The mechanics of filament networks depend on both the individual filament properties and the network architecture. Despite the importance of filament networks in biology, there exists no technique which can precisely localize filaments and cross-links in three dimensions and simultaneously resolve their dynamics. Thermal noise imaging is a three-dimensional scanning probe technique that utilizes the confined thermal motion of an optically trapped nanoparticle to noninvasively probe the sample. Here, we apply the technique to a stably crosslinked network of microtubules. The filament axes are localized with a precision of 4nm. Analysis also reveals fluctuations of individual filaments and properties of cross-links.

A challenge within the motor biophysics field is reconstituting a motor-filament environment that reflects physiological function. Many optical trapping studies of motor proteins employ a reductionist geometry of a single motor interacting with a single filament. These conformations do not accurately represent the structural architecture in which motors with crosslinking ability, such as myosins or mitotic kinesins, function. Thus, we engineered customizable “nanocells” of reconstituted protein assemblies to probe hierarchical cytoskeletal mechanics with high resolution using optical tweezers.

The use of laser nanosurgery to induce photolysis has proven to be an indispensable tool for in vitro studies of astrocytes. Here, we utilize laser nanosurgery to initiate damage within single astrocytes in an vitro traumatic brain injury model. Changes in cytoplasmic ATP levels were observed throughout the astrocyte network following the targeted lysis of a single cell. In response to the death of a neighboring cell, a transient drop in cytoplasmic ATP levels was observed. This combined method of optical technologies should prove valuable in understanding astrocytes’ role in detection of nervous tissue damage.

This presentation will focus on enhancing the usability of double-nanohole (DNH) optical tweezers in protein analysis applications. We will compare the technique with existing label-free and tether-free methods, showing that the DNH has an order of magnitude lower limit of detection and higher sensitivity. We will also present advances for low-cost and high-througput analysis, with applications to drug discovery, drug validation and biologics. We will also discuss applications to the analysis of perovskite quantum dots.

Precise and non-invasive control over single particles is key for a range of physical and bio-medical applications, such as microfluidics and biophysics. The analysis of the rotation dynamics of an optically trapped dielectric microparticle is presented as a novel tool to characterize the properties of a liquid medium at the microscale (temperature, viscosity and bio-objects). In this work, single dielectric β-NaYF4:Ln3+ microparticles are used as optical sensors and the analysis of its damped rotational dynamics allowed not only the controlled and remote manipulation of the sensor, but also an improved characterization of the medium and fast recording of its content.

We demonstrate a multi-core fiber (MCF)-based optical trap that enables dynamically controlled rotation of cancer cells around all 3D axes for optical diffraction tomography with high spatiotemporal resolution. We introduce a novel deep neural network to accelerate the tailored hologram and enable the generation of complex light fields near the video rate in the high-fidelity capture region. The flexibility of fiber optic manipulation of multi-axis cell rotations opens up new applications for 3D refractive index reconstruction. Deep neural networks bring the MCF-based optical manipulation system to the next level of freedom and open new perspectives for non-contact cellular studies.

Nanofabrication using two-photon-photopolymerision (2PP) can be used to create complex 3D structures with sub-diffraction-limited resolution for studying a range of microscopic systems. In this work we discuss how the addition of a spatial light modulator (SLM) can optimise the printing process through in-situ aberration correction and wavefront engineering. We show how digital holograms are used to control and fabricate complex patterns using various Gerchberg-Saxton algorithms. We demonstrate the necessity for aberration correction when printing using many independently controlled foci and fabricate devices that are used to study complex biological systems.

In the framework of novel medical paradigm the red blood cells (RBC) have a great potential to be used as drug delivery carriers. This approach is required an ultimate understanding of the peculiarities of mutual interaction of RBC influenced by nano-materials composed the drugs. The Optical Tweezers (OT) is the cutting-edge optical technology and widely used to explore mechanisms of cells interaction with the ability to trap non-invasively, manipulate and displace living cells with a notably high accuracy. In the current study, the mutual interaction of RBC with laser-synthesized plasmonic nanoparticles (NP) is investigated.

