Abstract
Combining several methods for contact free micro-manipulation of small particles such as cells or micro-organisms provides the advantages of each method in a single setup. Optical tweezers, which employ focused laser beams, offer very precise and selective handling of single particles. On the other hand, acoustic trapping with wavelengths of about 1 mm allows the simultaneous trapping of many, comparatively large particles. With conventional approaches it is difficult to fully employ the strengths of each method due to the different experimental requirements. Here we present the combined optical and acoustic trapping of motile micro-organisms in a microfluidic environment, utilizing optical macro-tweezers, which offer a large field of view and working distance of several millimeters and therefore match the typical range of acoustic trapping. We characterize the acoustic trapping forces with the help of optically trapped particles and present several applications of the combined optical and acoustic trapping, such as manipulation of large (75 μm) particles and active particle sorting.
Highlights
Contact free trapping and micro-manipulation of small particles like cells or micro-organisms is a demanding task with many applications in physics, in analytical chemistry and in the life sciences
In the limit that the particle size is smaller than the sound wavelength, the exerted force scales with the volume of the trapped particle and enables the levitation of much larger particles against gravity compared to what is possible with optical forces alone
Acoustic trapping amends our optical trapping setup since it confines all particles within a specific plane, which is very convenient
Summary
Contact free trapping and micro-manipulation of small particles like cells or micro-organisms is a demanding task with many applications in physics, in analytical chemistry and in the life sciences. In this paper we present the simultaneous implementation of acoustic and optical trapping of living micro-organisms within a microfluidic environment. Both trapping methods are similar in the sense that they rely on radiation forces exerted by optical or acoustic fields, respectively. Optical trapping uses focused laser beams and offers a very precise and flexible way of handling individual small particles, but the comparatively weak optical forces are a limiting factor if one wants to scale this method for trapping of many or large particles. Acoustic trapping typically makes use of resonantly enhanced standing wave patterns, which depend on the probe chamber geometry This limits the flexibility of purely acoustic trapping. Our approach combines the high precision, selectivity and flexibility of optical forces with the large scale trapping abilities of acoustic forces
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
