Kumar Sumeet, Gunaseelan M, Vaippully Rahul, Kumar Amrendra, Ajith Mithun, Vaidya Gaurav, Dutta Soumya, Roy Basudev
Department of Physics, Indian Institute of Technology Madras, Chennai, 600036, India.
Department of Electrical Engineering, Indian Institute of Technology Madras, Chennai, 600036, India.
Biomed Opt Express. 2020 Jun 8;11(7):3555-3566. doi: 10.1364/BOE.392901. eCollection 2020 Jul 1.
3D pitch rotation of microparticles and cells assumes importance in a wide variety of applications in biology, physics, chemistry and medicine. Applications such as cell imaging and injection benefit from pitch-rotational manipulation. Generation of such motion in single beam optical tweezers has remained elusive due to the complexities of generating high enough ellipticity perpendicular to the direction of propagation. Further, trapping a perfectly spherical object at two locations and subsequent pitch rotation hasn't yet been demonstrated to be possible. Here, we use hexagonal-shaped upconverting particles and single cells trapped close to a gold-coated glass cover slip in a sample chamber to generate complete 360 degree and continuous pitch motion even with a single optical tweezer beam. The tweezers beam passing through the gold surface is partially absorbed and generates a hot-spot to produce circulatory convective flows in the vicinity which rotates the objects. The rotation rate can be controlled by the intensity of the laser light. Thus such a simple configuration can turn the particle in the pitch sense. The circulatory flows in this technique have a diameter of about 5 m which is smaller than those reported using acousto-fluidic techniques.
微粒和细胞的三维螺距旋转在生物学、物理学、化学和医学等众多应用中具有重要意义。细胞成像和注射等应用受益于螺距旋转操作。由于在垂直于传播方向上产生足够高椭圆率的复杂性，在单光束光镊中产生这种运动一直难以实现。此外，在两个位置捕获完美球形物体并随后进行螺距旋转尚未被证明是可行的。在此，我们使用六边形上转换粒子和捕获在样品室中靠近镀金玻璃盖玻片的单个细胞，即使使用单束光镊光束也能产生完整的360度连续螺距运动。穿过金表面的镊子光束被部分吸收并产生一个热点，在其附近产生循环对流，从而使物体旋转。旋转速率可通过激光强度控制。因此，这样一个简单的配置可以使粒子在螺距方向上转动。该技术中的循环流直径约为5微米，比使用声流体技术报道的直径要小。