The conservation orbital angular momentum and polarization for beams propagating through scattering bio-soft matter enables multiplexed signaling. By utilizing nonlinear optical effects in the scattering bio-soft-matter, we investigate the conservation of polarization and OAM through self-trapping and pump/probe coupled waveguides of light in sheep red blood cell suspensions at 532 nm and 780nm wavelengths. This study provides a basis for further exploration into optical signaling in soft matter systems.

This conference presentation was prepared for the Optical Trapping and Optical Micromanipulation XIX conference at SPIE Optics + Photonics 2022.

Two common assumptions for simple molecular liquids are that they exhibit a Newtonian response and the no-slip boundary condition at solid-liquid interfaces. By making ultrafast optical measurements of vibrating metal nanoparticles in simple liquids, we have shown that these assumptions can break down on nanometer length scales and on the picosecond time scales that are characteristic of nanoscale motion. Our measurements quantitatively validate a Maxwell model for viscoelasticity in simple, compressible liquids, and provide a measurement of single-nanometer-scale slip lengths at the nanoparticle-liquid interface.

Optical Trapping continues to make enormous impact across the sciences. This talk will describe how novel nanostructured materials can assist in trapping performance. This includes near field trapping and the use of metasurfaces. Separately the talk will discuss the use of novel materials for trapped particles to enhance performance for trapping in liquid and vacuum.

The use of a patterned surface to create an optical conveyor for spherical, and near spherical particles is explored. Using a surface constructed of a repeating micron-sized motif, we simulate the effects of moving a particle in the near-field region above the surface, as well as exploring optical force changes in the axis perpendicular to the surface resulting from changes in size of the particles, and the choice of incident wavelength.

An optically levitated nanoparticle in a vacuum is excellent for precision measurements. We have optically levitated silica nanodumbbells in a vacuum and driven them to rotate beyond 5 GHz. With an optically levitated nanorotor, we demonstrated a torque sensor with a record-high sensitivity [Nature Nanotechnology, 15, 89 (2020)]. Recently, we designed and fabricated an ultrathin metalens with a high numerical aperture (NA=0.88) and used it to levitate a nanoparticle in a vacuum [Optica, 8, 1359 (2021)]. Such a system will provide opportunities for on-chip sensing. In addition, we have trapped a nanodumbbell near a surface with a separation of less than one micrometer, and used it to demonstrate an optically levitated scanning probe microscope beyond the diffraction limit. Our work will be important for studying quantum surface interactions.

I will present an overview of recent experiments conducted at the optical tweezers (OT) group at UFRJ, including the demonstration of a negative optical torque, axial position detection and the measurement of a fN attractive Casimir force signal in the distance range from 200 to 500 nm. I will also discuss proposals of enantioselective optical manipulation and characterization of chiral materials which are based on a theoretical model for the optical force and torque in presence of chirality.

We present a computational study of the trapping, packing and dynamics of clusters of Rayleigh particles in optical vortices. We examine the effect of OAM on the cylindrical packing arrangements and dynamics of the clusters, drawing comparisons with macroscopic systems of beads in fluid vortices.

The ability to control nanoscale motions of nanomaterials is expected to play significant roles in various fields such as photophysics, photochemistry and biological applications. For the optical nanomanipulation, metal nanoantenna structures are widely used. These plasmonic structures can confine light into nano-sized volumes and enhance the nanoscale light-matter interactions. In this paper, we demonstrated that precise orbital rotational motion is driven by the angular momentum that is transferred from photon to plasmonic nanoantenna. We present the numerical simulation results and discussion on the mechanism of the angular momenta transfer. Then, we show the experimental results on the rotational manipulation of a nanodiamond using plasmonic trimer structure.

Nano-motors driven by linearly polarized light were fabricated and measured experimentally. These structures include a plasmonic rotor embedded into a SiO2 body. The rotor geometry was optimized to reach the strongest torque using a convolutional neural network connected to a deep convolution generative adversarial network. The most promising nanostructures were fabricated with a multistep process that included ion beam etching of the rotor, followed by embodiment in SiO2. Careful optimization enabled the realization of sub-20 nm features. The nano-motors were transferred to a fluidic chamber for optical characterization, demonstrating rapid rotation speeds.

