Newly demonstrated capabilities of low-powered nanotweezers may benefit cellular-level studies
Using ultra-low input power densities, researchers at the University of Illinois at Urbana-Champaign have demonstrated for the first time how low-power “optical nanotweezers” can be used to trap, manipulate, and probe nanoparticles, including fragile biological samples.
“We used an average power of 50 microwatts to trap, manipulate, and probe nanoparticles. This is 100x less power than what you would get from a standard laser pointer.”
In their recent paper, “Femtosecond-pulsed plasmonic nanotweezers” published in the September 17 issue of Scientific Reports; doi:10.1038/srep00660), the researchers describe how a femtosecond-pulsed laser beam significantly augments the trapping strength of Au bowtie nanoantennas arrays (BNAs), and the first demonstration of use of femtosecond (fs) source for optical trapping with plasmonic nanotweezers.
“Our system operates at average power levels approximately three orders of magnitude lower than the expected optical damage threshold for biological structures, thereby making this technology very attractive for biological (lab-on-a-chip) applications such as cell manipulation,” added Toussaint, who is also an affiliate faculty member in the Department of Bioengineering and the Department of Electrical and Computer Engineering. “This system offers increased local diagnostic capabilities by permitting the probing of the nonlinear optical response of trapped specimens, enabling studies of in vitro fluorescent-tagged cells, or viruses using a single line for trapping and probing rather than two or more laser lines.”
The paper also demonstrated enhancement of trap stiffness of up to 2x that of a comparable continuous-wave (CW) nanotweezers and 5x that of conventional optical tweezers that employ a fs source; successful trapping and tweezing of spherical particles ranging from 80-nm to 1.2-um in diameter, metal, dielectric, and both fluorescent and non- fluorescent particles; enhancement of two-photon fluorescent signal from trapped microparticles in comparison to the response without the presence of the BNAs; enhancement of the second-harmonic signal of ~3.5x for the combined nanoparticle-BNA system compared to the bare BNAs; and fusing of Ag nanoparticles to the BNAS.
Contact: Kimani C. Toussaint, Jr., Department of Mechanical Science & Engineering, 217/244-4088.
If you have any questions about the College of Engineering, or other story ideas, contact Rick Kubetz, writer/editor, Engineering Communications Office, 217/244-7716, University of Illinois at Urbana-Champaign.