Optical Tweezer is actually called a "single-beam gradient force trap" or "single-beam gradient force trap" is a scientific instrument that uses a focused laser beam to obtain a strong attractive force or a force rejected (usually in the order of piconewton, 10 ^ {-12}) which depends on the difference in refractive index on the handle physical and dielectric objects microscopic movement. Optical Tweezers have been successful in the investigation of various biological systems in recent years.History and Development
The detection of optical scattering and gradient forces on a micrometer-scale particles were first reported in 1970 by Arthur Ashkin, a scientist who worked at Bell Labs. A year later, Ashkin and colleagues report the first observation on what is now commonly known as an optical trap: a focused beam of light capable of firmly holding microscopic particles stable in three dimensions.
One of the owners of conference papers, 1986, the Secretariat of the United States of energy, Steven Chu, will use the optical trap in his research in cooling and trapping of neutral atoms. From this study, Chu was awarded the Nobel Prize in Physics with Claude Cohen-Tannoudji and William D. Philllips. In an interview, Steven Chu explains how Ashkin first dreamed optical trap as a method for capturing atoms. Ashkin states are able to capture larger particles (diameter 10 to 10,000 nanometers) but it does inspire Chu to extend the technique to capture the neutral atom (diameter 0.1 nanometer) by making use of resonant laser light and magnetic gradient trap.
In the late 1980s, Arthur Ashkin and Joseph M. Dziedzic demonstrated the first application of technology in the biological sciences, by using them to capture a single tobacco mosaic virus and the bacterium Escherichia coli. During the years 1990 and thereafter, researchers such as Carlos Bustamante, James Spudich, and Steven block initiate the use of optical trap force spectroscopy to characterize the molecular-scale biological activator. Motor drive is often found in molecular biology, and are responsible for the mechanical motion and action in the cell. Biophysicist optical trap allows to observe the style and driving dynamics of nanoscale single molecule level, trapper-style optical spectroscopy has led to greater understanding of the origins of the style-forming molecular stochastic.
Optical trap has proven very useful in areas outside of biology as well. For brevity, in 2003 the optical trap technique has been applied in the sorting of cells: the formation of large-scale optical intensity pattern imposed on the sample area, the cells can be sorted into each of the intrinsic optical characteristics. Optical trap has also been used to investigate the cytoskeleton, the measurement of visco-elastic properties of biopolymers, and the study of cell death.
Aspects of Optical Physics trapper
General Explanation
Optical Tweezers are able to manipulate even micro-sized dielectric particles in the nanometer scale by deploying the force is very small in the extreme through a focused laser beam. This file is usually focused by passing into the microscope objective. Thinnest point of the laser beam is called the beam waist (beam waist, because it looks like a waist, hips especially women), which consists of very large electric field gradients. This leads to a dielectric particle is pulled along the gradient towards the region with the largest electric field which is located in the center beam. Laser light also tends to wear the force on the particles in the beam along the beam propagation direction. This statement can be easily understood when one considers that light behaves as a collection of particles, wherein each particle of light involves a small dielectric particles in its path. This is known as the scattering force and the result is a particle can be moved into the center of the beam waist. As shown in FIG.
Optical trap is a very sensitive instrument and is able to manipulate and detect movement in the sub-nanometer scale for dielectric particles of sub-micrometer scale. For this reason, the optical trap is often used to manipulate and study single molecules with menginteraksikan didempetkan granular particles on the molecule to be studied. DNA, proteins, and enzymes that interact with it is usually studied in this way.
For quantitative scientific measurement, most of the optical trap is operated in a manner in which the dielectric particle rarely moves far from the center of the trap. The reason is that the force applied to the particle is linear to the displacement of the center of the trap along the displacement is quite small. In this way, optical traps can be let as a simple spring system that follows Hooke's law.More detailed explanation of the optical trap
A more precise explanation regarding the behavior of the optical trap depends on the size of the trapped particle relative to the wavelength of laser light used to trap particles. In cases where the dimensions of the particles larger than the wavelength, a simple ray optics treatment is quite fulfilling. If the wavelength of light is quite large compared with the dimensions of the particles, the particles can be considered as an electric dipole in an electric field. For the optical trap, the dimensions of the dielectric particles with a large order of the wavelength of the trap beam, an accurate model for this condition is time-dependent Maxwell's equations and harmonic Maxwell's equations using the appropriate boundary conditions.
Approach Light Optics
In cases where the diameter of the trapped particles is quite large compared to the wavelength of light, a phenomenon described perangkapan can both use light optics. As shown in the figure, a single light beam emitted from the laser will terefraksi granular particles after passing through the dielectric. As a result, the beam will come out with a different direction from the direction before going through the grain. Because light has momentum, change in direction of light indicates a change in momentum. Berdaraskan Newton's third law, there should be a big change in the same momentum in the opposite direction on the particle.
Most optical traps to work with a gaussian beam (TEM00 mode). In this case, if the particles move from the center beam, as shown in the picture, then the particle has a net force that returns particles back into the center of the trap because most files provide a larger momentum change towards the trap center at a fraction of the file that gives the change of momentum which leads out of the trap center.
If the particles are in the center beam, the single light beam through the particle will terefraksi symmetrically, and this produces laterally zero net force. Net style in this case is along the axial direction of the trap, which eliminates the mutual force of laser light scattering. Removal of the axial gradient force with the scattering force is what causes the granular particles are trapped inside the stable beam waist.
source : http://kurniafisika.wordpress.com/2010/10/16/optical-tweezer-penjebak-optikal-sebuah-penggerak-nano-berbasis-optik/
Tidak ada komentar:
Posting Komentar