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1.
Ultrason Sonochem ; 104: 106810, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38377804

RESUMO

The role of acoustic cavitation in various surface cleaning disciplines is important. However, the physical mechanisms underlying acoustic cavitation-induced surface cleansing are poorly understood. This is due to the combination of microscopic and ultrashort timescales associated with the dynamics of acoustic cavitation bubbles. Here, we have precisely controlled single-bubble cavitation in both space and time. Ultrasonic excitation leads to the cavitation of generated single bubbles. A synchronous ultrafast photomicrographic system simultaneously records the dynamics of single acoustic cavitation bubbles (SACBs) and the cleaning process of the nearby surface in liquids with varying viscosities. Finally, we analysed the correlation between bubble dynamics and surface cleaning situations. The differences in the typical dynamic characteristics of the bubbles during collapse in liquids with varying viscosities reveal two main mechanisms underlying surface cleaning by acoustic cavitation, which are respective the Laplace pressure during the bubble's movement and liquid jets during bubble collapse. Our study provides a better physical understanding of the ultrasonic cleaning process based on acoustic cavitation, and will help to optimize and facilitate the applications of surface cleaning, especially for the cleaning of substrates with tightly attached dirt.

2.
Sensors (Basel) ; 13(5): 5406-47, 2013 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-23615581

RESUMO

The technology of sensor, pervasive computing, and intelligent information processing is widely used in Body Sensor Networks (BSNs), which are a branch of wireless sensor networks (WSNs). BSNs are playing an increasingly important role in the fields of medical treatment, social welfare and sports, and are changing the way humans use computers. Existing surveys have placed emphasis on the concept and architecture of BSNs, signal acquisition, context-aware sensing, and system technology, while this paper will focus on sensor, data fusion, and network communication. And we will introduce the research status of BSNs, the analysis of hotspots, and future development trends, the discussion of major challenges and technical problems facing currently. The typical research projects and practical application of BSNs are introduced as well. BSNs are progressing along the direction of multi-technology integration and intelligence. Although there are still many problems, the future of BSNs is fundamentally promising, profoundly changing the human-machine relationships and improving the quality of people's lives.


Assuntos
Redes de Comunicação de Computadores/instrumentação , Corpo Humano , Tecnologia sem Fio/instrumentação , Humanos , Sistemas Homem-Máquina
3.
Biosensors (Basel) ; 14(1)2023 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-38248394

RESUMO

Sweat, commonly referred to as the ultrafiltrate of blood plasma, is an essential physiological fluid in the human body. It contains a wide range of metabolites, electrolytes, and other biologically significant markers that are closely linked to human health. Compared to other bodily fluids, such as blood, sweat offers distinct advantages in terms of ease of collection and non-invasive detection. In recent years, considerable attention has been focused on wearable sweat sensors due to their potential for continuous monitoring of biomarkers. Electrochemical methods have been extensively used for in situ sweat biomarker analysis, as thoroughly reviewed by various researchers. This comprehensive review aims to provide an overview of recent advances in non-electrochemical methods for analyzing sweat, including colorimetric methods, fluorescence techniques, surface-enhanced Raman spectroscopy, and more. The review covers multiple aspects of non-electrochemical sweat analysis, encompassing sweat sampling methodologies, detection techniques, signal processing, and diverse applications. Furthermore, it highlights the current bottlenecks and challenges faced by non-electrochemical sensors, such as limitations and interference issues. Finally, the review concludes by offering insights into the prospects for non-electrochemical sensing technologies. By providing a valuable reference and inspiring researchers engaged in the field of sweat sensor development, this paper aspires to foster the creation of innovative and practical advancements in this domain.


Assuntos
Leitura , Suor , Humanos , Biomarcadores , Colorimetria , Técnicas Eletroquímicas
4.
ACS Sens ; 8(1): 176-186, 2023 01 27.
Artigo em Inglês | MEDLINE | ID: mdl-36604942

