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Search Results (3,353)

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4616 KiB  
Article
Applications of Information and Communication Technology for Improvements of Water and Soil Monitoring and Assessments in Agricultural Areas—A Case Study in the Taoyuan Irrigation District
by Yu-Pin Lin, Tsun-Kuo Chang, Chihhao Fan, Johnathen Anthony, Joy R. Petway, Wan-Yu Lien, Chiu-Ping Liang and Yi-Fong Ho
Environments 2017, 4(1), 6; https://doi.org/10.3390/environments4010006 - 17 Jan 2017
Cited by 12 | Viewed by 7546
Abstract
In order to guarantee high-quality agricultural products and food safety, efforts must be made to manage and maintain healthy agricultural environments under the myriad of risks that they face. Three central system components of sustainable agricultural management schemes are real-time monitoring, decision-making, and [...] Read more.
In order to guarantee high-quality agricultural products and food safety, efforts must be made to manage and maintain healthy agricultural environments under the myriad of risks that they face. Three central system components of sustainable agricultural management schemes are real-time monitoring, decision-making, and remote access. Information and Communications Technology (ICT) systems are a convenient means of providing both these and other functions, such as wireless sensor networking, mobile phone applications, etc., to agricultural management schemes. ICT systems have significantly improved in recent years and have been widely used in many fields, including environmental monitoring and management. Moreover, ICT could benefit agricultural environment management by providing a platform for collaboration between researchers and stakeholders, thereby improving agricultural practices and environments. This article reviews and discusses the way in which ICT can efficiently improve monitoring systems and risk assessments of agricultural environment monitoring, as well as the technological and methodological improvements of ICT systems. Finally, we develop and apply an ICT system, referred to as the agricultural environment protection system—comprised of a cloud, six E-platforms, three mobile devices, automatic monitoring devices, indigenous wireless sensor nodes, and gateways in agricultural networks—to a case study in the Taoyuan irrigation district, which acts as a pilot area in Taiwan. Through the system, we use all available information from the interdisciplinary structured cloud database to classify the focal area into different agricultural environmental risk zones. We also conducted further analysis based on a hierarchical approach in order to classify the agricultural environments in the study area, to allocate additional sampling with resin packages and mobile devices, as well as to assist decision makers and stakeholders. The main contributions that the system provides include a technical innovation platform (suitable for integrating innovations), economic benefits, and societal benefits. Full article
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4375 KiB  
Article
Odor-Sensing System to Support Social Participation of People Suffering from Incontinence
by Alvaro Ortiz Pérez, Vera Kallfaß-de Frenes, Alexander Filbert, Janosch Kneer, Benedikt Bierer, Pirmin Held, Philipp Klein, Jürgen Wöllenstein, Dirk Benyoucef, Sigrid Kallfaß, Ulrich Mescheder and Stefan Palzer
Sensors 2017, 17(1), 58; https://doi.org/10.3390/s17010058 - 29 Dec 2016
Cited by 11 | Viewed by 8252
Abstract
This manuscript describes the design considerations, implementation, and laboratory validation of an odor sensing module whose purpose is to support people that suffer from incontinence. Because of the requirements expressed by the affected end-users the odor sensing unit is realized as a portable [...] Read more.
