Articles de revistahttp://hdl.handle.net/2117/32092024-03-28T10:06:53Z2024-03-28T10:06:53ZStudy analysis of thermal, dielectric and functional characteristics of an ethylene polyethylene diene monomer blended with end-of-life tire microparticles amountsMarín Genescà, MarcMujal-Rosas, Ramon MariaGarcia Amoros, JordiMudarra López, MiguelRamis Juan, XavierColom Fajula, Xavierhttp://hdl.handle.net/2117/3499462021-07-25T20:39:30Z2021-07-22T09:25:19ZStudy analysis of thermal, dielectric and functional characteristics of an ethylene polyethylene diene monomer blended with end-of-life tire microparticles amounts
Marín Genescà, Marc; Mujal-Rosas, Ramon Maria; Garcia Amoros, Jordi; Mudarra López, Miguel; Ramis Juan, Xavier; Colom Fajula, Xavier
The recycling and disposal of disused tires is a topic of great concern to today’s companies, researchers, and society in general. In this sense, our research aims to recycle end-of-life tires (GTRs) through the separation of the fraction of vulcanized rubber from the other compounds in order to later grind this fraction and separate it into lower particle sizes. Finally, we aim to incorporate these GTR particles as a filler of an ethylene-polyethylene-diene monomer (EPDM). The obtained composites with EPDM and GTR are tested (5%, 10%, 20%) comparing these values with neat EPDM as a control sample. Thermal tests such as differential calorimetry (DSC) and thermogravimetric analysis (TGA) as well as dielectric tests (DEA) are performed in order to characterize these materials and check their viability as dielectric or semiconductor, for industrial use. It is checked how the presence of GTR increases functional properties such as conductivity/permittivity. The influence of temperature (40 to 120 °C) and addition of GTR particles in electrical properties has also been analyzed. The dielectric behavior of these composites is fully characterized, analyzing the different types of relaxation with increasing frequency (10 mHz to 3 MHz), using the electric modulus, and Argand diagrams among other measures. The influence of GTR and temperature in the dielectric and thermal behavior of these materials has been analyzed, where CB of GTR creates interfacial polarization phenomena in the dielectric behavior of the composite and increases the permittivity (real and imaginary) as well as the conductivity. Finally, with these obtained properties, the possible application of EPDM/GTR composites as industrial dielectrics has been studied
2021-07-22T09:25:19ZMarín Genescà, MarcMujal-Rosas, Ramon MariaGarcia Amoros, JordiMudarra López, MiguelRamis Juan, XavierColom Fajula, XavierThe recycling and disposal of disused tires is a topic of great concern to today’s companies, researchers, and society in general. In this sense, our research aims to recycle end-of-life tires (GTRs) through the separation of the fraction of vulcanized rubber from the other compounds in order to later grind this fraction and separate it into lower particle sizes. Finally, we aim to incorporate these GTR particles as a filler of an ethylene-polyethylene-diene monomer (EPDM). The obtained composites with EPDM and GTR are tested (5%, 10%, 20%) comparing these values with neat EPDM as a control sample. Thermal tests such as differential calorimetry (DSC) and thermogravimetric analysis (TGA) as well as dielectric tests (DEA) are performed in order to characterize these materials and check their viability as dielectric or semiconductor, for industrial use. It is checked how the presence of GTR increases functional properties such as conductivity/permittivity. The influence of temperature (40 to 120 °C) and addition of GTR particles in electrical properties has also been analyzed. The dielectric behavior of these composites is fully characterized, analyzing the different types of relaxation with increasing frequency (10 mHz to 3 MHz), using the electric modulus, and Argand diagrams among other measures. The influence of GTR and temperature in the dielectric and thermal behavior of these materials has been analyzed, where CB of GTR creates interfacial polarization phenomena in the dielectric behavior of the composite and increases the permittivity (real and imaginary) as well as the conductivity. Finally, with these obtained properties, the possible application of EPDM/GTR composites as industrial dielectrics has been studiedComparative study of mechanical and electrical relaxations in poly(etherimide). Part 2Diaz Calleja, RicardoFriederichs, S.Jaímes, C.Sanchis, Jose MariaBelana Punseti, JuanCañadas Lorenzo, Juan CarlosDiego Vives, José AntonioMudarra López, Miguelhttp://hdl.handle.net/2117/3304502021-05-20T16:15:10Z2020-10-19T17:39:49ZComparative study of mechanical and electrical relaxations in poly(etherimide). Part 2
Diaz Calleja, Ricardo; Friederichs, S.; Jaímes, C.; Sanchis, Jose Maria; Belana Punseti, Juan; Cañadas Lorenzo, Juan Carlos; Diego Vives, José Antonio; Mudarra López, Miguel
The curves describing the relaxation behaviour of poly(etherimide) at several frequencies shows in the dielectric lossÈtemperature plot c and b relax- ations centred at [95¡C and 100¡C, respectively, at 10 Hz. The glassÈrubber relaxation or a process appears at 225¡C at 10 Hz; at this temperature free charge conductivity and blocking electrode phenomena become dominant at fre- quencies below 10 Hz. The same three relaxations are observed by dynamic mechanical thermal analysis (DMS). The strength of the c and a relaxations can be estimated from the Ðtting of empirical relaxation functions, such as the FuossÈ Kirkwood and HavriliakÈNegami equations, to the dielectric data measured in the frequency domain. An electric model was used to separate the dipolar response from conductivity contributions in the glassÈrubber relaxation. Finally, the e†ect of water on the low-temperature relaxation has been demonstrated by dielectric and mechanical measurements.
