Optical tweezers - Sideversjonshistorikk

Magnugje: /* Measuring kinetics of folding */

2009-03-17T21:49:45Z

Measuring kinetics of folding

← Eldre sideversjon		Sideversjonen fra 17. mar. 2009 kl. 21:49
Linje 137:		Linje 137:
	[[Image:rna_folding_probability_fit.jpg\|thumb\|250px\|right\|'''Fraction of time spent in the unfolded state vs. applied force''' with probability density function. <math>F_{1/2}</math> refers to the force at which the RNA strand is in the folded and unfolded states for an equal amount of time.<ref name="liphardt" />]]		[[Image:rna_folding_probability_fit.jpg\|thumb\|250px\|right\|'''Fraction of time spent in the unfolded state vs. applied force''' with probability density function. <math>F_{1/2}</math> refers to the force at which the RNA strand is in the folded and unfolded states for an equal amount of time.<ref name="liphardt" />]]

	By attaching a folded molecule of DNA or RNA molecule to a handle, the biopolymer can be unfolded through application of a mechanical force in an optical tweeer setup. Liphardt, Onoa, Smith, Tinoco and Bustamante, unfolded RNA molecules in this way 2001. They applied a gradually increasing force to the strand and found that at a certain force <math>f = 14.5</math>pN, there was a clearly defined discontinuity in the force vs. extension curve. They concluded that this was due to the sudden unfolding of the strand. Also, holding the force constant and not too far from <math>f = 14.5</math>pN, the strand would make sudden jumps back and forth between the folded and the unfolded state and spend a certain total and force dependent time in each state. Subsequently, they made recordings of strand length <math>z</math> vs. time for different applied forces. A force vs. fraction of time spent in the folded state plot was also made. See ~~Figure~~ "Strand length vs. time" and "Fraction of time spent in the unfolded state vs. applied force".<ref name="liphardt">Liphardt, J. et al. (2001). Reversible Unfolding of Single RNA Molecules by Mechanical Force. Science, 292(5517), 733-737.</ref> To this, a force dependent probability density function for the fraction of time spent in the unfolded state could be fitted. The form of the density function is given below.<ref>Nelson, P. (2008). Biological Physics. New York: W. H. Freeman and Comany.</ref>		By attaching a folded molecule of DNA or RNA molecule to a handle, the biopolymer can be unfolded through application of a mechanical force in an optical tweeer setup. Liphardt, Onoa, Smith, Tinoco and Bustamante, unfolded RNA molecules in this way 2001. They applied a gradually increasing force to the strand and found that at a certain force <math>f = 14.5</math>pN, there was a clearly defined discontinuity in the force vs. extension curve. They concluded that this was due to the sudden unfolding of the strand. Also, holding the force constant and not too far from <math>f = 14.5</math>pN, the strand would make sudden jumps back and forth between the folded and the unfolded state and spend a certain total and force dependent time in each state. Subsequently, they made recordings of strand length <math>z</math> vs. time for different applied forces. A force vs. fraction of time spent in the folded state plot was also made. See Figures "Strand length vs. time" and "Fraction of time spent in the unfolded state vs. applied force".<ref name="liphardt">Liphardt, J. et al. (2001). Reversible Unfolding of Single RNA Molecules by Mechanical Force. Science, 292(5517), 733-737.</ref> To this, a force dependent probability density function for the fraction of time spent in the unfolded state could be fitted. The form of the density function is given below.<ref>Nelson, P. (2008). Biological Physics. New York: W. H. Freeman and Comany.</ref>

	:<math>P(f) = \frac{1}{1 + e^{- (\Delta F_0 - f \Delta z)/k_B T}}</math>		:<math>P(f) = \frac{1}{1 + e^{- (\Delta F_0 - f \Delta z)/k_B T}}</math>

Magnugje: /* Measuring kinetics of folding */

2009-03-17T21:49:03Z

Measuring kinetics of folding

← Eldre sideversjon		Sideversjonen fra 17. mar. 2009 kl. 21:49
Linje 137:		Linje 137:
	[[Image:rna_folding_probability_fit.jpg\|thumb\|250px\|right\|'''Fraction of time spent in the unfolded state vs. applied force''' with probability density function. <math>F_{1/2}</math> refers to the force at which the RNA strand is in the folded and unfolded states for an equal amount of time.<ref name="liphardt" />]]		[[Image:rna_folding_probability_fit.jpg\|thumb\|250px\|right\|'''Fraction of time spent in the unfolded state vs. applied force''' with probability density function. <math>F_{1/2}</math> refers to the force at which the RNA strand is in the folded and unfolded states for an equal amount of time.<ref name="liphardt" />]]