RESUMO

Wearable sweat sensors, a product of the development of flexible electronics and microfluidic technologies, can continuously and noninvasively monitor abundant biomarkers in human sweat; however, sweat interferences, such as sebum, can reduce sensor reliability and accuracy. Herein, for the first time, the influence of sebum on the potentiometric response of an all-solid-state pH sensor was studied, and the obtained experimental results show that sebum mixed in sweat can decrease the potential response of the sensor and the slope of its calibration curve. A paper-based sandwich-structured pH sensor that can filter the sebum mixed in sweat was proposed based on commonly used oil-control sheets. Moreover, the hydrophilic properties, microstructure, and microfluidic performance of the sensor were investigated. The detection performance of the paper-based sandwich-structured pH sensor was comprehensively evaluated in terms of calibration in the presence of sebum and potentiometric response upon the addition of sebum. Furthermore, the anti-interference ability of the sensor was evaluated using different analytes under various deformation conditions. On-body trials were conducted to verify the performance, and their results showed that the proposed sensor can filter over 90% of the sebum in sweat, significantly enhancing sensor reliability and accuracy. Additionally, microfluidic channels could be simply fabricated using a scissor and paper, obviating the need for complex micromachining processes, such as photolithography and laser engraving. Overall, this work illustrates the influence of sebum on the detection performance of traditional potentiometric wearable sensors and paves the way for their development for real-world applications.


Assuntos
Suor , Dispositivos Eletrônicos Vestíveis , Humanos , Suor/química , Sebo , Reprodutibilidade dos Testes , Concentração de Íons de Hidrogênio
5.
Micromachines (Basel) ; 14(8)2023 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-37630034

RESUMO

Human sweat is intricately linked to human health, and unraveling its secrets necessitates a substantial volume of experimental data. However, conventional sensors fabricated via complex processes such as photolithography offer high detection precision at the expense of prohibitive costs. In this study, we presented a cost-effective and high-performance wearable flexible sweat sensor for real-time monitoring of K+ and Na+ concentrations in human sweat, fabricated using screen printing technology. Initially, we evaluated the electrical and electrochemical stability of the screen-printed substrate electrodes, which demonstrated good consistency with a variation within 10% of the relative standard deviation (RSD), meeting the requirements for reliable detection of K+ and Na+ in human sweat. Subsequently, we employed an "ion-electron" transduction layer and an ion-selective membrane to construct the sensors for detecting K+ and Na+. Comprehensive tests were conducted to assess the sensors' sensitivity, linearity, repeatability, resistance to interference, and mechanical deformation capabilities. Furthermore, we evaluated their long-term stability during continuous monitoring and storage. The test results confirmed that the sensor's performance indicators, as mentioned above, met the requirements for analyzing human sweat. In a 10-day continuous and regular monitoring experiment involving volunteers wearing the sensors, a wealth of data revealed a close relationship between K+ and Na+ concentrations in human sweat and hydration status. Notably, we observed that consistent and regular physical exercise effectively enhanced the body's resistance to dehydration. These findings provided a solid foundation for conducting extensive experiments and further exploring the intricate relationship between human sweat and overall health. Our research paved a practical and feasible path for future studies in this domain.

6.
Ultrason Sonochem ; 101: 106690, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37948892

RESUMO

As a safe and effective method for systemic transdermal drug delivery (TDD), sonophoresis has drawn much attention from researchers. Despite numerous studies confirming cavitation as the main reason for sonophoresis, the effect skin has on cavitation bubble dynamics remains elusive due to the difficulty of experimental challenges. For a start, we reveal how single cavitation bubble (SCB) dynamics are affected by skin properties, including elasticity, hydrophilicity and texture. We use polydimethylsiloxane (PDMS) to simulate human skin and record the temporary evolution of SCBs with synchronous ultrafast photography. The influences of skin properties on SCBs are concluded: 1) SCBs collapse later near walls with better elasticities and generate microjets with higher speed; 2) SCBs collapse later near hydrophilic walls with slower microjets; and 3) the existence of a texture structure on walls also delays the time of bubble collapse near them and slows the velocities of microjets (v) during collapses.


Assuntos
Fotografação , Humanos , Administração Cutânea , Interações Hidrofóbicas e Hidrofílicas
7.
Micromachines (Basel) ; 13(12)2022 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-36557355

RESUMO

Microfluidics technology plays an important role in modern analytical instruments, while the modular design of microfluidics facilitates the reconfiguration of analytical instrument functions, making it possible to deploy on-demand systems in the field. However, modular design also faces the challenges such as connection reliability and reconfiguration convenience. Inspired by the self-locking structure of the Rubik's cube, a modular, reconfigurable microfluidic instrument architecture is proposed in this paper. The system has a self-locking structure of Rubik's cube components and an O-ring-based alignment and sealing mechanism, which enables reliable interconnection and rapid rearrangement of microfluidic modules by simply rotating the faces of the microfluidic cube. In addition, the system is capable of integrating a variety of customized modules to perform analysis tasks. A proof-of-concept application of detecting multiple pollutants in water is demonstrated to show the reconfigurable characteristics of the system. The findings of this paper provide a new idea for the design of microfluidic analytical instrument architectures.