2020-10-19T17:39:49ZDiaz Calleja, RicardoFriederichs, S.Jaímes, C.Sanchis, Jose MariaBelana Punseti, JuanCañadas Lorenzo, Juan CarlosDiego Vives, José AntonioMudarra López, MiguelThe curves describing the relaxation behaviour of poly(etherimide) at several frequencies shows in the dielectric lossÈtemperature plot c and b relax- ations centred at [95¡C and 100¡C, respectively, at 10 Hz. The glassÈrubber relaxation or a process appears at 225¡C at 10 Hz; at this temperature free charge conductivity and blocking electrode phenomena become dominant at fre- quencies below 10 Hz. The same three relaxations are observed by dynamic mechanical thermal analysis (DMS). The strength of the c and a relaxations can be estimated from the Ðtting of empirical relaxation functions, such as the FuossÈ Kirkwood and HavriliakÈNegami equations, to the dielectric data measured in the frequency domain. An electric model was used to separate the dipolar response from conductivity contributions in the glassÈrubber relaxation. Finally, the e†ect of water on the low-temperature relaxation has been demonstrated by dielectric and mechanical measurements.Influence of Polymethylmethacrylate microstructure on its conductive properties at high temperatureGuarrotxena Arlunduaga, Miren NekaneMudarra López, Miguelhttp://hdl.handle.net/2117/1853622020-09-01T00:29:44Z2020-04-28T06:12:06ZInfluence of Polymethylmethacrylate microstructure on its conductive properties at high temperature
Guarrotxena Arlunduaga, Miren Nekane; Mudarra López, Miguel
The influence of a set of tacticity-governed microstructures on the conductive properties of poly(methyl methacrylate) has been studied at high temperatures. Those structures are specially the mmmr and the mmmmrx (x = m or r), which occur when an isotactic sequence breaks-off, and also the rrrm-based termini of syndiotactic sequences. The electrical properties have been studied at the electrical modulus level, assuming a dispersive conductivity to explain conduction processes and Havriliak-Negami equation to evaluate dipolar contribution. A good agreement between experimental data and the model is observed, and some considerations about the conductive processes can be concluded. Conductivity is thermally activated at the temperature range considered, and ac regime can be associated with a correlated ion hopping of carrier process, which does not reacha strongly correlated regime, what we associate with a high relaxation time of carriers at high temperatures that do allow carriers to follow processes associated to a.c. regime.Interestingly, conductivity is shown to be dependent on the mmmrm-based stereosequences longer than one heptad. These stereosequences have been shown to exhibit enhanced free volume and rotational motion, what may explain the conductivity-mmmrm structure correlations as found on this work.