	By attaching a folded molecule of DNA or RNA molecule to a handle, the biopolymer can be unfolded through application of a mechanical force in an optical tweeer setup. Liphardt, Onoa, Smith, Tinoco and Bustamante, unfolded RNA molecules in this way 2001. They applied a gradually increasing force to the strand and found that at a certain force <math>f = 14.5</math>pN, there was a clearly defined discontinuity in the force vs. extension curve. They concluded that this was due to the sudden unfolding of the strand. Also, holding the force constant and not too far from <math>f = 14.5</math>pN, the strand would make sudden jumps back and forth between the folded and the unfolded state and spend a certain total and force dependent time in each state. Subsequently, they made recordings of strand length <math>z</math> vs. time for different applied forces. A force vs. fraction of time spent in the folded state plot was also made. See ~~figures to~~ the ~~right~~.<ref name="liphardt">Liphardt, J. et al. (2001). Reversible Unfolding of Single RNA Molecules by Mechanical Force. Science, 292(5517), 733-737.</ref> To this, a force dependent probability density function for the fraction of time spent in the unfolded state could be fitted. The form of the density function is given below.<ref>Nelson, P. (2008). Biological Physics. New York: W. H. Freeman and Comany.</ref>		By attaching a folded molecule of DNA or RNA molecule to a handle, the biopolymer can be unfolded through application of a mechanical force in an optical tweeer setup. Liphardt, Onoa, Smith, Tinoco and Bustamante, unfolded RNA molecules in this way 2001. They applied a gradually increasing force to the strand and found that at a certain force <math>f = 14.5</math>pN, there was a clearly defined discontinuity in the force vs. extension curve. They concluded that this was due to the sudden unfolding of the strand. Also, holding the force constant and not too far from <math>f = 14.5</math>pN, the strand would make sudden jumps back and forth between the folded and the unfolded state and spend a certain total and force dependent time in each state. Subsequently, they made recordings of strand length <math>z</math> vs. time for different applied forces. A force vs. fraction of time spent in the folded state plot was also made. See Figure "Strand length vs. time" and "Fraction of time spent in the unfolded state vs. applied force".<ref name="liphardt">Liphardt, J. et al. (2001). Reversible Unfolding of Single RNA Molecules by Mechanical Force. Science, 292(5517), 733-737.</ref> To this, a force dependent probability density function for the fraction of time spent in the unfolded state could be fitted. The form of the density function is given below.<ref>Nelson, P. (2008). Biological Physics. New York: W. H. Freeman and Comany.</ref>

	:<math>P(f) = \frac{1}{1 + e^{- (\Delta F_0 - f \Delta z)/k_B T}}</math>		:<math>P(f) = \frac{1}{1 + e^{- (\Delta F_0 - f \Delta z)/k_B T}}</math>

Magnugje: /* Measuring transcription by RNA polymerase and behaviour of biological motors */

2009-03-17T21:47:23Z

Measuring transcription by RNA polymerase and behaviour of biological motors

← Eldre sideversjon		Sideversjonen fra 17. mar. 2009 kl. 21:47
Linje 128:		Linje 128:
	[[Image:dna_transcription.jpg\|thumb\|250px\|right\| '''Measurement on DNA transcription:''' An RNA polymerase enzyme is fixed to a bead that is optically trapped. As the DNA strand is transcribed, the stage moves in order to hold the bead in a fixed position relative to the trap. The movement of the enzyme along the strand can then be found from the movement of the stage.<ref name="neuman" />]]		[[Image:dna_transcription.jpg\|thumb\|250px\|right\| '''Measurement on DNA transcription:''' An RNA polymerase enzyme is fixed to a bead that is optically trapped. As the DNA strand is transcribed, the stage moves in order to hold the bead in a fixed position relative to the trap. The movement of the enzyme along the strand can then be found from the movement of the stage.<ref name="neuman" />]]