This manuscript describes the design considerations, implementation, and laboratory validation of an odor sensing module whose purpose is to support people that suffer from incontinence. Because of the requirements expressed by the affected end-users the odor sensing unit is realized as a portable accessory that may be connected to any pre-existing smart device. We have opted for a low-cost, low-power consuming metal oxide based gas detection approach to highlight the viability of developing an inexpensive yet helpful odor recognition technology. The system consists of a hotplate employing, inkjet-printed p-type semiconducting layers of copper(II) oxide, and chromium titanium oxide. Both functional layers are characterized with respect to their gas-sensitive behavior towards humidity, ammonia, methylmercaptan, and dimethylsulfide and we demonstrate detection limits in the parts-per-billion range for the two latter gases. Employing a temperature variation scheme that reads out the layer’s resistivity in a steady-state, we use each sensor chip as a virtual array. With this setup, we demonstrate the feasibility of detecting odors associated with incontinence. Full article
(This article belongs to the Special Issue Olfactory and Gustatory Sensors)
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17523 KiB  
Article
Sensing Technologies for Autism Spectrum Disorder Screening and Intervention
by John-John Cabibihan, Hifza Javed, Mohammed Aldosari, Thomas W. Frazier and Haitham Elbashir
Sensors 2017, 17(1), 46; https://doi.org/10.3390/s17010046 - 27 Dec 2016
Cited by 54 | Viewed by 12167
Abstract
This paper reviews the state-of-the-art in sensing technologies that are relevant for Autism Spectrum Disorder (ASD) screening and therapy. This disorder is characterized by difficulties in social communication, social interactions, and repetitive behaviors. It is diagnosed during the first three years of life. [...] Read more.
This paper reviews the state-of-the-art in sensing technologies that are relevant for Autism Spectrum Disorder (ASD) screening and therapy. This disorder is characterized by difficulties in social communication, social interactions, and repetitive behaviors. It is diagnosed during the first three years of life. Early and intensive interventions have been shown to improve the developmental trajectory of the affected children. The earlier the diagnosis, the sooner the intervention therapy can begin, thus, making early diagnosis an important research goal. Technological innovations have tremendous potential to assist with early diagnosis and improve intervention programs. The need for careful and methodological evaluation of such emerging technologies becomes important in order to assist not only the therapists and clinicians in their selection of suitable tools, but to also guide the developers of the technologies in improving hardware and software. In this paper, we survey the literatures on sensing technologies for ASD and we categorize them into eye trackers, movement trackers, electrodermal activity monitors, tactile sensors, vocal prosody and speech detectors, and sleep quality assessment devices. We assess their effectiveness and study their limitations. We also examine the challenges faced by this growing field that need to be addressed before these technologies can perform up to their theoretical potential. Full article
(This article belongs to the Special Issue Sensing Technology for Healthcare System)
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1518 KiB  
Article
An Indoor Positioning System Based on Wearables for Ambient-Assisted Living
by Óscar Belmonte-Fernández, Adrian Puertas-Cabedo, Joaquín Torres-Sospedra, Raúl Montoliu-Colás and Sergi Trilles-Oliver
Sensors 2017, 17(1), 36; https://doi.org/10.3390/s17010036 - 25 Dec 2016
Cited by 65 | Viewed by 9109
Abstract
The urban population is growing at such a rate that by 2050 it is estimated that 84% of the world’s population will live in cities, with flats being the most common living place. Moreover, WiFi technology is present in most developed country urban [...] Read more.
The urban population is growing at such a rate that by 2050 it is estimated that 84% of the world’s population will live in cities, with flats being the most common living place. Moreover, WiFi technology is present in most developed country urban areas, with a quick growth in developing countries. New Ambient-Assisted Living applications will be developed in the near future having user positioning as ground technology: elderly tele-care, energy consumption, security and the like are strongly based on indoor positioning information. We present an Indoor Positioning System for wearable devices based on WiFi fingerprinting. Smart-watch wearable devices are used to acquire the WiFi strength signals of the surrounding Wireless Access Points used to build an ensemble of Machine Learning classification algorithms. Once built, the ensemble algorithm is used to locate a user based on the WiFi strength signals provided by the wearable device. Experimental results for five different urban flats are reported, showing that the system is robust and reliable enough for locating a user at room level into his/her home. Another interesting characteristic of the presented system is that it does not require deployment of any infrastructure, and it is unobtrusive, the only device required for it to work is a smart-watch. Full article
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3635 KiB  
Article
Body-Machine Interfaces after Spinal Cord Injury: Rehabilitation and Brain Plasticity
by Ismael Seáñez-González, Camilla Pierella, Ali Farshchiansadegh, Elias B. Thorp, Xue Wang, Todd Parrish and Ferdinando A. Mussa-Ivaldi
Brain Sci. 2016, 6(4), 61; https://doi.org/10.3390/brainsci6040061 - 19 Dec 2016
Cited by 16 | Viewed by 7509
Abstract
The purpose of this study was to identify rehabilitative effects and changes in white matter microstructure in people with high-level spinal cord injury following bilateral upper-extremity motor skill training. Five subjects with high-level (C5–C6) spinal cord injury (SCI) performed five visuo-spatial motor training [...] Read more.