Using optical tweezers, we isolate individual aerosol particles in order to study their charging dynamics. Preliminary results suggest that the rate at which particles charge depends on material, surface area, and most importantly, the humidity of the surrounding air. We hypothesize that charging occurs due to preferential adsorption/desorption of OH- or H+ ions. Further still, when we artificially increase the number of ions surrounding our particle, we observe rapid discharging. These results could have important implications to numerous fields including cloud formation and dust storm electrification, through to pollination; anywhere micro-particle charging plays a crucial role.

The optically powered train of microparticles waveguide the light, stabilized itself and move forward due to strong optical forces. This phenomenon is similar to the soliton creation in microparticles solution, but here particles develop one after another from the reservoir in direction of light propagation, similarly to a chain developing from a spool or a train. We experimentally study the effect and numerically evaluate the forces acting on microparticles in the chain. We find different regimes of behavior depending on the microparticles size.

Light is routinely used to steer the motion of atoms in free space, enabling cooling and trapping of matter waves through ponderomotive interaction and Doppler-mediated photon scattering. In parallel, optical interaction with free electrons has recently emerged as a powerful way to modulate the electron wave function for applications in ultrafast electron microscopy. Here, we combine these two worlds by theoretically demonstrating that matter waves can be optically manipulated by inelastic interaction with optical fields, allowing us to modulate the translational wave function and produce temporally and spatially compressed atomic beam pulses.

We present a new class of ultra-high-Q nanomechanical resonators based on torsion modes of high-stress nanoribbons, and explore their application for quantum optomechanics experiments and precision optomechanical sensing. Specifically, we show that nanoribbons made of high stress silicon nitride support torsion modes which are naturally soft-clamped, yielding dissipation dilution factors as high as 10^4 and Q factors as high as 10^8 for the fundamental mode. We show that these modes can be read out with optical lever measurements with an imprecision below that at the standard quantum limit, paving the way for a new branch of torsional quantum optomechanics. We also show that nanoribbons can be mass-loaded without changing their torsional Q factor. We use this strategy to engineer a chip-scale torsion balance with an damping rate of 10 micro-hertz. We use this torsion balance as a clock gravimeter to sence micro-g fluctuation in the local gravitational field strength.

We present the first experimental optical trapping of ytterbium-doped sodium yttrium fluoride (Yb:NaYF4) hexagonal microdisks with a dual-beam dipole trap. These high-aspect-ratio hexagonal microdisks exhibit reduced photon recoil heating due to light scattering while allowing for 10s of kHz mechanical frequencies. These features make them good candidates as force sensors for the Levitated Sensor Detector (LSD) project, which detects high-frequency gravitational waves above the region previously probed by LIGO. We discuss motional dynamics of these microdisks by showing their motional spectra in comparison with analytical and numerical models and the recent progress of 1-meter LSD prototype that is under development at Northwestern University.

Highly sensitive levitated optomechanical systems can be used as precise acceleration and force sensors to search for fundamental physics. Eliminating the net charge on these systems reduces the most significant coupling to external electric fields yet leaves the issue of backgrounds created by higher order multipole moments in the charge distribution of the levitated sensors. In many high sensitivity applications of levitated optomechanical sensors, dipole induced forces can be many orders of magnitude larger than the forces of interest. Thus, techniques to measure, control, and ultimately eliminate dipole generated backgrounds may be required to realize numerous experiments such as the search for millicharged particles, the exploration of new parameter space of dark matter mass with an array of levitated microspheres and possibly future work towards detection of gravitational entanglement between micron sized masses. This talk will discuss the application of controlled precessive torques to the electric dipole moment of a levitated microsphere in vacuum to reduce dipole-induced backgrounds by 2 orders of magnitude as well as work towards integrating such sensors in large arrays.