	A single RNA polymerase enzyme can be chemically fixed to an optical handle and make a transcript of a DNA molecule attached to a moveable stage, as shown in ~~the figure to the right~~. The bead is held at a constant distance from the focus of the optical trap and is thus able to exert a constant force suspending the DNA strand. As the enzyme transcribes the DNA, it moves along the strand. The stage to which the DNA molecule is fixed is then moved about by piezoelectrics such as to maintain the position of the particle within the trap. From recordings of this movement, the enzyme's movement along the strand can be deduced. Such an experiment was performed by Neuman et al. in 2003. They sought to explain why periods of constant RNA polymerase motion are interrupted by frequent pauses.<ref>Neuman. K. C. et al. (2003). Ubiquitous Transcriptional Pausing Is Independent of RNA Polymerase Backtracking. Cell, 115(4), 437-447.</ref>		A single RNA polymerase enzyme can be chemically fixed to an optical handle and make a transcript of a DNA molecule attached to a moveable stage, as shown in Figure "Measurement on DNA transcription". The bead is held at a constant distance from the focus of the optical trap and is thus able to exert a constant force suspending the DNA strand. As the enzyme transcribes the DNA, it moves along the strand. The stage to which the DNA molecule is fixed is then moved about by piezoelectrics such as to maintain the position of the particle within the trap. From recordings of this movement, the enzyme's movement along the strand can be deduced. Such an experiment was performed by Neuman et al. in 2003. They sought to explain why periods of constant RNA polymerase motion are interrupted by frequent pauses.<ref>Neuman. K. C. et al. (2003). Ubiquitous Transcriptional Pausing Is Independent of RNA Polymerase Backtracking. Cell, 115(4), 437-447.</ref>

	Using a similar setup, it is achievable to measure the motion of biological motors moving along a strand in general. Information that can be obtained from these kinds of experiments are for example, if the motor moves constantly or in steps, what the size of the steps might be and how much force the motor is able to exert. Also, it is possible to measure if there is any dependence of ATP concentration in solution on this motion and and what this relationship might be.		Using a similar setup, it is achievable to measure the motion of biological motors moving along a strand in general. Information that can be obtained from these kinds of experiments are for example, if the motor moves constantly or in steps, what the size of the steps might be and how much force the motor is able to exert. Also, it is possible to measure if there is any dependence of ATP concentration in solution on this motion and and what this relationship might be.

Magnugje: /* Dynamic position control and optical trap arrays */

2009-03-17T21:44:08Z

Dynamic position control and optical trap arrays

← Eldre sideversjon		Sideversjonen fra 17. mar. 2009 kl. 21:44
Linje 48:		Linje 48:
	A single beam tweezer can be used to trap a single particle near it's focal point. In this subsection, methods by which it is possible to control the relative positions, in three dimensions, of a number of particles through a dynamic array of optical traps are described. The array can be set up in several ways.		A single beam tweezer can be used to trap a single particle near it's focal point. In this subsection, methods by which it is possible to control the relative positions, in three dimensions, of a number of particles through a dynamic array of optical traps are described. The array can be set up in several ways.

	*'''~~Time shared~~ optical tweezers''' use a scanning laser consecutively focusing on each one of several trapping points for a very short period of time. If the beam is scanned over the desired pattern at a frequency greated than that associated with Brownian time scales, the particles within the array will find themselves confined to one of these points even though it is not lit at them continuously. In order to achieve this rapid scanning of the beam, acousto optic deflectors (AODs) or piezoelectric mirrors can be used.<ref name="grier" /><ref name="terray2">Terray, A., Oakey, J. and Marr, D.W.M. Microfluidic control using colloidal devices. Science 296, 1841-1844 (2002)</ref>		*'''Scanning optical tweezers''' use a scanning laser consecutively focusing on each one of several trapping points for a very short period of time. If the beam is scanned over the desired pattern at a frequency greated than that associated with Brownian time scales, the particles within the array will find themselves confined to one of these points even though it is not lit at them continuously. In order to achieve this rapid scanning of the beam, acousto optic deflectors (AODs) or piezoelectric mirrors can be used.<ref name="grier" /><ref name="terray2">Terray, A., Oakey, J. and Marr, D.W.M. Microfluidic control using colloidal devices. Science 296, 1841-1844 (2002)</ref>