The purpose of this study was to identify rehabilitative effects and changes in white matter microstructure in people with high-level spinal cord injury following bilateral upper-extremity motor skill training. Five subjects with high-level (C5–C6) spinal cord injury (SCI) performed five visuo-spatial motor training tasks over 12 sessions (2–3 sessions per week). Subjects controlled a two-dimensional cursor with bilateral simultaneous movements of the shoulders using a non-invasive inertial measurement unit-based body-machine interface. Subjects’ upper-body ability was evaluated before the start, in the middle and a day after the completion of training. MR imaging data were acquired before the start and within two days of the completion of training. Subjects learned to use upper-body movements that survived the injury to control the body-machine interface and improved their performance with practice. Motor training increased Manual Muscle Test scores and the isometric force of subjects’ shoulders and upper arms. Moreover, motor training increased fractional anisotropy (FA) values in the cingulum of the left hemisphere by 6.02% on average, indicating localized white matter microstructure changes induced by activity-dependent modulation of axon diameter, myelin thickness or axon number. This body-machine interface may serve as a platform to develop a new generation of assistive-rehabilitative devices that promote the use of, and that re-strengthen, the motor and sensory functions that survived the injury. Full article
(This article belongs to the Special Issue Motor Control and Brain Plasticity)
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2566 KiB  
Review
Label-Free Aptasensors for the Detection of Mycotoxins
by Amina Rhouati, Gaelle Catanante, Gilvanda Nunes, Akhtar Hayat and Jean-Louis Marty
Sensors 2016, 16(12), 2178; https://doi.org/10.3390/s16122178 - 18 Dec 2016
Cited by 78 | Viewed by 10728
Abstract
Various methodologies have been reported in the literature for the qualitative and quantitative monitoring of mycotoxins in food and feed samples. Based on their enhanced specificity, selectivity and versatility, bio-affinity assays have inspired many researchers to develop sensors by exploring bio-recognition phenomena. However, [...] Read more.
Various methodologies have been reported in the literature for the qualitative and quantitative monitoring of mycotoxins in food and feed samples. Based on their enhanced specificity, selectivity and versatility, bio-affinity assays have inspired many researchers to develop sensors by exploring bio-recognition phenomena. However, a significant problem in the fabrication of these devices is that most of the biomolecules do not generate an easily measurable signal upon binding to the target analytes, and signal-generating labels are required to perform the measurements. In this context, aptamers have been emerged as a potential and attractive bio-recognition element to design label-free aptasensors for various target analytes. Contrary to other bioreceptor-based approaches, the aptamer-based assays rely on antigen binding-induced conformational changes or oligomerization states rather than binding-assisted changes in adsorbed mass or charge. This review will focus on current designs in label-free conformational switchable design strategies, with a particular focus on applications in the detection of mycotoxins. Full article
(This article belongs to the Special Issue Aptasensors 2016)
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2015 KiB  
Article
Green Small Cell Operation of Ultra-Dense Networks Using Device Assistance
by Gilsoo Lee and Hongseok Kim
Energies 2016, 9(12), 1065; https://doi.org/10.3390/en9121065 - 16 Dec 2016
Cited by 4 | Viewed by 3493
Abstract
As higher performance is demanded in 5G networks, energy consumption in wireless networks increases along with the advances of various technologies, so enhancing energy efficiency also becomes an important goal to implement 5G wireless networks. In this paper, we study the energy efficiency [...] Read more.
