biomarker-mediated aggregation that can be detected using MPS/MSB. However, relaxation changes can also be caused by viscosity changes. To address this challenge, we propose a metric that can distinguish between aggregation and viscosity. Viscosity changes scale the MPS/MSB harmonic ratios with a constant multiplier across all applied field frequencies. The change in viscosity is exactly equal to the multiplier with generality, avoiding the need to understand the signal explicitly. This simple scaling relationship is violated when particles aggregate. Instead, a separate multiplier must be used for each frequency. The standard deviation of the multipliers over frequency defines a metric isolating viscosity (zero standard deviation) from aggregation (non-zero standard deviation). It increases monotonically with biomarker concentration. We modeled aggregation and simulated the MPS/MSB signal changes resulting from aggregation and viscosity changes. MPS/MSB signal changes were also measured experimentally using 100 nm iron-oxide mNPs in solutions with different viscosities (modulated by glycerol concentration) and with different levels of aggregation (modulated by concanavalin A linker concentrations). Experimental and simulation results confirmed that viscosity changes produced small changes in the standard deviation and aggregation produced larger values of standard deviation. This work overcomes a key barrier to using MPS/MSB to detect biomarkers in vivo with variable tissue viscosity.


Assuntos
Magnetismo , Nanopartículas , Biomarcadores , Nanopartículas/química , Análise Espectral , Viscosidade
4.
Phys Rev Lett ; 129(10): 103201, 2022 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-36112446

RESUMO

Enantiodetection of chiral molecules is important to chemical reaction control and biological function designs. Traditional optical methods of enantiodetection rely on the weak magnetic-dipole or electric-quadrupole interactions, and in turn suffer from the weak signal and low sensitivity. We propose a new optical enantiodetection method to determine the enantiomeric excess via two-dimensional (2D) spectroscopy of the chiral mixture driven by three electromagnetic fields. The quantities of left- and right-handed chiral molecules are reflected by the intensities of different peaks on the 2D spectrum, separated by the chirality-dependent frequency shifts resulting from the relative strong electric-dipole interactions between the chiral molecules and the driving fields. Thus, the enantiomeric excess can be determined via the intensity ratio of the peaks for the two enantiomers.


Assuntos
Eletricidade , Campos Eletromagnéticos , Magnetismo , Análise Espectral , Estereoisomerismo
5.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 4402-4406, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086020

RESUMO

A recently developed prototype (Laparoscopic Differential Magnetometer, in short LapDiffMag) identifies magnetic tracer accumulated inside sentinel lymph nodes (SLNs) during clinical laparoscopic procedures. The LapDiffMag relies on excitation of superparamagnetic iron oxide nanoparticles (SPIONs) and subsequent laparoscopic detection based on a nonlinear detection principle. The prototype uses an excitation coil to generate a magnetic field needed to activate SPIONs. This study reports on the process of developing a new excitation coil by describing the design choices based upon clinical requirements, by modeling delivered magnetic field using digital twin, and by comparing the magnetic fields of modeled and manufactured prototype. Digital twin technology was used to produce relevant and reliable data to demonstrate the safety and effectiveness of the excitation coil. The magnetic field originating from manufactured prototype was validated at two different heights above the excitation coil and have shown a good concordance to the data generated by its digital twin. Clinical Relevance- Current standard-of-care for a variety of tumor types consists of minimally invasive radical resection of primary tumor and regional lymph nodes (LNs). The newly introduced excitation coil will (after full validation) enable minimally invasive harvesting of sentinel LNs by means of magnetic tracer detection.