8.
Micromachines (Basel) ; 13(8)2022 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-36014285

RESUMO

This review mainly studies the development status, limitations, and future directions of modular microfluidic systems. Microfluidic technology is an important tool platform for scientific research and plays an important role in various fields. With the continuous development of microfluidic applications, conventional monolithic microfluidic chips show more and more limitations. A modular microfluidic system is a system composed of interconnected, independent modular microfluidic chips, which are easy to use, highly customizable, and on-site deployable. In this paper, the current forms of modular microfluidic systems are classified and studied. The popular fabrication techniques for modular blocks, the major application scenarios of modular microfluidics, and the limitations of modular techniques are also discussed. Lastly, this review provides prospects for the future direction of modular microfluidic technologies.

9.
Biomicrofluidics ; 16(3): 031503, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35757146

RESUMO

Bubbles in microfluidics-even those that appear to be negligibly small-are pervasive and responsible for the failure of many biological and chemical experiments. For instance, they block current conduction, damage cell membranes, and interfere with detection results. To overcome this unavoidable and intractable problem, researchers have developed various methods for capturing and removing bubbles from microfluidics. Such methods are multifarious and their working principles are very different from each other. In this review, bubble-removing methods are divided into two broad categories: active debubblers (that require external auxiliary equipment) and passive debubblers (driven by natural processes). In each category, three main types of methods are discussed along with their advantages and disadvantages. Among the active debubblers, those assisted by lasers, acoustic generators, and negative pressure pumps are discussed. Among the passive debubblers, those driven by buoyancy, the characteristics of gas-liquid interfaces, and the hydrophilic and hydrophobic properties of materials are discussed. Finally, the challenges and prospects of the bubble-removal technologies are reviewed to refer researchers to microfluidics and inspire further investigations in this field.

10.
Micromachines (Basel) ; 13(5)2022 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-35630249

RESUMO

The motion of bubbles in an ultrasonic field is a fundamental physical mechanism in most applications of acoustic cavitation. In these applications, surface-active solutes, which could lower the surface tension of the liquid, are always utilized to improve efficiency by reducing the cavitation threshold. This paper examines the influence of liquids' surface tension on single micro-bubbles motion in an ultrasonic field. A novel experimental system based on high-speed photography has been designed to investigate the temporary evolution of a single bubble in the free-field exposed to a 20.43 kHz ultrasound in liquids with different surface tensions. In addition, the R-P equations in the liquid with different surface tension are solved. It is found that the influences of the surface tension on the bubble dynamics are obvious, which reflect on the changes in the maximum size and speed of the bubble margin during bubble oscillating, as well as the weaker stability of the bubble in the liquid with low surface tension, especially for the oscillating bubble with higher speed. These effects of the surface tension on the bubble dynamics can explain the mechanism of surfactants for promoting acoustic cavitation in numerous application fields.

11.
ACS Appl Mater Interfaces ; 12(1): 1817-1824, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31804059

RESUMO

This paper presents a novel method of rapidly customizing microfluidic systems using a consumer-grade inkjet printer and a commercially available superhydrophobic spray. By casting polydimethylsiloxane (PDMS) on liquid templates that are defined by inkjet-printed hydrophilic patterns on superhydrophobically-coated PDMS substrates, microfluidic devices can be directly fabricated. Utilizing the interfacial properties of the superhydrophobic coating and the template liquid, the fabrication of microfluidics could be done with minimum effort and expertise, and unlike previously reported works, no mask and bonding process is necessary. As a proof of concept, we created different microfluidic devices for various applications, like gradient generation and pneumatic control of fluid. Appealing in its simplicity and rapidness, the newly proposed technique could provide an easy-to-use microfluidic platform for front-line researchers with different backgrounds to quickly customize microfluidic devices.

12.
Microsyst Nanoeng ; 6: 27, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-34567642

RESUMO

A Rubik's cube as a reconfigurable microfluidic system is presented in this work. Composed of physically interlocking microfluidic blocks, the microfluidic cube enables the on-site design and configuration of custom microfluidics by twisting the faces of the cube. The reconfiguration of the microfluidics could be done by solving an ordinary Rubik's cube with the help of Rubik's cube algorithms and computer programs. An O-ring-aided strategy is used to enable self-sealing and the automatic alignment of the microfluidic cube blocks. Owing to the interlocking mechanics of cube blocks, the proposed microfluidic cube exhibits good reconfigurability and robustness in versatile applications and proves to be a promising candidate for the rapid deployment of microfluidic systems in resource-limited settings.