As higher performance is demanded in 5G networks, energy consumption in wireless networks increases along with the advances of various technologies, so enhancing energy efficiency also becomes an important goal to implement 5G wireless networks. In this paper, we study the energy efficiency maximization problem focused on finding a suitable set of turned-on small cell access points (APs). Finding the suitable on/off states of APs is challenging since the APs can be deployed by users while centralized network planning is not always possible. Therefore, when APs in small cells are randomly deployed and thus redundant in many cases, a mechanism of dynamic AP turning-on/off is required. We propose a device-assisted framework that exploits feedback messages from the user equipment (UE). To solve the problem, we apply an optimization method using belief propagation (BP) on a factor graph. Then, we propose a family of online algorithms inspired by BP, called DANCE, that requires low computational complexity. We perform numerical simulations, and the extensive simulations confirm that BP enhances energy efficiency significantly. Furthermore, simple, but practical DANCE exhibits close performance to BP and also better performance than other popular existing methods. Specifically, in a small-sized network, BP enhances energy efficiency 129%. Furthermore, in ultra-dense networks, DANCE algorithms successfully achieve orders of magnitude higher energy efficiency than that of the baseline. Full article
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352 KiB  
Article
Evaluation of Google Glass Technical Limitations on Their Integration in Medical Systems
by Antonio Martinez-Millana, Jose-Luis Bayo-Monton, Aroa Lizondo, Carlos Fernandez-Llatas and Vicente Traver
Sensors 2016, 16(12), 2142; https://doi.org/10.3390/s16122142 - 15 Dec 2016
Cited by 27 | Viewed by 9654
Abstract
Google Glass is a wearable sensor presented to facilitate access to information and assist while performing complex tasks. Despite the withdrawal of Google in supporting the product, today there are multiple applications and much research analyzing the potential impact of this technology in [...] Read more.
Google Glass is a wearable sensor presented to facilitate access to information and assist while performing complex tasks. Despite the withdrawal of Google in supporting the product, today there are multiple applications and much research analyzing the potential impact of this technology in different fields of medicine. Google Glass satisfies the need of managing and having rapid access to real-time information in different health care scenarios. Among the most common applications are access to electronic medical records, display monitorizations, decision support and remote consultation in specialties ranging from ophthalmology to surgery and teaching. The device enables a user-friendly hands-free interaction with remote health information systems and broadcasting medical interventions and consultations from a first-person point of view. However, scientific evidence highlights important technical limitations in its use and integration, such as failure in connectivity, poor reception of images and automatic restart of the device. This article presents a technical study on the aforementioned limitations (specifically on the latency, reliability and performance) on two standard communication schemes in order to categorize and identify the sources of the problems. Results have allowed us to obtain a basis to define requirements for medical applications to prevent network, computational and processing failures associated with the use of Google Glass. Full article
(This article belongs to the Special Issue Sensing Technology for Healthcare System)
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509 KiB  
Review
Technical Developments and Clinical Use of Telemedicine in Sleep Medicine
by Marie Bruyneel
J. Clin. Med. 2016, 5(12), 116; https://doi.org/10.3390/jcm5120116 - 13 Dec 2016
Cited by 10 | Viewed by 6120
Abstract
The use of assistive technology and telemedicine is likely to continue to shape our medical practice in the future, notably in the field of sleep medicine, especially within developed countries. Currently, the number of people suffering from obstructive sleep apnea syndrome (OSAS) is [...] Read more.
The use of assistive technology and telemedicine is likely to continue to shape our medical practice in the future, notably in the field of sleep medicine, especially within developed countries. Currently, the number of people suffering from obstructive sleep apnea syndrome (OSAS) is increasing. Telemedicine (TM) can be used in a variety of ways in sleep medicine: telediagnostics, teleconsultation, teletherapy and telemonitoring of patients being treated with positive pressure devices. In this review, we aim to summarize the recent scientific progresses of these techniques and their potential clinical applications and give consideration to the remaining problems related to TM application. Full article
(This article belongs to the Special Issue Telemedicine - Technical Developments and Clinical Practice)
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1612 KiB  
Review
Mechanical Circulatory Support for Advanced Heart Failure: Are We about to Witness a New “Gold Standard”?
by Massimo Capoccia
J. Cardiovasc. Dev. Dis. 2016, 3(4), 35; https://doi.org/10.3390/jcdd3040035 - 12 Dec 2016
Cited by 24 | Viewed by 7437
Abstract
The impact of left ventricular assist devices (LVADs) for the treatment of advanced heart failure has played a significant role as a bridge to transplant and more recently as a long-term solution for non-eligible candidates. Continuous flow left ventricular assist devices (CF-LVADs), based [...] Read more.
