Optical Tweezers

1
Optical Tweezers

• Dielectric spheres trapped by tightly-focussed
  laser beam

Manipulate micron-sized materials, measure forces
Particle is trapped where gradient and scattering
forces balance
Adapted from M. Prentiss
2
Sphere is Pushed Towards Focus
Net force up
Net force down
Adapted from M. Prentiss
Net force left
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Tweezers Instrumentation
M. Prentiss
4
Optically-Controlled CollisionsAdhesion and
Infection

• Two optical traps to collide cell with
  virus-coated particle measure adhesion

Virus-coated microsphere
Red blood cell
Study adhesion as function of inhibitor colli
sion velocity osmotic stress other solution
conditions
5
Manipulation of Lipid Membranes Using Optical
Tweezers
flow
10 mm
10 mm
Solid lipid inclusions within initially spherical
vesicles were held in an optical trap while the
stage was translated, resulting in these
deformations of the liposome membrane.
6
Optical Trapping of Bacteria Encapsulated within
Vesicle