13.
Ultrason Sonochem ; 68: 105197, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32570003

RESUMO

Bubble behaviors near a boundary in an ultrasonic field are the fundamental forms of acoustic cavitation and of substantial importance in various applications, such as industry cleaning, chemical engineering and food processing. The effects of two important factors that strongly affect the dynamics of a single acoustic cavitation bubble, namely, the initial bubble radius and the standoff distance, were investigated in this work. The temporal evolution of the bubble was recorded using high speed microphotography. Meanwhile, the time of bubble collapse and the characteristics of the liquid jets were analyzed. The results demonstrate that the intensity of the acoustic cavitation, which is characterized by the time of bubble collapse and the liquid jet speed, reaches the optimum level under suitable values of the initial bubble radius and the normalized standoff distance. As the initial bubble radius and the normalized standoff distance increase or decrease from the optimal values, the time of the bubble collapse increases, and the first liquid jet's speed decreases substantially, whereas the speeds of the second and third liquid jets exhibit no substantial changes. These results on bubble dynamics in an ultrasonic field are important for identifying or correcting the mechanisms of acoustic cavitation and for facilitating its optimization and application.

14.
Chem Commun (Camb) ; 56(64): 9056-9066, 2020 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-32744276

RESUMO

The droplet-based microfluidic techniques have been applied widely in functional material synthesis and biomedical information measurements, wherein step emulsification as an integrated system combines the advantages of homogeneity and throughput in monodisperse droplet formation. This paper reviews the mechanisms and classical structures of step emulsification. In terms of droplet formation mechanisms, we describe the droplet size and detachment regimes related to the microchannel geometry. Distinguished by droplet formation, microfluidic step emulsification driven by interfacial tension and centrifugal step emulsification related to buoyancy are introduced respectively, including their improved structures for enhancing the droplet homogeneity and throughput. Finally, the perspectives about the developments of step emulsification in mechanisms, fabrications, and applications are discussed.

15.
ACS Biomater Sci Eng ; 5(12): 6801-6810, 2019 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-33423473

RESUMO

This paper proposes a novel strategy and an all-in-one toolbox that allows instrument-free customization of integrated microfluidic systems. Unlike the modular design of combining multiple microfluidic chips in the previous literature, this work, for the first time, proposes a "template sticker" method, in which sacrificial templates for microfluidic components are batch-produced in the form of standardized stickers and packaged into a toolbox. To create a customized monolithic microfluidic system, the end users only need to select and combine various template stickers following formulated steps. The fabricated microfluidic devices have well-defined microscale features, while the fabrication process is inexpensive and time-saving. Various functional microfluidic devices were fabricated and tested using this toolbox. The capability to create microchannels on curved surfaces is also demonstrated. As a proof of concept, we developed with the proposed toolbox a colorimetric testing platform for the detection of nitrite ions. The sticker toolbox, as the first self-contained portable platform for microfluidic fabrication, allows prompt customization of monolithic devices, enabling deployment of microfluidics with both ideal performance and customizability.

16.
Biomicrofluidics ; 10(1): 011910, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26958097

RESUMO

This paper presents a continuous glucose monitoring microsystem consisting of a three-electrode electrochemical sensor integrated into a microfluidic chip. The microfluidic chip, which was used to transdermally extract and collect subcutaneous interstitial fluid, was fabricated from five polydimethylsiloxane layers using micromolding techniques. The electrochemical sensor was integrated into the chip for continuous detection of glucose. Specifically, a single-layer graphene and gold nanoparticles (AuNPs) were decorated onto the working electrode (WE) of the sensor to construct a composite nanostructured surface and improve the resolution of the glucose measurements. Graphene was transferred onto the WE surface to improve the electroactive nature of the electrode to enable measurements of low levels of glucose. The AuNPs were directly electrodeposited onto the graphene layer to improve the electron transfer rate from the activity center of the enzyme to the electrode to enhance the sensitivity of the sensor. Glucose oxidase (GOx) was immobilized onto the composite nanostructured surface to specifically detect glucose. The factors required for AuNPs deposition and GOx immobilization were also investigated, and the optimized parameters were obtained. The experimental results displayed that the proposed sensor could precisely measure glucose in the linear range from 0 to 162 mg/dl with a detection limit of 1.44 mg/dl (S/N = 3). The proposed sensor exhibited the potential to detect hypoglycemia which is still a major challenge for continuous glucose monitoring in clinics. Unlike implantable glucose sensors, the wearable device enabled external continuous monitoring of glucose without interference from foreign body reaction and bioelectricity.

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