The impact of left ventricular assist devices (LVADs) for the treatment of advanced heart failure has played a significant role as a bridge to transplant and more recently as a long-term solution for non-eligible candidates. Continuous flow left ventricular assist devices (CF-LVADs), based on axial and centrifugal design, are currently the most popular devices in view of their smaller size, increased reliability and higher durability compared to pulsatile flow left ventricular assist devices (PF-LVADs). The trend towards their use is increasing. Therefore, it has become mandatory to understand the physics and the mathematics behind their mode of operation for appropriate device selection and simulation set up. For this purpose, this review covers some of these aspects. Although very successful and technologically advanced, they have been associated with complications such as pump thrombosis, haemolysis, aortic regurgitation, gastro-intestinal bleeding and arterio-venous malformations. There is perception that the reduced arterial pulsatility may be responsible for these complications. A flow modulation control approach is currently being investigated in order to generate pulsatility in rotary blood pumps. Thrombus formation remains the most feared complication that can affect clinical outcome. The development of a preoperative strategy aimed at the reduction of complications and patient-device suitability may be appropriate. Patient-specific modelling based on 3D reconstruction from CT-scan combined with computational fluid dynamic studies is an attractive solution in order to identify potential areas of stagnation or challenging anatomy that could be addressed to achieve the desired outcome. The HeartMate II (axial) and the HeartWare HVAD (centrifugal) rotary blood pumps have been now used worldwide with proven outcome. The HeartMate III (centrifugal) is now emerging as the new promising device with encouraging preliminary results. There are now enough pumps on the market: it is time to focus on the complications in order to achieve the full potential and selling-point of this type of technology for the treatment of the increasing heart failure patient population. Full article
(This article belongs to the Special Issue Heart Failure Pathogenesis and Management)
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1275 KiB  
Review
Polymer Microfluidics: Simple, Low-Cost Fabrication Process Bridging Academic Lab Research to Commercialized Production
by Chia-Wen Tsao
Micromachines 2016, 7(12), 225; https://doi.org/10.3390/mi7120225 - 10 Dec 2016
Cited by 272 | Viewed by 18085
Abstract
Using polymer materials to fabricate microfluidic devices provides simple, cost effective, and disposal advantages for both lab-on-a-chip (LOC) devices and micro total analysis systems (μTAS). Polydimethylsiloxane (PDMS) elastomer and thermoplastics are the two major polymer materials used in microfluidics. The fabrication of PDMS [...] Read more.
Using polymer materials to fabricate microfluidic devices provides simple, cost effective, and disposal advantages for both lab-on-a-chip (LOC) devices and micro total analysis systems (μTAS). Polydimethylsiloxane (PDMS) elastomer and thermoplastics are the two major polymer materials used in microfluidics. The fabrication of PDMS and thermoplastic microfluidic device can be categorized as front-end polymer microchannel fabrication and post-end microfluidic bonding procedures, respectively. PDMS and thermoplastic materials each have unique advantages and their use is indispensable in polymer microfluidics. Therefore, the proper selection of polymer microfabrication is necessary for the successful application of microfluidics. In this paper, we give a short overview of polymer microfabrication methods for microfluidics and discuss current challenges and future opportunities for research in polymer microfluidics fabrication. We summarize standard approaches, as well as state-of-art polymer microfluidic fabrication methods. Currently, the polymer microfluidic device is at the stage of technology transition from research labs to commercial production. Thus, critical consideration is also required with respect to the commercialization aspects of fabricating polymer microfluidics. This article provides easy-to-understand illustrations and targets to assist the research community in selecting proper polymer microfabrication strategies in microfluidics. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics)
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8124 KiB  
Article
An Open Platform for Seamless Sensor Support in Healthcare for the Internet of Things
by Jorge Miranda, Jorge Cabral, Stefan Rahr Wagner, Christian Fischer Pedersen, Blaise Ravelo, Mukhtiar Memon and Morten Mathiesen
Sensors 2016, 16(12), 2089; https://doi.org/10.3390/s16122089 - 8 Dec 2016
Cited by 31 | Viewed by 8759
Abstract
Population aging and increasing pressure on health systems are two issues that demand solutions. Involving and empowering citizens as active managers of their health represents a desirable shift from the current culture mainly focused on treatment of disease, to one also focused on [...] Read more.
