Experimental setup schematic showing laser source, microscope, and imaging detector and spectrometer. The inset illustrates the two different sample configurations that were explored; red arrows correspond to the input polarization directions and black arrows depict the propagation vector.
“We already know that plasmonic nanoantennas enhance local fields by up to several orders of magnitude, and thus, previously showed that we can use these structures with a regular CW laser source to make very good optical tweezers,” explains, Kimani Toussaint, Jr., assistant professor of mechanical science and engineering at Illinois. “This is exciting because, for the first time, we’re showing that, the near-field optical forces can be enhanced even further, without doing anything extra in terms of fabrication, but rather simply by exploiting the high-peak powers associated with using a femtosecond (fs) optical source.
“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.”
"We present strong evidence that a fs source could actually augment the near-field optical forces produced by the BNAs, and most likely, other nanoantenna systems, as well. To our knowledge, this has never been demonstrated,” said Brian Roxworthy, a graduate student in Toussaint’s PROBE (Photonics Research of Bio/nano Environments) lab group and first author of the paper. According to Roxworthy, the demonstration of controlled particle fusing could be important for creating novel nanostructures, as well as for enhancing the local magnetic field response, which will be important for the field of magnetic plasmonics.
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.
Kimani C. Toussaint, Jr. | EurekAlert!
Researchers use light to remotely control curvature of plastics
23.03.2017 | North Carolina State University
TU Graz researchers show that enzyme function inhibits battery ageing
21.03.2017 | Technische Universität Graz
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
27.03.2017 | Earth Sciences
27.03.2017 | Life Sciences
27.03.2017 | Life Sciences