The development of optical tweezers in single particle tracking with nanometer resolution and optical line tweezers with millimeter-scale trapping field

• Main Authors: Chang, Ai-Tang, 張愛堂
• Other Authors: Hsu, Long
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/pm7c3u

博士 === 國立交通大學 === 電子物理系所 === 101 === The techniques based on optical tweezers have become an important tool for the biologic research. At presently, there are two main developments of the optical tweezers technique. At first, the feature of the optical tweezers applies a linear restore force on the trapped particle. Thus, this feature combing a trapped particle tracking system is utilized to detect the target force. The other development is to enhance the attractive range of the optical force for manipulating cells to the specific positions or to form the specific maps. For a single particle system, a quadrant-photo diode (QPD) is usually utilized to track the trapped particle by measuring the forward or backward scattering light pattern of the trapping laser from the particle. This method is appropriate for the particle radius small than the trapping laser wavelength, only. Thus, we add an extra probe in the system to track a larger particle. With different sized particles, we investigate the optimized focal offsets between the probe and the trapping lasers experimentally and theoretically. The optimized focal offsets are a 3.3-fold radius ahead and 2.0-fold radius behind the trapping laser focus in the forward and the backward tracking configurations, respectively. These two configurations not only enhance the QPD signal sensitivity but also enlarge the tracking range of the particle position obviously. To expand the attractive range of the optical force, we also design a cylindrical mirror chip with a PDMS immersion layer to form a millimeter-sized optical line segment and a 30 □m longitude spherical aberration. 10 μm-in-diameter particles are attracted by this light pattern at different layers in a 40-□m-height fluidic channel and arranged a line on the top surface of the fluidic channel. Additionally, The particles move along the optical line segment stably with the velocity less than 58 □m/sec and the incident angle is 34。. This cost-effective and large-scale optical line guiding can be achieved in our design.