|
|
| (One intermediate revision by one other user not shown) |
| Line 1: |
Line 1: |
| '''Thermophoresis''', or '''thermodiffusion''',or the '''Soret effect''', or the '''Ludwig-Soret effect''' is a phenomenon observed in mixtures of mobile particles where the different particle types exhibit different responses to the force of a [[temperature gradient]]. The term ''thermophoresis'' most often applies to [[aerosol]] mixtures, but may also commonly refer to the phenomenon in all [[Phase (matter)|phases of matter]]. The term ''Soret effect'' normally applies to liquid mixtures, which behave according to different, less well-understood mechanisms than gaseous mixtures.
| | The author's name is Christy. What me and my family members love is to climb but I'm thinking on starting some thing new. I've usually cherished residing in Alaska. Since he was 18 he's been operating as an info officer but he plans on changing it.<br><br>My homepage ... psychic chat online ([http://kard.dk/?p=24252 click through the next article]) |
| | |
| ==Thermophoretic force==
| |
| The phenomenon is observed at the scale of one millimeter or less. An example that may be observed by the naked eye with good lighting is when the hot rod of an electric heater is surrounded by tobacco smoke: the smoke goes away from the immediate vicinity of the hot rod. As the small particles of air nearest the hot rod are heated, they create a fast flow away from the rod, down the temperature gradient. They have acquired higher kinetic energy with their higher temperature. When they collide with the large, slower-moving particles of the tobacco smoke they push the latter away from the rod. The force that has pushed the smoke particles away from the rod is an example of a thermophoretic force. For illustration see [http://aerosols.wustl.edu/Education/Thermophoresis/section01.html aerosols.wustl.edu].
| |
| | |
| Thermodiffusion is labeled "positive" when particles move from a hot to cold region and "negative" when the reverse is true. Typically the heavier/larger species in a mixture exhibits positive thermophoretic behavior while the lighter/smaller species exhibit negative behavior. In addition to the sizes of the various types of particles and the steepness of the temperature gradient, the heat conductivity and heat absorption of the particles play a role. Recently, Braun and coworkers have suggested that the charge and entropy of the hydration shell of molecules play a major role for the thermophoresis of [[biomolecule]]s in aqueous solutions.<ref name=Duhr1>{{cite journal | author = Duhr S, Braun D | title = Why molecules move along a temperature gradient | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 103 | issue = 52 | pages = 19678–82 |date=December 2006 | pmid = 17164337 | pmc = 1750914 | doi = 10.1073/pnas.0603873103 | url = |bibcode = 2006PNAS..10319678D }}</ref><ref name=Reineck>{{cite journal | author = Reineck P, Wienken CJ, Braun D | title = Thermophoresis of single stranded DNA | journal = Electrophoresis | volume = 31 | issue = 2 | pages = 279–86 |date=January 2010 | pmid = 20084627 | doi = 10.1002/elps.200900505 | url = }}</ref>
| |
| | |
| The quantitative description is given by:
| |
| :<math>\frac{\partial \chi}{\partial t}=\nabla\cdot( D\,\nabla \chi+ D_{T}\, \chi(1-\chi)\,\nabla T)</math>
| |
| | |
| <math>D</math> diffusion coefficient and <math>D_T</math> the thermodiffusion coefficient. The quotient of both coefficients
| |
| | |
| :<math>S_T=\frac{D_T}{D}</math>
| |
| | |
| is called Soret coefficient.
| |
| | |
| The thermophoresis factor has been calculated from molecular interaction potentials derived from known molecular models <ref>[[J. Chem. Phys.]], 50, 4886, (1960)</ref>
| |
| | |
| ==Applications==
| |
| | |
| The thermophoretic force has a number of practical applications. The basis for applications is that, because different particle types move differently under the force of the temperature gradient, the particle types can be separated by that force after they've been mixed together, or prevented from mixing if they're already separated.
