Substrate-Controlled Bidirectional Pumping by a Bienzymatic Micropump

The development of autonomous, miniaturized pumps remains a problem of much interest, particularly with a view on microfluidics-based devices with increased portability and simplicity of use by nonspecialists. Spatially localized patches of enzyme imprinted on walls have been shown to induce a hydrodynamic flow when supplied with the corresponding enzyme substrate. Thus, such enzymatic micropumps are seen as a possible way of providing the means for nonmechanical, structurally simple, autonomous pumping. Hereby, we extend the current knowledge of enzymatic micropumps in two ways. First, we introduce β-glucosidase as an enzyme that facilitates building micropumps with robust inward flows in the presence of cellobiose (e.g., 2.51 ± 0.56 μm s^-1 in the presence of 80 mM cellobiose). Second, we embed β-glucosidase and urease within the same patch and thus obtain a bienzymatic micropump. The latter exhibits the so far missing capability of bidirectional pumping as it produces inward flows in the presence of cellobiose (e.g., 0.95 ± 0.37 μm s^-1 in the presence of 20 mM cellobiose) and outward flows in the presence of urea (e.g., 1.46 ± 0.47 μm s^-1 in the presence of 20 mM urea). This bienzymatic micropump is a significant step for the development of biocompatible micropumps with versatile, controlled, and on-demand hydrodynamic pumping capabilities.