Ballistic measurements using rotational optical tweezers determine the viscosity of fluids much faster than with conventional methods. They have the unique advantage of being calibration-free and using low laser powers that limit negative heating effects. This makes the technique ideal for performing ultrafast dynamic viscosity measurements in biological systems and will provide useful insight into the behaviour of dynamic environments.
Sculpted light provides a very flexible tool for the production of configurable and flexible confining potentials at the nano- and micro-scale. Sculpted light has been extensively used in diverse fields ranging from optical micromanipulation to quantum atom optics and quantum communication. It enables the production of complex optical potentials.
Optically driven nano and micromachines hold a promise of vast applications in interdisciplinary fields of science. These machines can be driven by versatile optical landscapes and provide applications ranging from microfluidics, drag delivery systems to complex biological systems.
Sculpted light refers to the generation of custom designed light fields. These light fields can be applied in many diverse fields ranging from interrogating single atoms or atom assembly to using these fields for optical micromanipulation and optical tweezers as well as creating new quantum devices and sensors. We consider here the study and application of light with structured intensity, polarization and phase. These sculpted lights can be used for intricate studies of light -matter interactions in a variety of environments. I will describe their use in transfer of transvers angular momentum of light and in studies of inertia.
Mechanobiology has become an important and ever-growing field of science that combines biology, engineering, chemistry and physics. It provides invaluable tool to studies of how the application of physical forces influences development, cell differentiation, physiology and disease. Many techniques have been developed throughout the time that enable these studies to contribute to our knowledge of complex biological systems. Optical or light technologies on the nano and micro-scale have enabled unprecedented advances in our understanding of mechanobiology. We will review the new developments in this rich field and point at further developments in this area that could lead to use of these nanotools to a further biomedical research community.
The inertial behaviour of a microscopic particle is obscured by its Brownian motion within a fluid. Collisions with fluid molecules give the particle velocity which dissipates on exceedingly short time scales due to the opposing drag forces from the fluid. Studying the motion at these very short time scales provides useful information about dynamic systems. In this work, we detail our approach to measure the angular velocity at these short time scales using Rotational Optical Tweezers enabling novel measurements of rotational dynamics and studying systems that are out of equilibrium.
We study far from equilibrium systems through investigating how groups of bacteria behave when other bacteria are present in the system and when barriers are introduced. For these studies we use structured light to fabricate microscopic structures for optical trapping and cell studies using two photon photopolymerization process. Structured light is created using spatial light modulator and correct for wavefront distortions in-situ providing aberration corrected system. This system is used to enable production of simple holographic optical tweezers apparatus with as many as 50 individual foci to create complex 3D microstructures. These structures can induce the collective behaviour of bacteria.
Light can transfer both linear and angular momentum to matter. This constitutes the principle of optical tweezers developed by Arthur Ashkin and can be used for three dimensional trapping and manipulation of objects in a large variety of systems. The optical tweezers can be used in combination with three dimensional structures produced using two photon photopolymerisation process (2PP) in order to provide a source of all optically driven mircomachines that in turn are used for dynamic studies of biological and physical processes. They can also be used to construct heat engines.
Making sense of the brain network and functions from individual neuronal activity is a challenging task. We developed a data analysis pipeline, combining unsupervised learning and supervised learning methods to reveal some of the intricacies of brain function in zebrafish. We were interested in particular to apply it to the senses of hearing, and balance. Using Optical Tweezers, we manipulated optically and individually each of the four ear stones which reside in the inner ear. Consequently, we simulated sound and acceleration in an alive zebrafish with laser beams. I will present the study of behaviour and neural responses to these stimulations.
Otoliths are calcium carbonate crystals located in fish ears. They play an important role in zebrafish for hearing, its sense of balance and acceleration. Many studies have been conducted to understand its structure, function but also development conditions. However the encoding in the brain as a movement sensor remains unknown. Here we developed a non-invasive system capable of manipulating one or two otoliths simultaneously in different directions to simulate movement or acceleration and sound. Our system uses optical traps created with an infra-red laser at different positions on the otoliths creating forces in chosen directions. However, as the optical traps need to go through brain tissue in a live fish, it becomes difficult to determine the exact forces applied. In this study we investigate the limits of forces determination. We will present the theory and experimental measurements of optical tweezers applied to otoliths which we mostly published in Nature Communications (doi:10.1038/s41467-017-00713-2). We will also present our latest result on brain imaging in response to artificial acceleration and sound.
Otoliths play an important role in Zebrafish in terms of hearing and sense of balance. Many studies have been conducted to understand its structure and function, however the encoding of its movement in the brain remains unknown. Here we developed a noninvasive system capable of manipulating the otolith using optical trapping while we image its behavioral response and brain activity. We’ll also present our tools for behavioral response detection and brain activity mapping.
Acceleration is sensed through movements of the otoliths in the inner ear. Because experimental manipulations involve movements, electrophysiology and fluorescence microscopy are difficult. As a result, the neural codes underlying acceleration sensation are poorly understood. We have developed a technique for optically trapping otoliths, allowing us to simulate acceleration in stationary larval zebrafish. By applying forces to the otoliths, we can elicit behavioral responses consistent with compensation for perceived acceleration. Since the animal is stationary, we can use calcium imaging in these animals’ brains to identify the functional circuits responsible for mediating responses to acceleration in natural settings.
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