	*'''Holographic optical tweezers''' (HOTs) split the single laser beam into several continuously lit and dynamic traps. The traps are discrete light intensity maxima in the focal plane of the setup. In order to create these maxima, the wavefront of a single laser beam is sculpted in the back aperture through a computer generated hologram in a spatial light modulator (SLM). The focal plane represents the reciprocal space with respect to the back focal plane. Thus calculating the holograms necessary to fix and move particles in a desired way, requires knowledge of the inverse Fourier transform of the trap positions. This can be achieved through application computer algorithms such as the iterative Gerchberg-Saxton or the direct binary search algorithm. Hologram calculation can be done in advance or in real-time relative to particle movement execution.<ref name="chapin">Chapin, Stephen C., Germain, Vincent and Dufresne, Eric R. (2006) Automated trapping, assembly and sorting with holographic optical tweezers. Optics express, 14, 26, 13095-13100.</ref><ref name="sinclair">Sinclair, G. et. al. (2004). Interactive Application in holographic optical tweezers og multi-plane Gerchberg-Saxton algorithm for three-dimensional light shaping. Optics Express, 12, 8, 1665-1670.</ref>		*'''Holographic optical tweezers''' (HOTs) split the single laser beam into several continuously lit and dynamic traps. The traps are discrete light intensity maxima in the focal plane of the setup. In order to create these maxima, the wavefront of a single laser beam is sculpted in the back aperture through a computer generated hologram in a spatial light modulator (SLM). The focal plane represents the reciprocal space with respect to the back focal plane. Thus calculating the holograms necessary to fix and move particles in a desired way, requires knowledge of the inverse Fourier transform of the trap positions. This can be achieved through application computer algorithms such as the iterative Gerchberg-Saxton or the direct binary search algorithm. Hologram calculation can be done in advance or in real-time relative to particle movement execution.<ref name="chapin">Chapin, Stephen C., Germain, Vincent and Dufresne, Eric R. (2006) Automated trapping, assembly and sorting with holographic optical tweezers. Optics express, 14, 26, 13095-13100.</ref><ref name="sinclair">Sinclair, G. et. al. (2004). Interactive Application in holographic optical tweezers og multi-plane Gerchberg-Saxton algorithm for three-dimensional light shaping. Optics Express, 12, 8, 1665-1670.</ref>

Magnugje: /* Microparticle and cell sorting */

2009-03-17T21:42:48Z

Microparticle and cell sorting

← Eldre sideversjon		Sideversjonen fra 17. mar. 2009 kl. 21:42
Linje 73:		Linje 73:
	[[Image:cell_sorting.jpg\|right\|thumb\|200px\|'''Microparticle and cell sorting:''' Single cells or particles are aligned to flow along the vertical axis of the setup. Optical reconition in the analysis region determines which particles that are to be directed right or left by the optical swicth.<ref name="wang" />]]		[[Image:cell_sorting.jpg\|right\|thumb\|200px\|'''Microparticle and cell sorting:''' Single cells or particles are aligned to flow along the vertical axis of the setup. Optical reconition in the analysis region determines which particles that are to be directed right or left by the optical swicth.<ref name="wang" />]]

	An example of a setup for microparticle and cell sorting, as used in an experiment by Wang et al, is shown in ~~the~~ Figure Microparticle and cell sorting.<ref name="wang" /> This particular setup applies optical forces along with the laminar flow characteristics of a microfluidic system. A low Reynolds number environment makes fluid flow analogous to a conveyor belt. The role of the optical switch is then simply to direct particles left or right, corresponding to waste and collection respectively, based on the judgement of the optical recognition stage. The switch may be implemented as an optically actuated mechanical one, but it can also be a right increasing light intensity gradient stretching the full width of the channel that is turned on for target cells or particles that are to be part of the collection, as shown in the figure to the right and below. Also, to allow for left or right direction of several particles at once, it is possible to utilise HOTs. It is possible for the optical recognition stage to identify a variety of particle or cell properties. For example, Wang et al. used such a setup to sort cells based on the fluorescence of a protein<ref name="wang">Wang, M. M. et al. (2004). Microfluidic sorting of mammalian cells by optical force switching. Nature Biotechnology, 23, 83-87.</ref> and Chapin et. al. demonstrated how microparticles can be sorted by size.<ref name="chapin" />		An example of a setup for microparticle and cell sorting, as used in an experiment by Wang et al, is shown in Figure "Microparticle and cell sorting".<ref name="wang" /> This particular setup applies optical forces along with the laminar flow characteristics of a microfluidic system. A low Reynolds number environment makes fluid flow analogous to a conveyor belt. The role of the optical switch is then simply to direct particles left or right, corresponding to waste and collection respectively, based on the judgement of the optical recognition stage. The switch may be implemented as an optically actuated mechanical one, but it can also be a right increasing light intensity gradient stretching the full width of the channel that is turned on for target cells or particles that are to be part of the collection, as shown in the figure to the right and below. Also, to allow for left or right direction of several particles at once, it is possible to utilise HOTs. It is possible for the optical recognition stage to identify a variety of particle or cell properties. For example, Wang et al. used such a setup to sort cells based on the fluorescence of a protein<ref name="wang">Wang, M. M. et al. (2004). Microfluidic sorting of mammalian cells by optical force switching. Nature Biotechnology, 23, 83-87.</ref> and Chapin et. al. demonstrated how microparticles can be sorted by size.<ref name="chapin" />