Assuntos
Neoplasias , Linfonodo Sentinela , Humanos , Linfonodos/patologia , Magnetismo , Neoplasias/patologia , Linfonodo Sentinela/patologia , Linfonodo Sentinela/cirurgia , Biópsia de Linfonodo Sentinela/métodos
6.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 2294-2297, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086211

RESUMO

To evaluate the hemocompatibility of individual components of our pediatric left ventricular assist device (LVAD), we proposed a hemocompatibility assessment platform (HAP) with a magnetic levitated bearing system. The HAP consists of a drive system utilizing a brushless direct current (BLDC) motor, passive magnetic bearings (PMB), and an active magnetically levitated bearing (AMB) to reduce the hemolysis generated by HAP itself. In this study, we designed and evaluated the performance of the AMB by measuring radial and axial displacements of the rotor resulting from radially destabilizing forces as well as the performance of the drive system when rotated at increasing speeds to 1,200 rotations per minute (rpm). The results show that, with radial disturbance, the AMB is capable of maintaining axial stability for the BLDC motor system. The AMB can control up to 1,200 rpm without any contact between the rotor and stator. Future work includes geometry optimization for the AMB structure and increase the capability to control stable high-speed rotation for the entire system. Clinical Relevance- This work furthers the development of the magnetic levitated bearing system for a hemocompatibility assessment platform that will be used to enhance and accelerate the development of adult and pediatric LVADs.


Assuntos
Coração Auxiliar , Magnetismo , Criança , Eletricidade , Desenho de Equipamento , Coração Auxiliar/efeitos adversos , Hemólise , Humanos
7.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 584-587, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086536

RESUMO

Magnetic induction tomography (MIT) is harmless and contactless technique for measuring the conductivity of the biological tissue. MIT could be used for initial diagnosis and continuous monitoring of stroke. Different kinds of coil arrays have been proposed for MIT systems. Previous research results using a circular 16-channel MIT model reported difficulties with detection and measurement of small bioelectric signals. For stroke imaging, a system with a higher sensitivity is required. We aim to improve the sensitivity by increasing the number of coils and placing them closer to the head. In this paper, a helmet type coil array with 31 coils is introduced. For simplicity, the head is modelled as a sphere with white matter as a material. The stroke is simulated as a single inclusion with blood and assigned different sizes and positions. Sensitivity distribution and target response of the stroke were evaluated for the helmet model and compared with the circular MIT system. The simulations and analysis were performed at 10 MHz frequency with different coil pairs. Results from comparison of the two MIT models show that the Helmet coil array provides better spatial sensitivity, which has been estimated to be more than 20 times higher than the circular model. Further, when all coils are taken in account, the recorded sensitivity improvement was in the range of 13-90-fold.


Assuntos
Dispositivos de Proteção da Cabeça , Acidente Vascular Cerebral , Condutividade Elétrica , Humanos , Magnetismo , Acidente Vascular Cerebral/diagnóstico por imagem , Tomografia/métodos
8.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 2282-2285, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086595

RESUMO

Development of pediatric left ventricular assist devices (LVADs) has lagged behind that of adult LVADs, primarily due to the size and hemocompatibility constraints of pediatric anatomy. To quantify sources of blood trauma during LVAD development, we proposed a hemocompatibility assessment platform (HAP) that can evaluate the hemocompatibility of individual components of LVADs. To eliminate the hemolysis induced by the HAP itself, we incorporated passive magnetic (PM) bearings to suspend the rotor radially and an active magnetic bearing (AMB) to control the axial position. In this study, we numerically evaluated AMB forces of 2 geometries and validated the model by comparing its predictions with experimental results. The magnetic forces generated by the AMB were evaluated by increasing the rotor-stator gap from 0.1 mm to 0.5 mm with a 0.1 mm increment and by varying the coil current from -2 A to 2 A with a 1 A increment. The average error of the numerical models was 8.8% and 7.0% for the two geometries, respectively. Higher errors were found at smaller (<0.2mm) rotor-stator gaps. For both biasing ring sizes, the AMB exhibits high magnetic stiffness from -1 A to 1 A, though it saturates for currents of -2 A and 2 A. This region of high current stiffness was identified as the optimal control region. In future work, this function will be used to tune a control algorithm to modulate current supplied to the AMB, ultimately stabilizing the rotor axially. Clinical Relevance- This work furthers the development of a hemocompatibility assessment platform that will enhance and accelerate the development of adult and pediatric LVADs.


