Orientation of swimming cells with annular beam optical tweezers

Abstract

A R T I C L E I N F OKeywords: optical trapping dual beam trap annular beams spatial light modulator dynamic orientation motile particles A B S T R A C TOptical tweezers are a versatile tool that can be used to manipulate small particles including both motile and non-motile bacteria and cells. The orientation of a non-spherical particle within a beam depends on the shape of the particle and the shape of the light field. By using multiple beams, sculpted light fields or dynamically changing beams, it is possible to control the orientation of certain particles. In this paper we discuss the orientation of the rod-shaped bacteria Escherichia coli (E. coli) using dynamically shifting annular beam optical tweezers. We begin with examples of different beams used for the orientation of rod-shaped particles. We discuss the differences between orientation of motile and non-motile particles, and explore annular beams and the circumstances when they may be beneficial for manipulation of non-spherical particles or cells. Using simulations we map out the trajectory the E. coli takes. Estimating the trap stiffness along the trajectory gives us an insight into how stable an intermediate rotation is with respect to the desired orientation. Using this method, we predict and experimentally verify the change in the orientation of motile E. coli from vertical to near-horizontal with only one intermediate step.The method is not specific to exploring the orientation of particles and could be easily extended to quantify the stability of an arbitrary particle trajectory.

Optical tweezers: theory and practice

“…Sculpting the shape of the wavefront and dynamically changing it allows to trap, move and control the orientation of non spherical particles. This was used by the group of Halina Rubinsztein-Dunlop to get important information on the properties of swimming cells [165]. The great advantage to held objects far away from surfaces can be combined with advanced imaging technique in addition the ability to rotate and orient trapped cells was used by Diekmann and colleagues to image cross sections of the cells under investigation that are impossible to achieve with conventional sample preparation and immobilisation [166].…”

Optical Tweezers Exploring Neuroscience

“…The number of traps is primarily limited by the available laser power and damage threshold for the beam shaping components, but with modern lasers it is possible to achieve 10 to 100 s of traps with either static or time-averaged configurations. Beams carrying orbital angular momentum ( Figure 3I) or spin angular momentum can be used to rotate particles (Simpson et al, 1997;Grier, 2003;Favre-Bulle et al, 2019), and structured light fields can be used to orient or stretch particles ( Figures 3F-J) (Bezryadina et al, 2016;Lenton I. C. D. et al, 2020a). If the devices used to generate these patterns are fast enough, beams can be dynamically scanned to create time averaged potentials or move particles around (Supplementary Video 1, Figure 3K).…”

Initiating revolutions for optical manipulation: the origins and applications of rotational dynamics of trapped particles

“…achieved using multiple independent parallel beams. As an example, a cylindrical particle can be held from opposite ends and be rotated around its own axis by changing the relative location of the traps [61,62] (Figure 2 (e)). Similarly, customised rotors [45], constellations made of several entities [45], and living cells [63] have been spun using an array of optical traps that held the objects from specially designed or naturally occurring handles, allowing, for example, the precision control on the microscale of fluid flows generated by the optically driven rotors.…”