2020-04-28T06:12:06ZGuarrotxena Arlunduaga, Miren NekaneMudarra López, MiguelThe influence of a set of tacticity-governed microstructures on the conductive properties of poly(methyl methacrylate) has been studied at high temperatures. Those structures are specially the mmmr and the mmmmrx (x = m or r), which occur when an isotactic sequence breaks-off, and also the rrrm-based termini of syndiotactic sequences. The electrical properties have been studied at the electrical modulus level, assuming a dispersive conductivity to explain conduction processes and Havriliak-Negami equation to evaluate dipolar contribution. A good agreement between experimental data and the model is observed, and some considerations about the conductive processes can be concluded. Conductivity is thermally activated at the temperature range considered, and ac regime can be associated with a correlated ion hopping of carrier process, which does not reacha strongly correlated regime, what we associate with a high relaxation time of carriers at high temperatures that do allow carriers to follow processes associated to a.c. regime.Interestingly, conductivity is shown to be dependent on the mmmrm-based stereosequences longer than one heptad. These stereosequences have been shown to exhibit enhanced free volume and rotational motion, what may explain the conductivity-mmmrm structure correlations as found on this work.Effects of UV radiation on the charge trapping capability of PETCañadas Lorenzo, Juan CarlosDiego Vives, José AntonioMudarra López, MiguelParsa, Seyedeh ElahehSellarès González, Jordihttp://hdl.handle.net/2117/1308182022-11-20T08:33:58Z2019-03-25T14:41:43ZEffects of UV radiation on the charge trapping capability of PET
Cañadas Lorenzo, Juan Carlos; Diego Vives, José Antonio; Mudarra López, Miguel; Parsa, Seyedeh Elaheh; Sellarès González, Jordi
Poly(ethylene terephthalate) (PET) is able to retain space charge in traps, as is usual in dielectric materials. This allows the material to attain an almost permanent polarization when space charge is displaced by an external electric field or is injected from an electrode. We have studied the influence of UV irradiation on the charge trapping capability of PET in samples exposed for different periods of time, up to 10 weeks. The pulsed electro-acoustic technique (PEA) has been used to determine the charge profile. The injected charge that the material is able to retain on the irradiated surface increases with irradiation time. This indicates the formation of new traps. An extensive characterization of these localized states has been performed by the technique of thermally stimulated depolarization currents. Parameters of charge relaxation kinetics have been obtained by fitting spectra of the space charge relaxation current of a semicrystalline polymeric material peak (), related to injected charge, to the general-order kinetics model. A relaxation map analysis shows that relaxation times become more distributed and the activation energy decreases as irradiation time is increased. The activation energy decreases by approximately 10% after 10 weeks of exposure. These results show that UV irradiation creates additional traps on the treated surface, which agrees with PEA results, and that the energy depth of these traps is shallower and it is more distributed than in the case of pre-existing traps.
2019-03-25T14:41:43ZCañadas Lorenzo, Juan CarlosDiego Vives, José AntonioMudarra López, MiguelParsa, Seyedeh ElahehSellarès González, JordiPoly(ethylene terephthalate) (PET) is able to retain space charge in traps, as is usual in dielectric materials. This allows the material to attain an almost permanent polarization when space charge is displaced by an external electric field or is injected from an electrode. We have studied the influence of UV irradiation on the charge trapping capability of PET in samples exposed for different periods of time, up to 10 weeks. The pulsed electro-acoustic technique (PEA) has been used to determine the charge profile. The injected charge that the material is able to retain on the irradiated surface increases with irradiation time. This indicates the formation of new traps. An extensive characterization of these localized states has been performed by the technique of thermally stimulated depolarization currents. Parameters of charge relaxation kinetics have been obtained by fitting spectra of the space charge relaxation current of a semicrystalline polymeric material peak (), related to injected charge, to the general-order kinetics model. A relaxation map analysis shows that relaxation times become more distributed and the activation energy decreases as irradiation time is increased. The activation energy decreases by approximately 10% after 10 weeks of exposure. These results show that UV irradiation creates additional traps on the treated surface, which agrees with PEA results, and that the energy depth of these traps is shallower and it is more distributed than in the case of pre-existing traps.Influence of internal flexibility on the double glass transition in a series of odd non-symmetric liquid crystal dimers characterised by dielectric measurementsDiego Vives, José AntonioSellarès González, JordiDíez Berart, SergioSalud Puig, JosepCañadas Lorenzo, Juan CarlosMudarra López, MiguelLópez Pérez, David Orenciode la Fuente Lavin, Maria RosarioRos, M Blancahttp://hdl.handle.net/2117/1064222020-07-23T21:38:50Z2017-07-14T09:36:40ZInfluence of internal flexibility on the double glass transition in a series of odd non-symmetric liquid crystal dimers characterised by dielectric measurements