Assuntos
Coração Auxiliar , Magnetismo , Criança , Desenho de Equipamento , Coração Auxiliar/efeitos adversos , Hemólise , Humanos , Fenômenos Magnéticos
9.
Annu Int Conf IEEE Eng Med Biol Soc ; 2022: 873-876, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-36086667

RESUMO

This work investigates the feasibility of having a mattress based wireless power transfer system with transfer efficiency such that the received power could potentially be enough to fully power up wearable systems intended to provide some level of continuous physiological monitoring; hence eliminating the need for users to ever have to recharge the systems. The novel architecture proposed in this work, to optimise power transfer efficiency against angular misalignment typical of non-static use is based on a non-coupling coil structure combined with a magnetic beamforming scheme. The coil system also incorporates a non-coupling relay array to overcome the significant loss in power transfer efficiency associated to increasing distances between transmitters and receivers. The system is proven to be able to deliver around 11.8mW of power in the worst-case scenario, with a receiver 25cm above the transmitters, whilst meeting the safety requirements associated to electromagnetic exposure to the human body.


Assuntos
Leitos , Tecnologia sem Fio , Fenômenos Eletromagnéticos , Humanos , Magnetismo , Monitorização Fisiológica
10.
Molecules ; 27(16)2022 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-36014435

RESUMO

Traditional open surgery complications are typically due to trauma caused by accessing the procedural site rather than the procedure itself. Minimally invasive surgery allows for fewer complications as microdevices operate through small incisions or natural orifices. However, current minimally invasive tools typically have restricted maneuverability, accessibility, and positional control of microdevices. Thermomagnetic-responsive microgrippers are microscopic multi-fingered devices that respond to temperature changes due to the presence of thermal-responsive polymers. Polymeric devices, made of poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAM-AAc) and polypropylene fumarate (PPF), self-fold due to swelling and contracting of the hydrogel layer. In comparison, soft metallic devices feature a pre-stressed metal bilayer and polymer hinges that soften with increased temperature. Both types of microdevices can self-actuate when exposed to the elevated temperature of a cancerous tumor region, allowing for direct targeting for biopsies. Microgrippers can also be doped to become magnetically responsive, allowing for direction without tethers and the retrieval of microdevices containing excised tissue. The smaller size of stimuli-responsive microgrippers allows for their movement through hard-to-reach areas within the body and the successful extraction of intact cells, RNA and DNA. This review discusses the mechanisms of thermal- and magnetic-responsive microdevices and recent advances in microgripper technology to improve minimally invasive surgical techniques.


Assuntos
Hidrogéis , Polímeros , Biópsia , Magnetismo , Procedimentos Cirúrgicos Minimamente Invasivos , Temperatura
11.
Soft Matter ; 18(33): 6148-6156, 2022 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-35968815

RESUMO

Helical micro-swimmers have markedly extended the reach of human beings in numerous fields, ranging from in vitro tasks in lab-on-a-chip to in vivo applications for minimally invasive medicine. The previous studies on the propulsive motility optimization of the micro-swimmers mainly focused on the distinct actuation principles (e.g., chemically powered, magnetic- or ultrasound energy-driven) and paid little attention to the structural design of these swimming machines themselves. The improvements of the structures can assist the externally powered motors in providing propulsion in a tiny scale and satisfy the agile locomotion demands. This paper presents the design, mechanics modeling and available experiments of a novel type of hierarchical helical swimming robot that significantly enhances the motility of the helix-based swimmers. Validated by the resistive force theory, our numerical model can well analyze the mechanical properties with a variety of geometric parameters. The motion performance of the hierarchical and conventional helical structures in low Reynolds regimes is presented, highlighting the advantages of hierarchical swimmers over the existing typical swimmers. In addition, the stability and resilience of the hierarchical swimmers can be maintained at a decent level. Moreover, the variable forward velocity resulting from the combined hierarchical structures is investigated here, which can thereby serve as a reliable design strategy. The proposed hierarchical helical design enables enticing opportunities for various device systems of medical robots and bio-integrated electronics.


