Particles and cells often exist in the hydrated state. Hence, effective manipulation of particles and cells will require an ability to manage the fluid volume within.

One strategy that we have reported to accomplish collection is via capillary forces [1]. Capillary force mechanisms have the advantages of providing the motive force to move groups of particles to locations of interest while holding them in place, delicateness, and obviating the use external energy sources to drive the process. We show that a capillary force method based on simple coverslips that permits particles to be (a) hydrated constantly, (b) assembled, harvested, and assembled in batches using the same setup, and (c) assembled at different sizes and types at specific compositions (e.g. 40% of A, 60% of B). The physics behind the process is described and the technique demonstrated with the delivery and collection of 6 micron as a linear ensemble at the edge of meniscus.

The collection scheme was recently extended for use in laser pressure catapulting of adherent cells [2]. The laser catapulting was performed as a flow was introduced orthogonally. The moving cells terminate near the contact line within the liquid medium, ensuring that they remain continuously hydrated and where the surface tension forces hold them in place to permit a later collection process with a receptacle. By dislodging the cells close to the free edge of the liquid chamber, the amount of cell travel and thus contamination is minimized. The metrics of cell death and movement show that firing of the laser beam center a distance away from the cell to create a bubble that cavitates over time is more viable with the technique than directly on the cell.

The ability to observe samples undergoing controlled fluid flow under the microscope is important for studying biochemical processes and motion dynamics. We have developed a simple method [3] to achieve this using coverslips shaped using a fiber scribe. Testing showed good directional flow control within the test range of 0-1 ml/min flow rate and an ability to sustain a flow rate up to approximately 1 ml/min. Testing with a sealed T-channel coverslip demonstrated the ability to construct fluid network branches with this scheme. We also demonstrated the usefulness of this procedure in motion dynamic studies of Dunaliella algae swimming under fluid flow.

 

1. X. Lin, A. Neild, T.W. Ng, F. Shao, Continuous particle assembly in a capillary cell. Applied Physics Letters. 94 (2009) 034104.

2. A. Siddiqi, T.W. Ng, A. Neild Specific collection of adherent cells using laser release in a droplet driven capillary cell. Journal of Biomedical Optics. Accepted 12 October 2010.

3. BH-P Cheong, F Shao, TW Ng, A Neild, HY Tan Observation of dynamic samples using simple coverslip fluidics. Biotechnic and Histochemistry. doi:10.3109/10520291003597937.