Information entropy method for measuring the axial displacement of a bead and its application to analyzing the trapping force of optical trap

Jian Hua Bao; Yin Mei Li; Li Ren Lou; Zan Gong; Zhuo Wang; H. W. Wang

doi:10.1117/12.570866

8 February 2005 Information entropy method for measuring the axial displacement of a bead and its application to analyzing the trapping force of optical trap

Jian Hua Bao, Yin Mei Li, Li Ren Lou, Zan Gong, Zhuo Wang, H. W. Wang

Author Affiliations +

Proceedings Volume 5637, Electronic Imaging and Multimedia Technology IV; (2005) https://doi.org/10.1117/12.570866
Event: Photonics Asia, 2004, Beijing, China

Abstract

It is often necessary to follow the axial movement of a micron particle, such as the one trapped in optical trap, in addition to its radial movement. A new method based on the information entropy is developed for measuring the axial displacement, which is then used to reconsider the drag force method for measuring the radial trapping force and stiffness in an optical tweezers system. It is found that the new equilibrium position of the bead displaces not only radially but also axially when the surrounding viscous fluid flows at constant lateral velocity. The result implies that the trap stiffness measured in such a way is not really for the same horizontal plane. In addition, the measured trajectory of the bead (both radial and axial displacements) shows that the sphere escapes from the optical trap upward in stead of radially when the fluid velocity reaches the critical value. The fact indicates that the escape force is not the maximal radial trapping force as commonly accepted. It also deduced that the axial movement of the bead is one of error sources for trapping force calibration using the drag-force method.

Citation Download Citation

Jian Hua Bao, Yin Mei Li, Li Ren Lou, Zan Gong, Zhuo Wang, and H. W. Wang "Information entropy method for measuring the axial displacement of a bead and its application to analyzing the trapping force of optical trap", Proc. SPIE 5637, Electronic Imaging and Multimedia Technology IV, (8 February 2005); https://doi.org/10.1117/12.570866

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

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.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available