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!
Neutrons pave the way to accelerated production of lithium-ion cells
20.03.2018 | Technische Universität München
Monocrystalline silicon thin film for cost-cutting solar cells with 10-times faster growth rate fabricated
16.03.2018 | Tokyo Institute of Technology
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
22.03.2018 | Trade Fair News
22.03.2018 | Earth Sciences
22.03.2018 | Earth Sciences