In optical tweezers, reductions in the symmetry of the particle or trapping field introduce nonconservative optical forces, producing a variety of nonequilibrium effects. Here we show nonconservative optical traps in a vacuum using birefringent microspheres in linearly polarised (LP) and circularly polarised (CP) Gaussian beams. Coherent and self-sustained oscillations emerge in LP due to nonsymmetric coupling between rotational and translational degrees of freedom, while stochastic orbital rotation and coherent limit cycles arise in CP about the beam axis. These nonconservative effects play a critical role in the rotational dynamics of a levitated birefringent microsphere.

We will report on recent progress in our levitated optomechanics experiment. We exploit a coherent scattering approach which has allowed a significant acceleration of the field in recent years. In this setting, a tweezer levitated nanoparticle interacts with the optical field of a Fabry-Perot cavity which is driven solely by light resonantly scattered by the particle itself. The interaction with the cavity field leads to a cross-coupling of the motional degrees of freedom (DoF) in the tweezer polarization plane so that the two DoFs are mixed. We will experimentally show that away from the cavity node, where most experiments have been working, there is a “sweet spot” where competing processes prevent the cavity from mixing these DoFs. While currently in the weak coupling regime, this effect could prevent the formation of bright/dark modes when the strong coupling is reached.

We explore Anderson-localized cavity optomechanics in a two-dimensional optomechanical platform: a waveguide etched in a suspended silicon membrane with an air slot. Inherent, unavoidable fabrication imperfections induce sufficient backscattering to realize Anderson-localized optical modes which can be driven to enable phonon lasing via optomechanical back-action. We observe mechanical lasing up to 6.8 GHz that results from confinement of the mechanical mode. The role of disorder in cavity optomechanics has thus far been largely overlooked, though our results indicate that it can have a decisive impact on device functionality and opens perspectives for studies of multiple scattering and Anderson localization of bosonic excitations with parametric coupling to mechanical degrees of freedom.

Optically trapped nanoparticles can be used to explore heat conduction in gases. Heat conduction can be modeled using Fourier’s law when the mean-free path (MFP) of the gas molecules is short compared to the size of the heat source. When the MFP of the gas is larger than the size of the heated nanoparticle a nanoscopic approach which considers the gas’s interactions is needed. We use nanodiamonds with nitrogen-vacancy centers to measure the temperature of a trapped nanoparticle and observe both continuum (Fourier) and sub-continuum regions of heat conduction and the transition between them.

We have proposed and systematically studied a cascaded bowtie photonic crystal nanobeam system that can achieve multiplexed long-range electrohydrodynamic transport and optical trapping of nanoscale particles. Ultra-high quality factor and ultra-low mode volume has been demonstrated, providing a strong field gradient ideal for trapping sub-20 nm particles. Combined with an applied alternating current electric field, the localized water absorption induces the electrothermal flow that can efficiently transport nanoparticles to the vicinity of a given bowtie region by switching the input wavelength. We envision this system will be promising in many fields, including single molecule characterization and assembly of single photon emitters.

The manipulation of micro- and nano-objects is of great technological significance to construct new materials, manipulate tiny amounts of liquids in fluidic systems, or detect minute concentrations of analytes. It is commonly approached by the generation of potential energy landscapes, for example, with optical fields. Here we show that strong hydrodynamic boundary flows enable the trapping and manipulation of nano-objects near surfaces. These thermo-osmotic flows are induced by modulating the van der Waals interaction at a solid-liquid interface with optically induced temperature fields. We use a thin gold film on a glass substrate to provide localized but reconfigurable point-like optical heating. Convergent boundary flows with velocities of tens of micrometres per second are observed and substantiated by a quantitative physical model. The hydrodynamic forces acting on suspended nanoparticles and attractive van der Waals or depletion induced forces enable precise positioning and guiding of the nanoparticles. Fast multiplexing of flow fields further provides the means for parallel manipulation of many nano-objects. Our findings have direct consequences for the field of plasmonic nano-tweezers as well as other thermo-plasmonic trapping schemes and pave the way for a general scheme of nanoscopic manipulation with boundary flows. [1] Fränzl, M. & Cichos, F. Hydrodynamic manipulation of nano-objects by optically induced thermo-osmotic flows. Nat Commun 13, 656 (2022).