	==== Optical actuation of micromachines====		==== Optical actuation of micromachines====

Magnugje: /* Microparticle and cell sorting */

2009-03-17T21:42:16Z

Microparticle and cell sorting

← Eldre sideversjon		Sideversjonen fra 17. mar. 2009 kl. 21:42
Linje 73:		Linje 73:
	[[Image:cell_sorting.jpg\|right\|thumb\|200px\|'''Microparticle and cell sorting:''' Single cells or particles are aligned to flow along the vertical axis of the setup. Optical reconition in the analysis region determines which particles that are to be directed right or left by the optical swicth.<ref name="wang" />]]		[[Image:cell_sorting.jpg\|right\|thumb\|200px\|'''Microparticle and cell sorting:''' Single cells or particles are aligned to flow along the vertical axis of the setup. Optical reconition in the analysis region determines which particles that are to be directed right or left by the optical swicth.<ref name="wang" />]]

	An example of a setup for microparticle and cell sorting, as used in an experiment by Wang et al, is shown in the ~~figure to the right~~.<ref name="wang" /> This particular setup applies optical forces along with the laminar flow characteristics of a microfluidic system. A low Reynolds number environment makes fluid flow analogous to a conveyor belt. The role of the optical switch is then simply to direct particles left or right, corresponding to waste and collection respectively, based on the judgement of the optical recognition stage. The switch may be implemented as an optically actuated mechanical one, but it can also be a right increasing light intensity gradient stretching the full width of the channel that is turned on for target cells or particles that are to be part of the collection, as shown in the figure to the right and below. Also, to allow for left or right direction of several particles at once, it is possible to utilise HOTs. It is possible for the optical recognition stage to identify a variety of particle or cell properties. For example, Wang et al. used such a setup to sort cells based on the fluorescence of a protein<ref name="wang">Wang, M. M. et al. (2004). Microfluidic sorting of mammalian cells by optical force switching. Nature Biotechnology, 23, 83-87.</ref> and Chapin et. al. demonstrated how microparticles can be sorted by size.<ref name="chapin" />		An example of a setup for microparticle and cell sorting, as used in an experiment by Wang et al, is shown in the Figure Microparticle and cell sorting.<ref name="wang" /> This particular setup applies optical forces along with the laminar flow characteristics of a microfluidic system. A low Reynolds number environment makes fluid flow analogous to a conveyor belt. The role of the optical switch is then simply to direct particles left or right, corresponding to waste and collection respectively, based on the judgement of the optical recognition stage. The switch may be implemented as an optically actuated mechanical one, but it can also be a right increasing light intensity gradient stretching the full width of the channel that is turned on for target cells or particles that are to be part of the collection, as shown in the figure to the right and below. Also, to allow for left or right direction of several particles at once, it is possible to utilise HOTs. It is possible for the optical recognition stage to identify a variety of particle or cell properties. For example, Wang et al. used such a setup to sort cells based on the fluorescence of a protein<ref name="wang">Wang, M. M. et al. (2004). Microfluidic sorting of mammalian cells by optical force switching. Nature Biotechnology, 23, 83-87.</ref> and Chapin et. al. demonstrated how microparticles can be sorted by size.<ref name="chapin" />

	==== Optical actuation of micromachines====		==== Optical actuation of micromachines====

