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(a)–(c) Bright-field images of dandelions with different shapes. (d)–(f) SEM images. Scale bars indicate 2 μm in each image.
Schematic representation of a holographic optical trapping system. A laser beam is imprinted with a computer-generated hologram by a diffractive optical element. The modified beam is relayed to an objective lens (that is also used for imaging) and is focused into the sample. The inset shows two dandelions trapped with two ring traps.
(a) Horizontal rotation rate (RPM—rounds per minute) as a function of ring radius with fixed winding number ( ). The inset illustrates a dandelion rotating about the optical axis in a ring trap. (b) Horizontal rotation rate as a function of winding number for a ring trap with fixed ring radius (R = 1.35 μm).
Vertical rotation rate as a function of distance between point trap and center of dandelion. Inset middle—Illustration of vertical rotation using a ring trap with no helical mode ( ) and a point trap as pedal. Inset upper right—Illustration of arbitrary rotation in 3D with a ring trap that has helicity ( ) and a point trap. Forces from individual traps are represented by blue arrows and the combined force with a red arrow (enhanced online). [URL: http://dx.doi.org/10.1063/1.4793401.1]doi: 10.1063/1.4793401.1.
Images acquired at 0.33 s intervals showing the upper dandelion that is rotated by a ring trap ( ) meshing with the lower dandelion that is held by a trap with no helicity ( ). The inset illustrates this arrangement (enhanced online). [URL: http://dx.doi.org/10.1063/1.4793401.2]doi: 10.1063/1.4793401.2.
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