Automating Optical Tweezers Experiments With a Microfluidic Laminar Flow Channel Device

Optical tweezers perform in singulo experiments on biological reactions that occur stochastically, often through multiple pathways. Characterization of single molecule trajectories allows determination of conformational distributions and detection of intermediates. However, this approach requires repeating the measurements tens or hundreds of times to achieve sufficient statistics. Aiming for high-throughput experiments, we combine microfluidic delivery of beads into the assay chamber with automated optical tweezers.We have developed a computer controlled microfluidic device for nano-litre sample-handling. Feedback control is achieved by monitoring and setting the pressure differences between individual inlet reservoirs and the outlet with high (<1 Pa, ca. 0.1 mmH2O) precision. This allowed us to achieve stable, repeatable, fluid flow in the micron-sized channels of a typical lab-on-chip setup.As a proof-of-principle experiment we performed repeated force-extension measurements on ∼10 kb dsDNA-molecules. Preliminary results on automatic assembly of the dumb-bell assay (bead-DNA-bead construct) and force-extension measurements will be presented. These automated, high-throughput, single-molecule experiments allow us to study rare events and phenomena in nanoscale biological physics, often inaccessible to other methods.