Diego Vives, José Antonio; Sellarès González, Jordi; Díez Berart, Sergio; Salud Puig, Josep; Cañadas Lorenzo, Juan Carlos; Mudarra López, Miguel; López Pérez, David Orencio; de la Fuente Lavin, Maria Rosario; Ros, M Blanca
Dielectric measurements (thermally stimulated depolarisation currents and broadband dielectric spectroscopy) have been performed near the glass transition to study the glass transition on the odd non-symmetric liquid crystal (LC) dimers of the series -(4-cyanobiphenyl-4'-oxy)--(1-pyreniminebenzylidene-4'-oxy) alkanes (CBOnO.Py) with n ranging from 3 to 9. A previous study [S. Diez-Berart et al., Materials 8 (2015) 3334] carried out in CBO11O.Py showed the presence of two glass transition temperatures, attributed to different molecular motions of the terminal groups. The study performed allows us to analyse the molecular dynamics in the rest of the series and determine the role played by the flexible spacer. Parallel and perpendicular orientations of the molecular director with regards to the probe electric field have been investigated. The low and intermediate observed relaxations are explained in the framework of Stocchero's theoretical model [M. Stocchero, J. Chem. Phys. 121 (2004) 8079] for the dielectric behaviour of non-symmetric LCs dimers, as independent end-over-end rotations of each terminal semi-rigid unit. As the length of the spacer chain in the series of compounds decreases, the different relaxations become progressively more coupled at the glass transition. Numerical simulations of the calorimetric response from the obtained kinetic parameters show good agreement with experimental behaviour.
2017-07-14T09:36:40ZDiego Vives, José AntonioSellarès González, JordiDíez Berart, SergioSalud Puig, JosepCañadas Lorenzo, Juan CarlosMudarra López, MiguelLópez Pérez, David Orenciode la Fuente Lavin, Maria RosarioRos, M BlancaDielectric measurements (thermally stimulated depolarisation currents and broadband dielectric spectroscopy) have been performed near the glass transition to study the glass transition on the odd non-symmetric liquid crystal (LC) dimers of the series -(4-cyanobiphenyl-4'-oxy)--(1-pyreniminebenzylidene-4'-oxy) alkanes (CBOnO.Py) with n ranging from 3 to 9. A previous study [S. Diez-Berart et al., Materials 8 (2015) 3334] carried out in CBO11O.Py showed the presence of two glass transition temperatures, attributed to different molecular motions of the terminal groups. The study performed allows us to analyse the molecular dynamics in the rest of the series and determine the role played by the flexible spacer. Parallel and perpendicular orientations of the molecular director with regards to the probe electric field have been investigated. The low and intermediate observed relaxations are explained in the framework of Stocchero's theoretical model [M. Stocchero, J. Chem. Phys. 121 (2004) 8079] for the dielectric behaviour of non-symmetric LCs dimers, as independent end-over-end rotations of each terminal semi-rigid unit. As the length of the spacer chain in the series of compounds decreases, the different relaxations become progressively more coupled at the glass transition. Numerical simulations of the calorimetric response from the obtained kinetic parameters show good agreement with experimental behaviour.A new approach to design an efficient micropost array for enhanced direct-current insulator-based dielectrophoretic trappingMohammadi, MahdiJavad Zare, MohammadMadadi, HojjatSellarès González, JordiCasals Terré, Jasminahttp://hdl.handle.net/2117/1023662020-07-23T22:29:45Z2017-03-13T10:01:04ZA new approach to design an efficient micropost array for enhanced direct-current insulator-based dielectrophoretic trapping
Mohammadi, Mahdi; Javad Zare, Mohammad; Madadi, Hojjat; Sellarès González, Jordi; Casals Terré, Jasmina
Direct-current insulator-based dielectrophoresis (DC-iDEP) is a well-known technique that benefits from the electric field gradients generated by an array of insulating posts to separate or trap biological particles. The aim of this study is to provide a first geometrical relationship of the post array that independent of the particles and/or medium, maximizes the trapping. A novel figure of merit is proposed to maximize the particle trapping in the post array while minimizing the required voltage, with a similar footprint and channel thickness. Different post array models with the variation of transversal distance (10 to 60 µm), longitudinal distance (10 to 80 µm), and post radius (10 to 150 µm) were analyzed using COMSOL Multiphysics finite element software. The obtained results indicated that a post radius of 40 µm larger than the transversal distance between posts could enhance the trapping condition between 56 % (for a transversal distance of 10 µm) and 341 % (for a transversal distance of 60 µm). For the validation of the numerical results, several microchannels with embedded post arrays were manufactured in polydimethylsiloxane (PDMS) and the particle trapping patterns of 6-µm-diameter polystyrene particles were measured experimentally. The experiments confirm the same trends as pointed out by the numerical analysis. The results show that this new figure of merit and geometrical relationship can be used to reduce the required electric field to achieve effective particle trapping and, therefore, avoid the negative effects of Joule heating in cells or viable particles. The main advantage of these results is that they depend only on the geometry of the micropost array and are valid for trapping different particles suspended in different media.
