BK - biophysics and complex systems

BK.OTM - Assembling an optical tweezers microscope

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Optical tweezers are a powerful tool to use the momentum of photons to grab particles, atoms, molecules, and living cells. Its invention was awarded the Nobel Prize in 2018, and optical tweezers are nowadays used in many laboratories for experiments ranging from pulling single molecules to even manipulating unicellular organisms. In our lab, we use optical tweezers to trap micron-sized particles inside cells, apply a force, and measure the particle displacement, thereby effectively ‘feeling’ inside a cell while it is fully alive. This allows us to perform mechanical measurements of parameters such as stiffness and viscosity on a subcellular scale. In this practical course, you will assemble and align an optical tweezers microscope and use it to capture and manipulate micron-sized particles. This setup can even be used to experimentally obtain a very fundamental constant in physics: the Boltzmann constant which we will then use to count the number of molecules in a mole by determining Avogadro’s constant.

III. Physik. Institut, F.03.126