27 research outputs found
Optofluidic transport and particle trapping using an all-dielectric quasi-BIC metasurface
Manipulating fluids by light at the nanoscale has been a long-sought-after
goal for lab-on-a-chip applications. Plasmonic heating has been demonstrated to
control microfluidic dynamics due to the enhanced and confined light absorption
from the intrinsic losses of metals. Dielectrics, counterpart of metals, is
used to avoid undesired thermal effects due to its negligible light absorption.
Here, we report an innovative optofluidic system that leverages a quasi-BIC
driven all-dielectric metasurface to achieve nanoscale control of temperature
and fluid motion. Our experiments show that suspended particles down to 200
nanometers can be rapidly aggregated to the center of the illuminated
metasurface with a velocity of tens of micrometers per second, and up to
millimeter-scale particle transport is demonstrated. The strong electromagnetic
field enhancement of the quasi-BIC resonance can facilitate increasing the flow
velocity up to 3-times compared with the off-resonant situation. We also
experimentally investigate the dynamics of particle aggregation with respect to
laser wavelength and power. A physical model is presented to elucidate the
phenomena and surfactants are added to the particle colloid to validate the
model. Our study demonstrates the application of the recently emerged
all-dielectric thermonanophotonics in dealing with functional liquids and opens
new frontiers in harnessing non-plasmonic nanophotonics to manipulate
microfluidic dynamics. Moreover, the synergistic effects of optofluidics and
high-Q all-dielectric nanostructures can hold enormous potential in
high-sensitivity biosensing applications
Scalable trapping of single nanosized extracellular vesicles using plasmonics
Heterogeneous nanoscale particles released by cells known as extracellular
vesicles (EVs) are actively investigated for early disease detection1,
monitoring2, and advanced therapeutics3. Due to their extremely small size, the
stable trapping of nano-sized EVs using diffraction-limited optical tweezers4
has been met with challenges. Plasmon-enhanced optical trapping can confine
light to the nanoscale to generate tight trapping potentials. Unfortunately, a
long-standing challenge is that plasmonic tweezers have limited throughput and
cannot provide rapid delivery and trapping of particles at plasmonic hotspots
while precluding the intrinsic plasmon-induced photothermal heating effect at
the same time. We report our original geometry-induced electrohydrodynamic
tweezers (GET) that generate multiple electrohydrodynamic potentials for the
parallelized transport and trapping of single EVs in parallel within seconds
while enhancing the imaging of single trapped EVs. We show that the integration
of nanoscale plasmonic cavities at the center of each GET trap results in the
parallel placement of single EVs near plasmonic cavities enabling instantaneous
plasmon-enhanced optical trapping upon laser illumination without any
detrimental heating effect for the first time. These non-invasive scalable
hybrid nanotweezers open new horizons for high-throughput tether-free
plasmon-enhanced single EV trapping and spectroscopy. Other potential areas of
impact include nanoplastics characterization, and scalable hybrid integration
for quantum photonics.Comment: 21 pages, 5 figure
Merging toroidal dipole bound states in the continuum without up-down symmetry in Lieb lattice metasurfaces
The significance of bound states in the continuum (BICs) lies in their
potential for theoretically infinite quality factors. However, their actual
quality factors are limited by imperfections in fabrication, which lead to
coupling with the radiation continuum. In this study, we present a novel
approach to address this issue by introducing a merging BIC regime based on a
Lieb lattice. By utilizing this approach, we effectively suppress the
out-of-plane scattering loss, thereby enhancing the robustness of the structure
against fabrication artifacts. Notably, unlike previous merging systems, our
design does not rely on the up-down symmetry of metasurfaces. This
characteristic grants more flexibility in applications that involve substrates
and superstrates with different optical properties, such as microfluidic
devices. Furthermore, we incorporate a lateral band gap mirror into the design
to encapsulate the BIC structure. This mirror serves to suppress the in-plane
radiation resulting from finite-size effects, leading to a remarkable ten-fold
improvement in the quality factor. Consequently, our merged BIC metasurface,
enclosed by the Lieb lattice photonic crystal mirror, achieves an exceptionally
high-quality factor of 105 while maintaining a small footprint of 26.6X26.6 um.