Aursand på 17. mar. 2009 kl. 12:12

2009-03-17T12:12:58Z

← Eldre sideversjon		Sideversjonen fra 17. mar. 2009 kl. 12:12
Linje 1:		Linje 1:
	'''(This page is the product of the literature project in TFY4335.)'''		'''(This page is the product of the literature project in TFY4335.)'''
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	An optical tweezer is a device using a focused laser beam to apply forces to microscopic objects, and this can be used for control and measurements in a large variety of applications. The manipulated objects can range from nanometer scale to micrometer scale, and the forces range from femtonewtons to nanonewtons.<ref name="neuman">Neuman KC, Block SM, "Optical trapping", Review of Scientific Instruments (2004); 75(9): 2787-2809.</ref> Optical trapping of particles as small as 20-30nm has been demonstrated.<ref name="metallicrayleigh">Svoboda, K. and Blocks S.M. Optical trapping of metallic Rayleigh particles. Opt. Lett 19, 930-932 (1994).</ref> This article will both explain the physical principles behind behind the technique, as well as mention several of its applications. Optical tweezers are part of the [[TFY4335 - Bionanovitenskap]] curriculum.		An optical tweezer is a device using a focused laser beam to apply forces to microscopic objects, and this can be used for control and measurements in a large variety of applications. The manipulated objects can range from nanometer scale to micrometer scale, and the forces range from femtonewtons to nanonewtons.<ref name="neuman">Neuman KC, Block SM, "Optical trapping", Review of Scientific Instruments (2004); 75(9): 2787-2809.</ref> Optical trapping of particles as small as 20-30nm has been demonstrated.<ref name="metallicrayleigh">Svoboda, K. and Blocks S.M. Optical trapping of metallic Rayleigh particles. Opt. Lett 19, 930-932 (1994).</ref> This article will both explain the physical principles behind behind the technique, as well as mention several of its applications. Optical tweezers are part of the [[TFY4335 - Bionanovitenskap]] curriculum.

Magnugje: /* Optical actuation of micromachines */

2009-03-16T20:19:18Z

Optical actuation of micromachines

← Eldre sideversjon		Sideversjonen fra 16. mar. 2009 kl. 20:19
Linje 77:		Linje 77:

	==== Optical actuation of micromachines====		==== Optical actuation of micromachines====
	[[Bilde:rotor.jpg\|~~right~~\|thumb\|150px\|'''Microscopic rotor''' which was both created and drived by optical tweezers. '''a)''' Illustration. '''b)''' Image of the rotor tumbling freely in solution. '''c)''' Illustration. '''d)''' Image of a trapped rotor, prevented from movement and rotation. '''e)''' Image of a rotor trapped in focus while being rotated by optical forces<ref name="galajda" />.]]		[[Bilde:rotor.jpg\|left\|thumb\|150px\|'''Microscopic rotor''' which was both created and drived by optical tweezers. '''a)''' Illustration. '''b)''' Image of the rotor tumbling freely in solution. '''c)''' Illustration. '''d)''' Image of a trapped rotor, prevented from movement and rotation. '''e)''' Image of a rotor trapped in focus while being rotated by optical forces<ref name="galajda" />.]]

	Optical tweezers can not only be used for the assembly and fabrication of tiny mechanical devices, but have also shown great promise as actuators for such systems. Because of the high surface area to volume ratio, friction has been a large problem for micromechanical devices, and the need for precise and relatively strong forces are apparent. The optical tweezers can solve the problem of driving the devices by applying precise forces exactly where they are needed, in a very customizable and controllable manner. <ref name="grier" />		Optical tweezers can not only be used for the assembly and fabrication of tiny mechanical devices, but have also shown great promise as actuators for such systems. Because of the high surface area to volume ratio, friction has been a large problem for micromechanical devices, and the need for precise and relatively strong forces are apparent. The optical tweezers can solve the problem of driving the devices by applying precise forces exactly where they are needed, in a very customizable and controllable manner. <ref name="grier" />

