Externally Tunable, Low Power Electrostatic Control of Cell Adhesion with Nanometric High-k Dielectric Films

Biological systems are notoriously difficult to control. A major technical issue is controlling where and when bio-adhesion occurs on surfaces in engineered systems. Promoting bio-adhesion may be useful to pattern cells for tissue engineering. Preventing bio-adhesion is useful in micro-algal photobioreactors, where cleaning operations are costly and time consuming.<br/><br/>Current methods to promote or inhibit bio-adhesion depend on directly modifying the surface chemistry (e.g. hydrophobicity, molecular end groups). Here, we study the interaction between micro-algae cells (i.e. freshwater Chlorella vulgaris and saltwater Nannochloropsis oculata), and an engineered surface that can actively change its zeta potential based on the magnitude and polarity of applied voltage without changing its chemistry. Since the studied algae have negative zeta potentials, colloidal DLVO theory suggests that a surface with negative zeta potential should repel algae and a surface with positive zeta potential should attract algae. We observe that algae adhesion is inhibited at negative zeta potentials and enhanced at positive zeta potentials with a power draw of ~nW by applying -/+ 1V. Using microfluidic experiments, we report the effect of varying voltage magnitude, voltage polarity, wall shear, algae species, and solution salinity on bio-adhesion. We also conduct longer term (4 week) bio-adhesion and patterning experiments to observe the effect on practical performance