Particle movement with squeezing flow of liquid films

The use of liquid chambers created with cover-slips on slides offers a very convenient means for particle and cell suspension handling. In this work, we demonstrate a simple approach of displacing suspended matter within such chambers by depressing one side of the cover-slip using piezoelectric translators to create a squeeze flow to move particles and to restore them close to their original position when translation ceased. In the system developed, the application of 60 V to a piezoelectric stack caused 60 μm of displacement. The transfer coefficient governing this ratio is largely dependent on the support stiffness in which we estimate here as k = 22,000 N/m. This value can be easily raised if required. The approach was also adapted to transfer particles and fluid between two cover-slip chambers sealed at all the edges except for a small air gap. During actuation, a liquid bridge was established between the two chambers to allow such transfer to occur. These findings constitute the first known successful attempt to use squeeze flow to manipulate particles.