Our findings establish an appealing platform that capitalizes on the
topological nature of BICs within compact structures. This platform holds great
promise for various applications, including optical trapping, optofluidics, and
high-sensitivity biodetection, opening up new possibilities in these fields
Towards rapid extracellular vesicles colorimetric detection using optofluidics-enhanced color-changing optical metasurface
Efficient transportation and delivery of analytes to the surface of optical
sensors are crucial for overcoming limitations in diffusion-limited transport
and analyte sensing. In this study, we propose a novel approach that combines
metasurface optics with optofluidics-enabled active transport of extracellular
vesicles (EVs). By leveraging this combination, we show that we can rapidly
capture EVs and detect their adsorption through a color change generated by a
specially designed optical metasurface that produces structural colors. Our
results demonstrate that the integration of optofluidics and metasurface optics
enables robust colorimetric read-out for EV concentrations as low as 107
EVs/ml, achieved within a short incubation time of two minutes, while using a
CCD camera or naked eye for the read-out. This approach offers the potential
for rapid sensing without the need for spectrometers and provides a short
response time. Our findings suggest that the synergy between optofluidics and
metasurface platforms can enhance the detection efficiency of low concentration
bioparticle samples by overcoming the diffusion limits
Multiplexed long-range electrohydrodynamic transport and nano-optical trapping with cascaded bowtie photonic crystal cavities
Photonic crystal cavities have been widely studied for optical trapping due
to their ability to generate high quality factor resonances. However, prior
photonic crystal nanotweezers possess mode volumes significantly larger than
those of plasmonic nanotweezers, which limit the gradient force. Additionally,
they also suffer from low particle capture rates. In this paper, we propose a
nanotweezer system based on a 1D bowtie photonic crystal nanobeam that achieves
extreme mode confinement and an electromagnetic field enhancement factor of 68
times, while supporting a high-quality factor of 15,000 in water. Furthermore,
by harnessing the localized heating of a water layer near the bowtie cavity
region, combined with an applied alternating current electric field, our system
provides long-range transport of particles with average velocities of 5
m/s towards the bowtie cavities on demand. Once transported to the
bowtie cavity region, our results show that a 20 nm quantum dot will be
confined in a potential well with a depth of 35 T. Thus, our approach
effectively addresses the challenge of limited capture rate in photonic crystal
nanotweezers for the first time. Finally, we present the concept of multiplexed
long-range transport for hand-off of a single emitter from one cavity to the
next by simply switching the wavelength of the input light. This novel
multiplexed integrated particle trapping platform is expected to open new
opportunities in directed assembly of nanoscale quantum emitters and
ultrasensitive sensors for single particle spectroscopy.Comment: 11 pages, 4 figure
Single-peak and narrow-band mid-infrared thermal emitters driven by mirror-coupled plasmonic quasi-BIC metasurfaces
Wavelength-selective thermal emitters (WS-EMs) hold considerable appeal due
to the scarcity of cost-effective, narrow-band sources in the mid-to-long-wave
infrared spectrum. WS-EMs achieved via dielectric materials typically exhibit
thermal emission peaks with high quality factors (Q factors), but their optical
responses are prone to temperature fluctuations. Metallic EMs, on the other
hand, show negligible drifts with temperature changes, but their Q factors
usually hover around 10. In this study, we introduce and experimentally verify
a novel EM grounded in plasmonic quasi-bound states in the continuum (BICs)
within a mirror-coupled system. Our design numerically delivers an
ultra-narrowband single peak with a Q factor of approximately 64, and
near-unity absorptance that can be freely tuned within an expansive band of
more than 10 {\mu}m. By introducing air slots symmetrically, the Q factor can
be further augmented to around 100. Multipolar analysis and phase diagrams are
presented to elucidate the operational principle. Importantly, our infrared
spectral measurements affirm the remarkable resilience of our designs'
resonance frequency in the face of temperature fluctuations over 300 degrees
Celsius. Additionally, we develop an effective impedance model based on the
optical nanoantenna theory to understand how further tuning of the emission
properties is achieved through precise engineering of the slot. This research
thus heralds the potential of applying plasmonic quasi-BICs in designing
ultra-narrowband, temperature-stable thermal emitters in mid-infrared.