This is a copy of the author 's final draft version of an article published in the journal Analytical and bioanalytical chemistry. The final publication is available at Springer via http://dx.doi.org/10.1007/s00216-016-9629-2
2017-03-13T10:01:04ZMohammadi, MahdiJavad Zare, MohammadMadadi, HojjatSellarès González, JordiCasals Terré, JasminaDirect-current insulator-based dielectrophoresis (DC-iDEP) is a well-known technique that benefits from the electric field gradients generated by an array of insulating posts to separate or trap biological particles. The aim of this study is to provide a first geometrical relationship of the post array that independent of the particles and/or medium, maximizes the trapping. A novel figure of merit is proposed to maximize the particle trapping in the post array while minimizing the required voltage, with a similar footprint and channel thickness. Different post array models with the variation of transversal distance (10 to 60 µm), longitudinal distance (10 to 80 µm), and post radius (10 to 150 µm) were analyzed using COMSOL Multiphysics finite element software. The obtained results indicated that a post radius of 40 µm larger than the transversal distance between posts could enhance the trapping condition between 56 % (for a transversal distance of 10 µm) and 341 % (for a transversal distance of 60 µm). For the validation of the numerical results, several microchannels with embedded post arrays were manufactured in polydimethylsiloxane (PDMS) and the particle trapping patterns of 6-µm-diameter polystyrene particles were measured experimentally. The experiments confirm the same trends as pointed out by the numerical analysis. The results show that this new figure of merit and geometrical relationship can be used to reduce the required electric field to achieve effective particle trapping and, therefore, avoid the negative effects of Joule heating in cells or viable particles. The main advantage of these results is that they depend only on the geometry of the micropost array and are valid for trapping different particles suspended in different media.Accreditation of Spanish Engineering Programs, first experiences. The case of the Terrassa School of EngineeringÁlvarez del Castillo, María DoloresMata Pou, MireiaCañavate Ávila, Francisco JavierMarqués Calvo, José JoaquínEspot Piñol, CarmenForcada Plaza, SantiagoVoltas Aguilar, JordiGarrido Soriano, NúriaSellarès González, JordiGil Bonet, Alfredhttp://hdl.handle.net/2117/850362024-02-11T09:56:49Z2016-04-01T07:59:03ZAccreditation of Spanish Engineering Programs, first experiences. The case of the Terrassa School of Engineering
Álvarez del Castillo, María Dolores; Mata Pou, Mireia; Cañavate Ávila, Francisco Javier; Marqués Calvo, José Joaquín; Espot Piñol, Carmen; Forcada Plaza, Santiago; Voltas Aguilar, Jordi; Garrido Soriano, Núria; Sellarès González, Jordi; Gil Bonet, Alfred
The implementation of the European Space for Higher Education has entailed new requirements for Spanish Higher Education Programs. Regulations (RD 1393, 2007) stablish that university programs, in order to have official validity, must be submitted to an external evaluation process before their official implementation, denominated Validation, and to an ex-post process or Accreditation. Terrassa School of Engineering (EET) was one of the first schools in Spain to adapt to the European Space for Higher Education, in the academic period 2009-10 and then, one of the first university institutions submitted to an accreditation process. In this communication, the important role of the Internal Quality Assurance System in the assessment of the school’s programs is exposed as well as the approach followed in the key steps of the process: Accreditation
2016-04-01T07:59:03ZÁlvarez del Castillo, María DoloresMata Pou, MireiaCañavate Ávila, Francisco JavierMarqués Calvo, José JoaquínEspot Piñol, CarmenForcada Plaza, SantiagoVoltas Aguilar, JordiGarrido Soriano, NúriaSellarès González, JordiGil Bonet, AlfredThe implementation of the European Space for Higher Education has entailed new requirements for Spanish Higher Education Programs. Regulations (RD 1393, 2007) stablish that university programs, in order to have official validity, must be submitted to an external evaluation process before their official implementation, denominated Validation, and to an ex-post process or Accreditation. Terrassa School of Engineering (EET) was one of