Magnugje: /* Microfluidics and Lab-on-a-chip */

2009-03-16T20:18:34Z

Microfluidics and Lab-on-a-chip

← Eldre sideversjon		Sideversjonen fra 16. mar. 2009 kl. 20:18
Linje 92:		Linje 92:
	Still there are many challenges in constructing a small and versatile lab-on-a-chip system. While traditional lithography is very effective for making the simple channels, further miniaturization has been halted by lack of techniques for fabrication of smaller valves, pumps and mixers. Actuation of these devices has also been a challenge, with the need of a quick, flexible and noninvasive solution. Earlier attempts at pumps and valves based on intricate systems of gears and cantilevers have so far failed to be implemented into microfluidics in a practical way. Optical tweezers can potentially solve many of these problems, with its ability to precisely and dynamically control large amounts of microparticles at the same time, and assemble them into needed devices like valves and pumps. Also as discussed earlier, particles or cells running through such a system can be sorted automatically, and the problem of mixing in laminar flow can be solved through microparticles spinning in an optical vortex or by using a microscopic rotor.		Still there are many challenges in constructing a small and versatile lab-on-a-chip system. While traditional lithography is very effective for making the simple channels, further miniaturization has been halted by lack of techniques for fabrication of smaller valves, pumps and mixers. Actuation of these devices has also been a challenge, with the need of a quick, flexible and noninvasive solution. Earlier attempts at pumps and valves based on intricate systems of gears and cantilevers have so far failed to be implemented into microfluidics in a practical way. Optical tweezers can potentially solve many of these problems, with its ability to precisely and dynamically control large amounts of microparticles at the same time, and assemble them into needed devices like valves and pumps. Also as discussed earlier, particles or cells running through such a system can be sorted automatically, and the problem of mixing in laminar flow can be solved through microparticles spinning in an optical vortex or by using a microscopic rotor.
	<p>		<p>
	[[Image:pump.jpg\|~~left~~\|thumb\|281px\|'''Pump in microfluidics:''' Image of microspheres being moved like a 2D analogue of a screw pump by a scanning optical tweezer. The series of images show the tracer particle(1.5µm) being pumped progressively to the left. The spheres making up the pump have a size of 3µm, and the channel is 6µm wide. <ref name="terray2" />]]		[[Image:pump.jpg\|right\|thumb\|281px\|'''Pump in microfluidics:''' Image of microspheres being moved like a 2D analogue of a screw pump by a scanning optical tweezer. The series of images show the tracer particle(1.5µm) being pumped progressively to the left. The spheres making up the pump have a size of 3µm, and the channel is 6µm wide. <ref name="terray2" />]]
	[[Image:pump2.jpg\|left\|thumb\|262px\|'''Pump in microfluidics:''' Image of the "dumbbell" pump in different stages of rotation. The four 3µm microspheres making up the pump are moved independently by a scanning optical tweezer, one pair clockwise and the other pair counter-clockwise. The tracer particle is 1.5µm and the channel is 6µm wide.<ref name="terray2" />]]		[[Image:pump2.jpg\|left\|thumb\|262px\|'''Pump in microfluidics:''' Image of the "dumbbell" pump in different stages of rotation. The four 3µm microspheres making up the pump are moved independently by a scanning optical tweezer, one pair clockwise and the other pair counter-clockwise. The tracer particle is 1.5µm and the channel is 6µm wide.<ref name="terray2" />]]
	[[Image:valves.jpg\|center\|thumb\|280px\|'''Valves in microfluidics:''' Image of the valves made from microspheres attached in a linear shape through photopolymerization. The size of the large sphere is 3µm, and the rest of the valve is around 1.5µm thick. '''a)''' The large sphere is held in place while the passive valve automatically blocks the flow of particles to the right. '''b)''' When the flow goes to the left the passive valve opens up automatically. '''c/d)''' The large sphere is held in place by the wall with a tweezer while the active valve is actuated by the same tweezer to direct the flow of particles up or down.<ref name="terray" />]]		[[Image:valves.jpg\|center\|thumb\|280px\|'''Valves in microfluidics:''' Image of the valves made from microspheres attached in a linear shape through photopolymerization. The size of the large sphere is 3µm, and the rest of the valve is around 1.5µm thick. '''a)''' The large sphere is held in place while the passive valve automatically blocks the flow of particles to the right. '''b)''' When the flow goes to the left the passive valve opens up automatically. '''c/d)''' The large sphere is held in place by the wall with a tweezer while the active valve is actuated by the same tweezer to direct the flow of particles up or down.<ref name="terray" />]]