Population aging and increasing pressure on health systems are two issues that demand solutions. Involving and empowering citizens as active managers of their health represents a desirable shift from the current culture mainly focused on treatment of disease, to one also focused on continuous health management and well-being. Current developments in technological areas such as the Internet of Things (IoT), lead to new technological solutions that can aid this shift in the healthcare sector. This study presents the design, development, implementation and evaluation of a platform called Common Recognition and Identification Platform (CRIP), a part of the CareStore project, which aims at supporting caregivers and citizens to manage health routines in a seamless way. Specifically, the CRIP offers sensor-based support for seamless identification of users and health devices. A set of initial requirements was defined with a focus on usability limitations and current sensor technologies. The CRIP was designed and implemented using several technologies that enable seamless integration and interaction of sensors and people, namely Near Field Communication and fingerprint biometrics for identification and authentication, Bluetooth for communication with health devices and web services for wider integration with other platforms. Two CRIP prototypes were implemented and evaluated in laboratory during a period of eight months. The evaluations consisted of identifying users and devices, as well as seamlessly configure and acquire vital data from the last. Also, the entire Carestore platform was deployed in a nursing home where its usability was evaluated with caregivers. The evaluations helped assess that seamless identification of users and seamless configuration and communication with health devices is feasible and can help enable the IoT on healthcare applications. Therefore, the CRIP and similar platforms could be transformed into a valuable enabling technology for secure and reliable IoT deployments on the healthcare sector. Full article
(This article belongs to the Special Issue Sensing Technology for Healthcare System)
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1714 KiB  
Article
A Robust and Device-Free System for the Recognition and Classification of Elderly Activities
by Fangmin Li, Mohammed Abdulaziz Aide Al-qaness, Yong Zhang, Bihai Zhao and Xidao Luan
Sensors 2016, 16(12), 2043; https://doi.org/10.3390/s16122043 - 1 Dec 2016
Cited by 31 | Viewed by 6182
Abstract
Human activity recognition, tracking and classification is an essential trend in assisted living systems that can help support elderly people with their daily activities. Traditional activity recognition approaches depend on vision-based or sensor-based techniques. Nowadays, a novel promising technique has obtained more attention, [...] Read more.
Human activity recognition, tracking and classification is an essential trend in assisted living systems that can help support elderly people with their daily activities. Traditional activity recognition approaches depend on vision-based or sensor-based techniques. Nowadays, a novel promising technique has obtained more attention, namely device-free human activity recognition that neither requires the target object to wear or carry a device nor install cameras in a perceived area. The device-free technique for activity recognition uses only the signals of common wireless local area network (WLAN) devices available everywhere. In this paper, we present a novel elderly activities recognition system by leveraging the fluctuation of the wireless signals caused by human motion. We present an efficient method to select the correct data from the Channel State Information (CSI) streams that were neglected in previous approaches. We apply a Principle Component Analysis method that exposes the useful information from raw CSI. Thereafter, Forest Decision (FD) is adopted to classify the proposed activities and has gained a high accuracy rate. Extensive experiments have been conducted in an indoor environment to test the feasibility of the proposed system with a total of five volunteer users. The evaluation shows that the proposed system is applicable and robust to electromagnetic noise. Full article
(This article belongs to the Special Issue New Paradigms in Cyber-Physical Social Sensing)
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5270 KiB  
Article
An Interference-Assisted Thermal Bonding Method for the Fabrication of Thermoplastic Microfluidic Devices
by Yao Gong, Jang Min Park and Jiseok Lim
Micromachines 2016, 7(11), 211; https://doi.org/10.3390/mi7110211 - 22 Nov 2016
Cited by 12 | Viewed by 4411
Abstract
Solutions for the bonding and sealing of micro-channels in the manufacturing process of microfluidic devices are limited; therefore, further technical developments are required to determine these solutions. In this study, a new bonding method for thermoplastic microfluidic devices was developed by combining an [...] Read more.