the first schools in Spain to adapt to the European Space for Higher Education, in the academic period 2009-10 and then, one of the first university institutions submitted to an accreditation process. In this communication, the important role of the Internal Quality Assurance System in the assessment of the school’s programs is exposed as well as the approach followed in the key steps of the process: AccreditationSublinear dispersive conductivity in polyetherimides by the electric modulus formalismMudarra López, MiguelSellarès González, JordiCañadas Lorenzo, Juan CarlosDiego Vives, José Antoniohttp://hdl.handle.net/2117/847342020-07-23T20:12:39Z2016-03-18T16:18:30ZSublinear dispersive conductivity in polyetherimides by the electric modulus formalism
Mudarra López, Miguel; Sellarès González, Jordi; Cañadas Lorenzo, Juan Carlos; Diego Vives, José Antonio
Two commercially available polyetherimides, Ultem 1000 and Ultem 5000, have been studied by means of Dynamic Electrical Analysis. Results show that at temperatures above the glass transition dielectric response is highly influenced by space charge. Obtained data is analyzed using the electric modulus formalism. The real part of the conductivity is conveniently described by a sublinear power law dependency (¿n with n<;1), as Argand plots reveal, associated with correlated hopping of carriers. The imaginary part of the electric modulus shows a peak at low frequencies related to conduction processes. The modelisation of this peak allows us to obtain the dependence of the conductivity (s0), the fractional exponent (n) and the crossover frequency (¿p) on the temperature, among other parameters. The a relaxation, which appears at higher frequencies, has also to be modeled since it overlaps the conductivity relaxation. The study of the parameters in terms of the temperature allows us to identify the ones that are thermally activated. The difference between the conductivity relaxation time and the Maxwell relaxation time indicates the presence of deep traps. The coupling model points out that the correlation of the ionic motion diminishes with temperature, probably due to increasing disorder associated with thermal agitation.
(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or
lists, or reuse of any copyrighted components of this work in other works.
2016-03-18T16:18:30ZMudarra López, MiguelSellarès González, JordiCañadas Lorenzo, Juan CarlosDiego Vives, José AntonioTwo commercially available polyetherimides, Ultem 1000 and Ultem 5000, have been studied by means of Dynamic Electrical Analysis. Results show that at temperatures above the glass transition dielectric response is highly influenced by space charge. Obtained data is analyzed using the electric modulus formalism. The real part of the conductivity is conveniently described by a sublinear power law dependency (¿n with n<;1), as Argand plots reveal, associated with correlated hopping of carriers. The imaginary part of the electric modulus shows a peak at low frequencies related to conduction processes. The modelisation of this peak allows us to obtain the dependence of the conductivity (s0), the fractional exponent (n) and the crossover frequency (¿p) on the temperature, among other parameters. The a relaxation, which appears at higher frequencies, has also to be modeled since it overlaps the conductivity relaxation. The study of the parameters in terms of the temperature allows us to identify the ones that are thermally activated. The difference between the conductivity relaxation time and the Maxwell relaxation time indicates the presence of deep traps. The coupling model points out that the correlation of the ionic motion diminishes with temperature, probably due to increasing disorder associated with thermal agitation.Hydrodynamic and direct-current insulator-based dielectrophoresis (H-DC-iDEP) microfluidic blood plasma separationMohammadi, MahdiMadadi, HojjatCasals Terré, JasminaSellarès González, Jordihttp://hdl.handle.net/2117/813482022-05-17T10:38:17Z2016-01-13T12:18:35ZHydrodynamic and direct-current insulator-based dielectrophoresis (H-DC-iDEP) microfluidic blood plasma separation
Mohammadi, Mahdi; Madadi, Hojjat; Casals Terré, Jasmina; Sellarès González, Jordi