Moreover, such a concept may be adaptable to other frequency ranges, such as
near-infrared, Terahertz, and Gigahertz.Comment: 39 pages, 12 figure
Long-range and rapid transport of individual nano-objects by a hybrid electrothermoplasmonic nanotweezer
Plasmon-enhanced optical trapping is being actively studied to provide efficient manipulation of nanometre-sized objects. However, a long-standing issue with previously proposed solutions is how to controllably load the trap on-demand without relying on Brownian diffusion. Here, we show that the photo-induced heating of a nanoantenna in conjunction with an applied a.c. electric field can initiate rapid microscale fluid motion and particle transport with a velocity exceeding 10 μm s -1 , which is over two orders of magnitude faster than previously predicted. Our electrothermoplasmonic device enables on-demand long-range and rapid delivery of single nano-objects to specific plasmonic nanoantennas, where they can be trapped and even locked in place. We also present a physical model that elucidates the role of both heat-induced fluidic motion and plasmonic field enhancement in the plasmon-assisted optical trapping process. Finally, by applying a d.c. field or low-frequency a.c. field (below 10 Hz) while the particle is held in the trap by the gradient force, the trapped nano-objects can be immobilized into plasmonic hotspots, thereby providing the potential for effective low-power nanomanufacturing on-chip
Roadmap for Optical Tweezers 2023
Optical tweezers are tools made of light that enable contactless pushing, trapping, and manipulation of objects ranging from atoms to space light sails. Since the pioneering work by Arthur Ashkin in the 1970s, optical tweezers have evolved into sophisticated instruments and have been employed in a broad range of applications in life sciences, physics, and engineering. These include accurate force and torque measurement at the femtonewton level, microrheology of complex fluids, single micro- and nanoparticle spectroscopy, single-cell analysis, and statistical-physics experiments. This roadmap provides insights into current investigations involving optical forces and optical tweezers from their theoretical foundations to designs and setups. It also offers perspectives for applications to a wide range of research fields, from biophysics to space exploration
Minimal information for studies of extracellular vesicles (MISEV2023): From basic to advanced approaches
Extracellular vesicles (EVs), through their complex cargo, can reflect the state of their cell of origin and change the functions and phenotypes of other cells. These features indicate strong biomarker and therapeutic potential and have generated broad interest, as evidenced by the steady year-on-year increase in the numbers of scientific publications about EVs. Important advances have been made in EV metrology and in understanding and applying EV biology. However, hurdles remain to realising the potential of EVs in domains ranging from basic biology to clinical applications due to challenges in EV nomenclature, separation from non-vesicular extracellular particles, characterisation and functional studies. To address the challenges and opportunities in this rapidly evolving field, the International Society for Extracellular Vesicles (ISEV) updates its 'Minimal Information for Studies of Extracellular Vesicles', which was first published in 2014 and then in 2018 as MISEV2014 and MISEV2018, respectively. The goal of the current document, MISEV2023, is to provide researchers with an updated snapshot of available approaches and their advantages and limitations for production, separation and characterisation of EVs from multiple sources, including cell culture, body fluids and solid tissues. In addition to presenting the latest state of the art in basic principles of EV research, this document also covers advanced techniques and approaches that are currently expanding the boundaries of the field. MISEV2023 also includes new sections on EV release and uptake and a brief discussion of in vivo approaches to study EVs. Compiling feedback from ISEV expert task forces and more than 1000 researchers, this document conveys the current state of EV research to facilitate robust scientific discoveries and move the field forward even more rapidly