Assuntos
Magnetismo , Natação , Humanos , Locomoção
12.
Phys Chem Chem Phys ; 24(33): 19693-19696, 2022 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-35968933

RESUMO

The wide research interest in nano-, micro-, and macromotors is due to the diverse range of applied problems in engineering, biomedicine, and ecology. At the same time, the amount of known mechanisms responsible for the locomotion of motors is limited. Here, we demonstrate a novel method of motor locomotion, which can be contingently called "chemical magnetism". The phenomenon considered here is based on the fact that any current loop in the magnetic field is affected by a force. "Chemical magnet" represents a bimetal surfer swimming at the electrolyte surface. When the redox reaction proceeds, a current loop emerges. That defines the action of the additional magnetic force on the surfer in the non-uniform magnetic field. The magnetic properties of the surfer can be varied in a wide range by changing the concentration of the electrolyte solution, its temperature, and the pair of metals composing the surfer. The phenomenon of "chemical magnetism" considered here widens a list of known mechanisms of motor locomotion.


Assuntos
Campos Magnéticos , Magnetismo , Movimento (Física) , Temperatura
13.
Anal Chim Acta ; 1224: 340207, 2022 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-35998988

RESUMO

Recently, covalent organic frameworks (COFs) as an important class of porous frameworks have been employed in analytical applications owing to their significant inherent properties such as a high specific surface area with modifiable pore size and a robust nature that leads to great stabilities. Also, COFs are flexible in design to deliberate changes in their physical or chemical properties by generating functionalized COFs or COF-based composites. Here, we summarize some important categories of COFs from the point of view of their design and synthetic strategies. Subsequently, the synergistic combination aspects of COFs with other materials such as different types of magnetic, metal/metal oxide nanoparticles, silica, carbon nanomaterials, polymers, polyoxometalates (POMs), metal-organic frameworks (MOFs), and COFs are reviewed. Finally, the recent applications of COFs as efficient sorbents in analytical sample preparation methods including solid-phase extraction (SPE), dispersive solid-phase extraction (dSPE), magnetic solid-phase extraction (MSPE), and solid-phase microextraction (SPME) will be surveyed with emphasis on important factors that lead to increase extraction efficiency. In addition, challenges and obstacles in these approaches are discussed with perspective highlights.


Assuntos
Nanopartículas Metálicas , Estruturas Metalorgânicas , Magnetismo , Estruturas Metalorgânicas/química , Polímeros/química , Extração em Fase Sólida
14.
Artigo em Inglês | MEDLINE | ID: mdl-35955097

RESUMO

(1) Background: The influence of serotonin on many regulatory mechanisms has not been sufficiently studied. The use of a physical method, assuming the possibility of its action on increasing the concentration of serotonin, may be the direction of therapy limiting the number of antidepressants used. The aim of the research was to study the effects of low-frequency magnetic fields of different characteristics on the circadian profile of serotonin in men with low back pain. (2) Methods: 16 men with back pain syndrome participated in the study. The patients were divided into two groups. In group 1, magnetotherapy (2.9 mT, 40 Hz, square wave, bipolar) was applied at 10.00 a.m. In group 2, the M2P2 magnetic stimulation program of the Viofor JPS device was used. Treatments in each group lasted 3 weeks, 5 days each, with breaks for Saturday and Sunday. The daily serotonin profile was determined the day before the exposure and the day after the last treatment. Blood samples (at night with red light) were collected at 8:00, 12:00, 16:00, 24:00, and 4:00. The patients did not suffer from any chronic or acute disease and were not taking any medications. (3) Results: In group 1, a significant increase in serotonin concentration was observed after 15 treatments at 4:00. In group 2, a significant increase in serotonin concentration was observed at 8:00 after the end of the treatments. In comparison between magnetotherapy and magnetic stimulation, the time points at which differences appeared after the application of serotonin occurred due to the increase in its concentrations after the application of magnetic stimulation. (4) Conclusions: Magnetotherapy and magnetic stimulation, acting in a similar way, increase the concentration of serotonin. Weak magnetic fields work similarly to the stronger ones used in TMS. It is possible to use them in the treatment of mental disorders or other diseases with low serotonin concentrations.


