The device was designed, fabricated, and tested by postdoctoral fellow Ethan Schonbrun and undergraduate researcher Charles Rinzler under the direction of Assistant Professor of Electrical Engineering Ken Crozier (all are affiliated with SEAS). The team's results were published in the February 18th edition of Applied Physics Letters and the researchers have filed a U.S. provisional patent covering this new device.
"The microfabricated nature of the new optical tweezer offers an important advantage over conventional optical tweezers based on microscope objective lenses," says Crozier. "High performance objective lenses usually have very short working distances -- the trap is often ~200 mm or less from the front surface of the lens. This prevents their use in many microfluidic chips since these frequently have glass walls that are thicker than this."
The researchers note that the Fresnel Zone Plate optical tweezers could be fabricated on the inner walls of microfluidic channels or even inside cylindrical or spherical chambers and could perform calibrated force measurements in a footprint of only 100x100μm.
Traditional tweezers, by contrast, would suffer from crippling aberrations in such locations. Moreover, in experimental trials, the optical tweezers exhibited trapping performance comparable to conventional optical tweezers when the diffraction efficiency was taken into account.
The researchers envision using their new tweezer inside microfluidic chips to carry out fluid velocity, refractive index, and local viscosity measurements. Additional applications include biological force measurements and sorting particles based on their size and refractive index. Particle-sorting chips based on large arrays of tweezers could be used to extract the components of interest of a biological sample in a high-throughput manner.
Source: Harvard University
Related stories:
Magnetic Computer Sensors May Help Study Biomolecules
Magnetic switches like those in computers also might be used to manipulate individual strands of DNA for high-speed applications such as gene sequencing, experiments at the National Institute of Standards and Technology suggest.
New 3D Magnetic Tweezers
Professor Gwo-Bin Vincent Lee, from National Cheng Kung University, Taiwan, and his colleagues have manufactured three-dimensional, micromachined magnetic tweezers to manipulate DNA molecules. Their method was published in the February 7, 2006 issue of
Nanotechnology.
Optoelectronic tweezers to round up cells, microparticles
Rounding up wayward cells and particles on a microscope slide can be as difficult as corralling wild horses on the range, particularly if there's a need to separate a single individual from the group.
But now, a new device developed by University of California, Berkeley, engineers, and dubbed an "optoelectronic tweezer," will enable researchers to easily manipulate large numbers of single cells and particles using optical images projected onto a glass slide coated with photoconductive materials.
Electric-Field-Induced Phase-Separation of Liquid Mixtures
Researches have shown that electric fields can control the phase separation behaviour of mixtures of simple liquids under practical conditions, provided that the fields are non-uniform. This direct control over phase separation behaviour depends on field intensity, with the electrode geometry determining the length-scale of the effect. This phenomenon will find a number of
nanotechnological applications, particularly as it benefits from field gradients near small conducting objects.
Light throws a curve ball
(PhysOrg.com) -- Researchers at the University of St Andrews have made a surprise discovery using light beams that can travel around corners.
Tweezers Trap Nanotubes by Color
Singled-walled carbon nanotubes are graphene sheets wrapped into tubes, and are typically made up of various sizes and with different amounts of twist (also known as chiralities). Each type of nanotube has its own electronic and optical properties. Physicists at Osaka University in Japan used colored light to selectively manipulate different types of carbon nanotubes. They found that some of nanotubes displayed a tendency to cluster at the focal area of a focused laser beam.
Disposable 'lab-on-a-chip' may save costs and lives
(PhysOrg.com) -- Low-cost, disposable cartridges that would let doctors perform diagnostic tests at the point-of-care could speed up diagnosis and treatment while lowering costs. European researchers are rapidly closing in on that goal.
A new 'Pyrex' nanoparticle
Researchers in Switzerland have developed a new method to fabricate borosilicate glass nanoparticles. Used in microfluidic systems, these "Pyrex"-like nanoparticles are more stable when subjected to temperature fluctuations and harsh chemical environments than currently used nanoparticles made of polymers or silica glass. Their introduction could extend the range of potential nanoparticle applications in biomedical, optical and electronic fields.