Evaluation and diagnosis of blood alterations is a common request for clinical laboratories, requiring a complex technological approach and dedication of health resources. In this paper, we present a microfluidic device that owing to a novel combination of hydrodynamic and dielectrophoretic techniques can separate plasma from fresh blood in a microfluidic channel and for the first time allows optical real-time monitoring of the components of plasma without pre- or post-processing. The microchannel is based on a set of dead-end branches at each side and is initially filled using capillary forces with a 2-mu L droplet of fresh blood. During this process, stagnation zones are generated at the dead-end branches and some red blood cells (RBCs) are trapped there. An electric field is then applied and dielectrophoretic trapping of RBCs is used to prevent more RBCs entering into the channel, which works like a sieve. Besides, an electroosmotic flow is generated to sweep the rest of the RBCs from the central part of the channel. Consequently, an RBC-free zone of plasma is formed in the middle of the channel, allowing real-time monitoring of the platelet behavior. To study the generation of stagnation zones and to ensure RBC trapping in the initial constrictions, two numerical models were solved. The proposed experimental design separates up to 0.1 mu L blood plasma from a 2-mu L fresh human blood droplet. In this study, a plasma purity of 99 % was achieved after 7 min, according to the measurements taken by image analysis.
2016-01-13T12:18:35ZMohammadi, MahdiMadadi, HojjatCasals Terré, JasminaSellarès González, JordiEvaluation and diagnosis of blood alterations is a common request for clinical laboratories, requiring a complex technological approach and dedication of health resources. In this paper, we present a microfluidic device that owing to a novel combination of hydrodynamic and dielectrophoretic techniques can separate plasma from fresh blood in a microfluidic channel and for the first time allows optical real-time monitoring of the components of plasma without pre- or post-processing. The microchannel is based on a set of dead-end branches at each side and is initially filled using capillary forces with a 2-mu L droplet of fresh blood. During this process, stagnation zones are generated at the dead-end branches and some red blood cells (RBCs) are trapped there. An electric field is then applied and dielectrophoretic trapping of RBCs is used to prevent more RBCs entering into the channel, which works like a sieve. Besides, an electroosmotic flow is generated to sweep the rest of the RBCs from the central part of the channel. Consequently, an RBC-free zone of plasma is formed in the middle of the channel, allowing real-time monitoring of the platelet behavior. To study the generation of stagnation zones and to ensure RBC trapping in the initial constrictions, two numerical models were solved. The proposed experimental design separates up to 0.1 mu L blood plasma from a 2-mu L fresh human blood droplet. In this study, a plasma purity of 99 % was achieved after 7 min, according to the measurements taken by image analysis.Two glass transitions associated to different dynamic disorders in the nematic glassy state of a non-symmetric liquid crystal dimer dopped with gamma-alumina nanoparticlesDíez Berart, SergioLópez Pérez, David OrencioSalud Puig, JosepDiego Vives, José AntonioSellarès González, JordiRobles Hernández, BeatrizDe la Fuente, Maria RosarioBlanca Ros, Maríahttp://hdl.handle.net/2117/767832020-07-23T22:27:48Z2015-09-15T09:23:26ZTwo glass transitions associated to different dynamic disorders in the nematic glassy state of a non-symmetric liquid crystal dimer dopped with gamma-alumina nanoparticles
Díez Berart, Sergio; López Pérez, David Orencio; Salud Puig, Josep; Diego Vives, José Antonio; Sellarès González, Jordi; Robles Hernández, Beatriz; De la Fuente, Maria Rosario; Blanca Ros, María
In the present work, the nematic glassy state of the non-symmetric LC dimer -(4-cyanobiphenyl-4-yloxy)--(1-pyrenimine-benzylidene-4-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of -alumina nanoparticles, in several concentrations.
2015-09-15T09:23:26ZDíez Berart, SergioLópez Pérez, David OrencioSalud Puig, JosepDiego Vives, José AntonioSellarès González, JordiRobles Hernández, BeatrizDe la Fuente, Maria RosarioBlanca Ros, MaríaIn the present work, the nematic glassy state of the non-symmetric LC dimer -(4-cyanobiphenyl-4-yloxy)--(1-pyrenimine-benzylidene-4-oxy) undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of -alumina nanoparticles, in several concentrations.