Convective flow reversal in self-powered enzyme micropumps

Area of Science:

• Biochemistry
• Fluid Dynamics
• Nanotechnology

Background:

• Surface-bound enzymes can function as pumps, driving fluid flow via catalysis.
• Enzymatic catalysis offers a potential intrinsic energy source for nano- and microfluidic devices.
• The precise mechanisms governing enzyme-driven fluid pumping remain incompletely understood.

Purpose of the Study:

• To investigate the spatiotemporal variations in pumping behavior of urease-based pumps.
• To elucidate the underlying mechanisms responsible for these dynamic pumping behaviors.
• To develop a theoretical model for chemical energy transduction into mechanical fluid flow.

Main Methods:

• Development of a theoretical model incorporating buoyancy effects from nonuniform substrate and product concentrations.
• Experimental validation of the theoretical model using urease-based pumps.
• Analysis of fluid flow dynamics, including speed and direction, in relation to enzyme activity, coverage, distance, and time.

Main Results:

• A theoretical model was developed predicting flow behavior based on substrate and product diffusivity and expansion coefficients.
• An unexpected flow direction reversal phenomenon was predicted and observed under specific diffusivity and expansion coefficient ratios.
• Experimental results confirmed that fluid pumping speed and direction are dependent on enzyme characteristics, distance from the pump, and temporal evolution.

Conclusions:

• The study uncovers novel spatiotemporal variations in enzyme-driven fluid pumping.
• Understanding these dynamics allows for the rational design of enzymatic pumps.
• These findings pave the way for effective, self-powered fluidic devices with controlled fluid flow.