| |
| | |
| Impurity ions may move from the cold side of a [[wafer (electronics)|semiconductor wafer]] towards the hot side, since the higher temperature makes the [[transition state|transition]] structure required for atomic jumps more achievable. The diffusive flux may occur in either direction (either up or down the temperature gradient), dependent on the materials involved. Thermophoretic force has been used in commercial precipitators for applications similar to [[electrostatic precipitators]]. It is exploited in the manufacturing of optical fiber in [[vapor deposition]]{{dn|date=February 2012}} processes. It can be important as a transport mechanism in [[fouling]]. Thermophoresis has also been shown to have potential in facilitating [[drug discovery]] by allowing the detection of [[aptamer]] binding by comparison of the bound versus unbound motion of the target molecule.<ref>{{cite journal | author = Baaske P, Wienken CJ, Reineck P, Duhr S, Braun D| title = Optical Thermophoresis for Quantifying the Buffer Dependence of Aptamer Binding | journal = Angewandte Chemie International Edition | volume = 49| issue = 12| pages = 2238–41|date=February 2010 | doi = 10.1002/anie.200903998 | laysummary = http://www.physorg.com/news186225693.html | laysource = Phsyorg.com | pmid = 20186894 }}</ref> This approach has been termed [[Microscale Thermophoresis|microscale thermophoresis]].<ref name=Wienken>{{cite journal | author=Wienken CJ et al. | title=Protein-binding assays in biological liquids using microscale thermophoresis | journal=Nature Communications | year=2010 | volume=1 | doi = 10.1038/ncomms1093|bibcode = 2010NatCo...1E.100W | issue=7 | url=http://www.nature.com/ncomms/journal/v1/n7/full/ncomms1093.html | pages=100 | pmid=20981028}}</ref><ref>An illustration of a device based on microscale thermophoresis at [http://pbaaske.alfahosting.org/typo3/fileadmin/PDFs/Microscale_Thermophoresis.pdf NanoTemper.de]</ref> Furthermore, thermophoresis has been demonstrated as a versatile technique for manipulating single biological macromolecules, such as genomic-length [[DNA]], in micro- and nanochannels by means of light-induced local heating.<ref>{{cite journal | author = Thamdrup LH, Larsen NB, Kristensen A| title = Light-Induced Local Heating for Thermophoretic Manipulation of DNA in Polymer Micro- and Nanochannels| journal = Nano Letters | volume = 10| issue = 3| pages = 826–832|date=February 2010 | doi = 10.1021/nl903190q | laysummary = http://pubs.acs.org/doi/abs/10.1021/nl903190q | laysource = Phsyorg.com | pmid = 20166745 |bibcode = 2010NanoL..10..826T }}</ref> Thermophoresis is one of the methods used to separate different polymer particles in [[field flow fractionation]].<ref>An illustration of a Thermal Field Flow Fractionation Machine based on thermophoresis used to separate mixed polymers at [http://www.postnova.com/thermal-fff.html Postnova.com]</ref>
| |
| | |
| ==History==
| |
| Thermophoresis in gas mixtures was first observed and reported by [[John Tyndall]] in 1870 and further understood by [[John Strutt, 3rd Baron Rayleigh|John Strutt]] (Baron Rayleigh) in 1882.<ref>A brief history of thermophoresis studies is in [http://books.google.co.uk/books?id=O3PQ2BVD8QsC ''Encyclopedia of Surface And Colloid Science'', Volume 2], published by Taylor & Francis, year 2006. John Tyndall's original
| |
| article in year 1870 is online at [http://archive.org/details/scientificaddre01tyndgoog/ Archive.org].</ref> Thermophoresis in liquid mixtures was first observed and reported by [[Carl Ludwig]] in 1856 and further understood by [[Charles Soret]] in 1879. | |
| | |
| [[James Clerk Maxwell]] wrote in 1873 concerning mixtures of different types of molecules (and this could include small [[Aerosol|particulates]] larger than molecules):
| |
| :"This process of diffusion... goes on in gases and liquids and even in some solids.... The dynamical theory also tells us what will happen if molecules of different masses are allowed to knock about together. The greater masses will go slower than the smaller ones, so that, on an average, every molecule, great or small, will have the same energy of motion. The proof of this dynamical theorem, in which I claim the priority, has recently been greatly developed and improved by Dr. Ludwig Boltzmann."<ref>"Molecules" by James Clerk Maxwell, published in September 1873 in [[Nature (magazine)|''Nature'' (magazine)]]. Reproduced online at [http://victorianweb.org/science/maxwell/molecules.html Victorianweb.org].</ref>
| |
| | |
| It has been analyzed theoretically by [[Sydney Chapman (mathematician)|Sydney Chapman]].
| |
| | |
| ==See also==
| |
| * [[Microscale Thermophoresis]]
| |
| * [[Deposition (Aerosol physics)]]
| |
| * [[Dufour effect]]
| |
| * [[Maxwell Stefan diffusion]]
| |
| | |
| ==References==
| |
| {{reflist}}
| |
| | |
| ==External links==
| |
| * A short introduction to thermophoresis, including helpful animated graphics, is at [http://aerosols.wustl.edu/Education/Thermophoresis/section01.html aerosols.wustl.edu]
| |
| *{{YouTube|id=lCB1eCTcCbo|title=Thermophoresis of DNA in an aqueous solution}}
| |
| * [http://scitation.aip.org/content/aip/journal/jcp/32/6/10.1063/1.1731009 ternary mixtures]
| |
| [[Category:Non-equilibrium thermodynamics]]
| |
| [[Category:Aerosols]]
| |
The author's name is Christy. What me and my family members love is to climb but I'm thinking on starting some thing new. I've usually cherished residing in Alaska. Since he was 18 he's been operating as an info officer but he plans on changing it.
My homepage ... psychic chat online (click through the next article)