Chemical control of Vorticella bioactuator using microfluidics

In this report, we demonstrate a microfluidic platform to control the stalk contraction and extension of Vorticella convallaria by changing concentration of Ca²⁺ with pneumatically-actuated elastomeric microvalves. Habitation, extraction and control of V. convallaria were carried out in a PDMS-based microfluidic device. By treating the cells with the permeant saponin, external actuation of cell-anchoring stalk between an extended and contracted state was achieved by cyclic exposure of the cells to a Ca²⁺ buffer (10^-6 M) and a rinse buffer containing EGTA as a chelation agent. When solutions were switched, the stalk contracted and extended responding to the ambient Ca²⁺ concentration change. The length of the stalk changed between 20 and 60 μm, resulting in a working distance of about 40 μm.