Engineers demonstrate a new type of optical tweezer

February 25, 2008

CAMBRIDGE, Mass. -- February 25, 2008 -- Researchers at the Harvard School of Engineering and Applied Sciences (SEAS) demonstrated a new type of optical tweezer with the potential to make biological and microfluidic force measurements in integrated systems such as microfluidic chips. The tweezer, consisting of a Fresnel Zone Plate microfabricated on a glass slide, has the ability to trap particles without the need for high performance objective lenses.

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.
-end-
The work was supported by the Microsystems Technology Office of the Defense Advanced Research Projects Agency and the Harvard Nanoscale Science and Engineering Center of the National Science Foundation.

Harvard University

Related Engineering Articles from Brightsurf:

Re-engineering antibodies for COVID-19
Catholic University of America researcher uses 'in silico' analysis to fast-track passive immunity

Next frontier in bacterial engineering
A new technique overcomes a serious hurdle in the field of bacterial design and engineering.

COVID-19 and the role of tissue engineering
Tissue engineering has a unique set of tools and technologies for developing preventive strategies, diagnostics, and treatments that can play an important role during the ongoing COVID-19 pandemic.

Engineering the meniscus
Damage to the meniscus is common, but there remains an unmet need for improved restorative therapies that can overcome poor healing in the avascular regions.

Artificially engineering the intestine
Short bowel syndrome is a debilitating condition with few treatment options, and these treatments have limited efficacy.

Reverse engineering the fireworks of life
An interdisciplinary team of Princeton researchers has successfully reverse engineered the components and sequence of events that lead to microtubule branching.

New method for engineering metabolic pathways
Two approaches provide a faster way to create enzymes and analyze their reactions, leading to the design of more complex molecules.

Engineering for high-speed devices
A research team from the University of Delaware has developed cutting-edge technology for photonics devices that could enable faster communications between phones and computers.

Breakthrough in blood vessel engineering
Growing functional blood vessel networks is no easy task. Previously, other groups have made networks that span millimeters in size.

Next-gen batteries possible with new engineering approach
Dramatically longer-lasting, faster-charging and safer lithium metal batteries may be possible, according to Penn State research, recently published in Nature Energy.

Read More: Engineering News and Engineering Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.