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.
Paulo Maia Neto, Luis Pires, Diney Ether, Ricardo Decca, Nathan Viana, Gert Ingold, Daniel Martinez, Yareni Ayala, Felipe Siqueira Rosa, Herch Moysés Nussenzveig, Stefan Umrath
We propose to use optical tweezers to probe the Casimir interaction between micro-spheres inside a liquid medium for geometric aspect ratios far beyond the validity of the widely employed proximity force approximation. This setup has the potential for revealing unprecedented features associated to the non-trivial role of the spherical curvatures. For a proof of concept, we measure femtonewton double-layer forces between polystyrene microspheres at distances above 400 nm by employing very soft optical tweezers, with stiffness of the order of fractions of a fN/nm. As a future application, we propose to tune the Casimir interaction between a metallic and a polystyrene microsphere in saline solution from attraction to repulsion by varying the salt concentration. With those materials, the screened Casimir interaction may have a larger magnitude than the unscreened one.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.