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15th Workshop on Information Optics (WIO) (2016)

15th Workshop on Information Optics (WIO) (2016)

Two scientific articles form the 15th Workshop on Information Optics (WIO) (2016),  have been released:

Optical tweezers for force measurements and rheological studies on biological samples

and

Force measurement in the manipulation of complex samples with holographic optical tweezers

Both are related with the IMPETUX technology and good examples of its applications.

We invite you to have a look!

Optical tweezers for force measurements and rheological studies on biological samples

R. Bola, F. Català. M. Montes-Usategui, E. Martín-Badosa

imatge-reol-paperAbstract: Light allows the observation of the microscopic world but also, by means of optical tweezers, the non-invasive manipulation of micro-objects and the measurement of the forces exerted on them. However, measuring forces inside living cells is still a challenge due the characteristics of the trapped organelles (non-spherical, unknown size and index of refraction) and the cell cytoplasm surrounding them (heterogeneous and dynamic, non-purely viscous). Here, we show how two very recent methods overcome these limitations: on the one hand, forces can be measured in such environment by the direct detection of changes in the light momentum; on the other hand, an active-passive calibration technique provides both the stiffness of the optical trap as well as the local viscoelastic properties of the cell cytoplasm.

You will find the complete article here.

Force measurement in the manipulation of complex samples with holographic optical tweezers

Martín-Badosa, F. Català, J. Mas, M. Montes-Usategui,A. Farré, F. Marsà

imatge-paper-complexAbstract: Holographic optical tweezers are a powerful tool for the dynamic manipulation of micron-sized objects with light. The measurement of the forces exerted by the traps by direct detection of beam momentum is not restricted to spherical samples, viscous environments or the assumption of a harmonic trapping potential. Here, we demonstrate that forces on complex beams, such as a multiple trap system or a cogwheel beam, or samples such as cylinders, can be measured with this method. It also allows quantitative studies inside the cell, where molecular motors exert characteristic forces within a heterogeneous and viscoelastic medium such as the cytoplasm.

You will find the complete article here.

More news:

Fig. 1

Time dependence of trap position (top), force signal (middle) and Ca2+ fluorescence signal (bottom) recorded during a membrane tether pulling experiment. The force and Ca2+ ion channel activity signals exhibit negative correlation.

Fig. 2

Force and displacement data for two beads stimulated at frequencies of 4 Hz and 0.25 Hz. The progressive reduction of the beads displacement is in concomitancy with an increase of the applied force and loading rate.

Fig. 1

Schematic representation of the optical tweezers experiment. A fibronectin-coated bead is trapped, brought into contact with the cell membrane and stimulated with oscillations at different frequencies.

Fig.2

Time dependence of trap 1 and trap 2 position (top) and force (bottom) data along the different steps of the described dual tether pulling experiment.

Fig.1

Confocal video of the described dual tether pulling assay performed on a neuron axon. Courtesy of M. Krieg lab (ICFO).

Fig. 1

Time dependence of trap position (top), force signal (middle) and Ca2+ fluorescence signal (bottom) recorded during a membrane tether pulling experiment. The force and Ca2+ ion channel activity signals exhibit negative correlation.

Video 1

Confocal video showing a DVA neuron Ca2+ ion channel activity in a dynamic optical trapping assay. The pulling rate applied to the membrane tether is progressively increased. Scale bar = 5µm. Acquired at 10Hz.