Magnugje: /* Microfluidics and Lab-on-a-chip */

2009-03-16T20:18:06Z

Microfluidics and Lab-on-a-chip

← Eldre sideversjon		Sideversjonen fra 16. mar. 2009 kl. 20:18
Linje 92:		Linje 92:
	Still there are many challenges in constructing a small and versatile lab-on-a-chip system. While traditional lithography is very effective for making the simple channels, further miniaturization has been halted by lack of techniques for fabrication of smaller valves, pumps and mixers. Actuation of these devices has also been a challenge, with the need of a quick, flexible and noninvasive solution. Earlier attempts at pumps and valves based on intricate systems of gears and cantilevers have so far failed to be implemented into microfluidics in a practical way. Optical tweezers can potentially solve many of these problems, with its ability to precisely and dynamically control large amounts of microparticles at the same time, and assemble them into needed devices like valves and pumps. Also as discussed earlier, particles or cells running through such a system can be sorted automatically, and the problem of mixing in laminar flow can be solved through microparticles spinning in an optical vortex or by using a microscopic rotor.		Still there are many challenges in constructing a small and versatile lab-on-a-chip system. While traditional lithography is very effective for making the simple channels, further miniaturization has been halted by lack of techniques for fabrication of smaller valves, pumps and mixers. Actuation of these devices has also been a challenge, with the need of a quick, flexible and noninvasive solution. Earlier attempts at pumps and valves based on intricate systems of gears and cantilevers have so far failed to be implemented into microfluidics in a practical way. Optical tweezers can potentially solve many of these problems, with its ability to precisely and dynamically control large amounts of microparticles at the same time, and assemble them into needed devices like valves and pumps. Also as discussed earlier, particles or cells running through such a system can be sorted automatically, and the problem of mixing in laminar flow can be solved through microparticles spinning in an optical vortex or by using a microscopic rotor.
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	[[Image:pump.jpg\|~~right~~\|thumb\|281px\|'''Pump in microfluidics:''' Image of microspheres being moved like a 2D analogue of a screw pump by a scanning optical tweezer. The series of images show the tracer particle(1.5µm) being pumped progressively to the left. The spheres making up the pump have a size of 3µm, and the channel is 6µm wide. <ref name="terray2" />]]		[[Image:pump.jpg\|left\|thumb\|281px\|'''Pump in microfluidics:''' Image of microspheres being moved like a 2D analogue of a screw pump by a scanning optical tweezer. The series of images show the tracer particle(1.5µm) being pumped progressively to the left. The spheres making up the pump have a size of 3µm, and the channel is 6µm wide. <ref name="terray2" />]]
	[[Image:pump2.jpg\|left\|thumb\|262px\|'''Pump in microfluidics:''' Image of the "dumbbell" pump in different stages of rotation. The four 3µm microspheres making up the pump are moved independently by a scanning optical tweezer, one pair clockwise and the other pair counter-clockwise. The tracer particle is 1.5µm and the channel is 6µm wide.<ref name="terray2" />]]		[[Image:pump2.jpg\|left\|thumb\|262px\|'''Pump in microfluidics:''' Image of the "dumbbell" pump in different stages of rotation. The four 3µm microspheres making up the pump are moved independently by a scanning optical tweezer, one pair clockwise and the other pair counter-clockwise. The tracer particle is 1.5µm and the channel is 6µm wide.<ref name="terray2" />]]
	[[Image:valves.jpg\|center\|thumb\|280px\|'''Valves in microfluidics:''' Image of the valves made from microspheres attached in a linear shape through photopolymerization. The size of the large sphere is 3µm, and the rest of the valve is around 1.5µm thick. '''a)''' The large sphere is held in place while the passive valve automatically blocks the flow of particles to the right. '''b)''' When the flow goes to the left the passive valve opens up automatically. '''c/d)''' The large sphere is held in place by the wall with a tweezer while the active valve is actuated by the same tweezer to direct the flow of particles up or down.<ref name="terray" />]]		[[Image:valves.jpg\|center\|thumb\|280px\|'''Valves in microfluidics:''' Image of the valves made from microspheres attached in a linear shape through photopolymerization. The size of the large sphere is 3µm, and the rest of the valve is around 1.5µm thick. '''a)''' The large sphere is held in place while the passive valve automatically blocks the flow of particles to the right. '''b)''' When the flow goes to the left the passive valve opens up automatically. '''c/d)''' The large sphere is held in place by the wall with a tweezer while the active valve is actuated by the same tweezer to direct the flow of particles up or down.<ref name="terray" />]]