Evanescent light field trapping and transport of micro- and nanocrystals of biological macromolecules on a waveguide for serial crystallography

• Main Author: Fuglerud, Silje Skeide
• Format: Dissertation
• Language: English
• Subjects: Fysikk og matematikk, Teknisk fysikk

A microfluidic evanescent field optical tweezer system was tested and developed for sample delivery of micro- and nanocrystals in serial crystallography. The fluid line was enforced, and the setup changed from vacuum pump-driven to syringe pump-driven. The pressure tolerance was found to be \SIrange{6}{10}{\bar} through repeated tests. Experiments with \SIrange{1}{2}{\um} polystyrene spheres and protein crystals showed that the system was able to trap micrometer-sized particles but that there were problems with sticking of especially protein crystals to the surface of the trapping region in the channel. Surface coating studies using cytop, \ac{PAH}, and \ac{BSA} were conducted. Cytop increased the cleanliness within the trapping region but did not change trapping behavior. \ac{PAH} decreased cleanliness in the trapping region and promoted sticking. \ac{BSA} adhered to the trapping region in a thin layer instead of the charged spheres tested and increased the ability of a charged sphere to move in the trap. However, the coatings did not provide a significant increase in trapping efficiency or the mobility of protein crystals (lysozyme, I3C, and thaumatin) tested. Decreasing the adhesion to the surface of the trap by modifying the crystallization protocol was also attempted but without success. The optical tweezers system tested in this thesis can not be directly applied in sample delivery in crystallography. Further studies and alterations are suggested, such as implementing a split waveguide with counter-propagating beams which can lift the particles some micrometers from the surface as demonstrated by Helle et al.