Assuntos
Dor Lombar , Magnetoterapia , Humanos , Dor Lombar/terapia , Campos Magnéticos , Magnetismo , Masculino , Serotonina
15.
Int J Mol Sci ; 23(15)2022 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-35955614

RESUMO

The structural, morphological and magnetic properties of MFe2O4 (M = Co, Ni, Zn, Cu, Mn) type ferrites produced by thermal decomposition at 700 and 1000 °C were studied. The thermal analysis revealed that the ferrites are formed at up to 350 °C. After heat treatment at 1000 °C, single-phase ferrite nanoparticles were attained, while after heat treatment at 700 °C, the CoFe2O4 was accompanied by Co3O4 and the MnFe2O4 by α-Fe2O3. The particle size of the spherical shape in the nanoscale region was confirmed by transmission electron microscopy. The specific surface area below 0.5 m2/g suggested a non-porous structure with particle agglomeration that limits nitrogen absorption. By heat treatment at 1000 °C, superparamagnetic CoFe2O4 nanoparticles and paramagnetic NiFe2O4, MnFe2O4, CuFe2O4 and ZnFe2O4 nanoparticles were obtained.


Assuntos
Cobalto , Magnetismo , Cobalto/química , Fenômenos Magnéticos , Óxidos , Zinco/química
16.
Acta Crystallogr B Struct Sci Cryst Eng Mater ; 78(Pt 4): 589-592, 2022 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-35975825

RESUMO

A new compound, Ba3Ga2O5Cl2, isostructural with Ba3Fe2O5Cl2, was synthesized by solid-state reaction in air. Through single-crystal and powder X-ray diffraction analysis, the crystal structure was determined to be cubic with chiral space group I213 and unit-cell parameter a = 9.928 (1) Å. The Ga3+ ions in Ba3Ga2O5Cl2 are coordinated by O atoms and form GaO4 tetrahedra. Ten neighboring GaO4 tetrahedra are further bridged through corner sharing and rotation along the body diagonal, producing the chiral structure. Magnetization measurements indicate temperature-independent diamagnetic behavior, which is qualitatively consistent with core diamagnetism from all the constituent elements.


Assuntos
Fenômenos Magnéticos , Magnetismo , Cristalografia por Raios X , Fenômenos Físicos
17.
Neuroimage ; 261: 119498, 2022 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-35917918

RESUMO

Increased static field inhomogeneities are a burden for human brain MRI at Ultra-High-Field. In particular they cause enhanced Echo-Planar image distortions and signal losses due to magnetic susceptibility gradients at air-tissue interfaces in the subject's head. In the past decade, Multi-Coil Arrays (MCA) have been proposed to shim the field in the brain better than the 2nd or 3rd order Spherical Harmonic (SH) coils usually offered by MRI manufacturers. Here we present a novel MCA, named SCOTCH, optimized for whole brain shimming. Based on a cylindrical structure, it features several layers of small coils whose shape, size and location are found from a principal component analysis of ideal stream functions computed from an internal 100-brain fieldmap database. From an Open-Access external database of 126 brains, our SCOTCH implementation is shown to be equivalent to a partial 7th-order SH system with unlimited power, outperforming all known existing MCA prototypes. This result is further confirmed by a low-cost  30-cm diameter SCOTCH prototype built with 48 coils on 3 layers, and tested on 7 volunteers at 7T with a parallel-transmit RF coil made to be inserted in SCOTCH. Echo-Planar images of the subject brains before and after SCOTCH shimming show large signal recoveries, especially in the prefrontal cortex.


