This thesis makes significant advances in the use of microspheres in optical traps as highly precise sensing platforms. While optically trapped microspheres have recently proven their dominance in aqueous and vacuum environments, achieving state-of-the-art measurements of miniscule forces and torques, their sensitivity to perturbations in air has remained relatively unexplored. This thesis shows that, by uniquely operating in air and measuring its thermally-fluctuating instantaneous velocity, an optically trapped microsphere is an ultra-sensitive probe of both mass and sound. The mass of the microsphere is determined with similar accuracy to competitive methods but in a fraction of the measurement time and all while maintaining thermal equilibrium, unlike alternative methods. As an acoustic transducer, the air-based microsphere is uniquely sensitive to the velocity of sound, as opposed to the pressure measured by a traditional microphone. By comparison to state-of-the-art commercially-available velocity and pressure sensors, including the world’s smallest measurement microphone, the microsphere sensing modality is shown to be both accurate and to have superior sensitivity at high frequencies. Applications for such high-frequency acoustic sensing include dosage monitoring in proton therapy for cancer and event discrimination in bubble chamber searches for dark matter. In addition to reporting these scientific results, the thesis is pedagogically organized to present the relevant history, theory, and technology in a straightforward way.

We are pleased to present “Optical Trapping and Manipulation: From Fundamentals to Applications”, a Special Issue of Micromachines dedicated to the latest research in optical trapping. In recognition of the broad impact of optical manipulation techniques across disciplines, this Special Issue collected contributions related to all aspects of optical trapping and manipulation. Both theoretical and experimental studies were welcome, and applications of optical manipulation methods in fields including (but not limited to) single molecule biophysics, cell biology, nanotechnology, atmospheric chemistry, and fundamental optics were particularly welcome in order to showcase the breadth of the current research. The Special Issue accepted diverse forms of contributions, including research papers, short communications, methods, and review articles representing the state-of-the-art in optical trapping.

Principles of Bacterial Detection: Biosensors, Recognition Receptors and Microsystems will cover the up-to-date biosensor technologies used for the detection of bacteria. Written by the world's most renowned and learned scientists each in their own area of expertise, Principles of Bacterial Detection: Biosensors, Recognition Receptors and Microsystems is the first title to cover this expanding research field.