We show that graphene nanoribbons (GNR) with tunable mid-infrared (MIR) plasmonic resonances can be utilized to form an electrically controlled plasmonic conveyor belt network to simultaneously and independently trap and transport multiple nanoscale objects with high performance. Furthermore, such a GNR plasmonic conveyor belt network can induce tunable bipolar (i.e., trapping or repulsive) optical gradient forces on nanoscale objects made of materials with strong permittivity dispersions in the MIR spectral region. The tunable bipolar optical forces can be exploited to achieve selective filtering, sorting and fractionation of nanoscale objects in a mixture based on their material compositions and/or microscopic structures.

Optical tweezers are extensively applied for numerous applications. However, optical tweezers are still subject to potential photo- and photothermal damages to fragile objects and are mostly used in fluidic environments. In this talk, I will present our recent research on developing novel optical techniques for the noninvasive trapping of objects and manipulating colloidal particles on solid substrates. These features will bring new possibilities in many fields, including biology, microelectronics, and nanophotonics.

Intracavity optical tweezers are a powerful tool to trap microparticles in water using the nonlinear feedback effect produced by the particle motion when it is trapped inside the laser cavity. In such systems two configurations are possible: a single-beam configuration and counterpropagating one. A removable isolator allows to switch between these configurations by suppressing one of the beams. Trapping a particle in the counterpropagating configuration, the measure of the optical power shows a feedback effect for each beam, that is present also when the two beams are misaligned and the trapped particle periodically jumps between them.

Lanthanide-based upconverting nanoparticles (UCNPs) boast low thermal sensitivity and brightness, which, along with the difficulty in controlling individual UCNP remotely, make them less than ideal nanothermometers at the single-particle level. In this work we show how these problems can be elegantly solved using a thermoresponsive polymeric coating. Upon decorating the surface of NaYF4:Er,Yb UCNPs with poly(N-isopropylacrylamide) (PNIPAM), a >10-fold enhancement in optical forces is observed, allowing stable trapping and manipulation of a single UCNP in the physiological temperature range (20-45 ºC). This optical force improvement is accompanied by a significant enhancement of the thermal sensitivity reaching a maximum value of 7 % °C-1 at 31.5 ºC caused by the temperature-induced collapse of PNIPAM.

Light-matter interaction in the context of optical trapping forms the fundamental basis for manipulating objects, enabling a plethora of exciting discoveries in many aspects of science and applications. To date, optical trapping has been explored exclusively on the interactions between electric field component of light and matter. Here we demonstrate the first magnetic optical trap in manipulating nano-objects in space. The potential created purely from magnetic component of light can selectively trap nanoparticles based on the optical magnetic susceptibility. Our work presents a new degree of freedom for studying fundamental light-matter interactions and nano-trapping and manipulation technologies.

Combining optical tweezers with acoustic trapping in one platform allows us to trap and manipulate sub-millimeter sized biological samples in suspension in a contact-less and flexible manner. The acoustic radiation forces levitate and trap the sample and steerable holographic optical tweezers give us an additional means of manipulation. We have implemented 3D acoustic trapping on a microfluidic chip, with three independent MHz transducers in three orthogonal directions; two side-transducers and one transparent top-transducer facilitating optical access for optical trapping and imaging. We can reorient the samples, or induce sustained rotations to gain access to multiple viewing angles of the object.

This conference presentation was prepared for the Optical Trapping and Optical Micromanipulation XIX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Optical Trapping and Optical Micromanipulation XIX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Optical Trapping and Optical Micromanipulation XIX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Optical Trapping and Optical Micromanipulation XIX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Optical Trapping and Optical Micromanipulation XIX conference at SPIE Optics + Photonics 2022.

This conference presentation was prepared for the Optical Trapping and Optical Micromanipulation XIX conference at SPIE Optics + Photonics 2022.