Assuntos
Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , Encéfalo/diagnóstico por imagem , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Magnetismo , Ondas de Rádio
18.
Biomater Adv ; 140: 213048, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35939957

RESUMO

Helical magnetic nanomotors can be actuated using an external magnetic field and have potential applications in drug delivery, colloidal manipulation, and bio-microrheology. Recently, they have been maneuvered in biological environments such as vitreous humour, dentinal tubules, peritoneal fluid, stromal matrix, and blood, which are promising developments for clinical applications. However, their biocompatibility and biodistribution are vital parameters that must be assessed before further use. An extensive quantitative evaluation has been performed for these parameters for the first time through in vitro and in vivo experiments. Investigations of cell death, proliferation, and DNA damage ascertain that the motors are non-toxic. Also, an unbiased transcriptomic analysis affirms that the motors are not genotoxic till 20 motors/ cell. Toxicity studies in mice reveal that the motors show no signs of toxicity up to a dose of 55 mg/ kg body weight. Further, the biodistribution studies show that they remain in the blood circulation after injection and at later stages possibly adhere to the walls of the blood vessel because of adsorption. However, perfusion with physiological saline decreases this adsorption/adhesion. Overall, we demonstrate the biocompatibility of nanomotors in live cellular and organismal systems, and a systemic biodistribution analysis reveals organ-specific retention of motors.


Assuntos
Campos Magnéticos , Magnetismo , Animais , Camundongos , Distribuição Tecidual
19.
ACS Appl Mater Interfaces ; 14(33): 38291-38301, 2022 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-35971645

RESUMO

Cilia are fundamental functional structures in natural biology. As the primary option of artificial cilia, magnetic cilia have been drawing extensive attention due to their excellent biocompatibility, sensitive response, and contactless actuation. However, most of the ordered magnetic cilia are fabricated by molds, suffering from high cost and low efficiency. In this paper, an ultrafast fabrication method of ordered cilia array using the micro-cavity inducing effect was proposed. With the impact of static and dynamic magnetic fields, the fine cilia were first formed in out-cavity area and then converged above cavities forming complete cilia structures. The mechanism of the micro-cavity inducing effect was further revealed. Finally, the ordered cilia array was used to develop the pressure sensor with variable stiffness, making the in situ adjustment of the sensor performance possible. The ordered cilia array was applied as a micro-mixer and largely improved the mixing efficiency for different mediums. The ordered cilia array also successfully served as the info carrier for rapid sub-encryption. This method allows the fast and controlled forming of ordered cilia arrays within 30 s, and the cilia structure can be adjusted in a large range of aspect ratios (1-9), providing an approach to large-scale producing the magnetic cilia for different applications.


Assuntos
Cílios , Magnetismo , Cílios/fisiologia , Campos Magnéticos
20.
Mikrochim Acta ; 189(9): 340, 2022 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-35995957

RESUMO

Covalent organic framework (COF)-decorated magnetic nanoparticles (Fe3O4@DhaTab) with core-shell structure have been synthesized by one-pot method. The prepared Fe3O4@DhaTab was well characterized, and parameters of magnetic solid-phase extraction (MSPE) for parabens were also investigated in detail. Under optimized conditions, the adsorbent dosage was only 3 mg and extraction time was 10 min. The developed Fe3O4@DhaTab-based MSPE-HPLC analysis method offered good linearity (0.01-20 µg mL-1) with R2 (0.999) and low limits of detection (3.3-6.5 µg L-1) using UV detector at 254 nm. The proposed method was applied to determine four parabens in environmental water samples with recoveries in the range 64.0-105% and relative standard deviations of 0.16-7.8%. The adsorption mechanism was explored and indicated that porous DhaTab shell provided π-π, hydrophobic, and hydrogen bonding interactions in the MSPE process. The results revealed the potential of magnetic-functionalized COFs in determination of environmental contaminants.


Assuntos
Estruturas Metalorgânicas , Cromatografia Líquida de Alta Pressão , Fenômenos Magnéticos , Magnetismo/métodos , Estruturas Metalorgânicas/química , Parabenos
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