Solutions for the bonding and sealing of micro-channels in the manufacturing process of microfluidic devices are limited; therefore, further technical developments are required to determine these solutions. In this study, a new bonding method for thermoplastic microfluidic devices was developed by combining an interference fit with a thermal treatment at low pressure. This involved a process of first injection molding thermoplastic substrates with a microchannel structure, and then performing bonding experiments at different bonding conditions. The results indicated the successful bonding of microchannels over a wide range of bonding pressures with the help of the interference fit. The study also determined additional advantages of the proposed bonding method by comparing the method with the conventional thermal bonding method. Full article
(This article belongs to the Special Issue Insights and Advancements in Microfluidics)
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3652 KiB  
Article
Modeling the Link between Left Ventricular Flow and Thromboembolic Risk Using Lagrangian Coherent Structures
by Karen May-Newman, Vi Vu and Brian Herold
Fluids 2016, 1(4), 38; https://doi.org/10.3390/fluids1040038 - 22 Nov 2016
Cited by 12 | Viewed by 4662
Abstract
A thrombus is a blood clot that forms on a surface, and can grow and detach, presenting a high risk for stroke and pulmonary embolism. This risk increases with blood-contacting medical devices, due to the immunological response to foreign surfaces and altered flow [...] Read more.
A thrombus is a blood clot that forms on a surface, and can grow and detach, presenting a high risk for stroke and pulmonary embolism. This risk increases with blood-contacting medical devices, due to the immunological response to foreign surfaces and altered flow patterns that activate the blood and promote thromboembolism (TE). Abnormal blood transport, including vortex behavior and regional stasis, can be assessed from Lagrangian Coherent Structures (LCS). LCS are flow structures that bound transport within a flow field and divide the flow into regions with maximally attracting/repelling surfaces that maximize local shear. LCS can be identified from finite time Lyapunov exponent (FTLE) fields, which are computed from velocity field data. In this study, the goal was to use FTLE analysis to evaluate LCS in the left ventricle (LV) using velocity data obtained from flow visualization of a mock circulatory loop. A model of dilated cardiomyopathy (DCM) was used to investigate the effect of left ventricular assist device (LVAD) support on diastolic filling and transport in the LV. A small thrombus in the left ventricular outflow tract was also considered using data from a corresponding LV model. The DCM LV exhibited a direct flow of 0.8 L/cardiac cycle, which was tripled during LVAD support Delayed ejection flow was doubled, further illustrating the impact of LVAD support on blood transport. An examination of the attracting LCS ridges during diastolic filling showed that the increase is due primarily to augmentation of A wave inflow, which is associated with increased vortex circulation, kinetic energy and Forward FTLE. The introduction of a small thrombus in the left ventricular outflow tract (LVOT) of the LV had a minimal effect on diastolic inflow, but obstructed systolic outflow leading to decreased transport compared with the unobstructed LVOT geometry. Localized FTLE in the LVOT increased dramatically with the small thrombus model, which reflects greater recirculation distal to the thrombus location. The combination of the thrombus and the LVAD increased stasis distal to the thrombus, increasing the likelihood of recurring coagulation during Series flow conditions. The extension of the results of the previous studies with this analysis provides a more sensitive indicator of TE risk than the Eulerian velocity values do, and may provide an important tool for evaluating medical device design, surgical implantation, and treatment options. Full article
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