Nanopropellers and their actuation in complex viscoelastic media

Area of Science:

• Biophysics
• Nanotechnology
• Biomaterials

Background:

• Biological fluids and tissues are complex viscoelastic media.
• Nanoporous macromolecular structures characterize these biological environments.
• Controlling nanoscale devices within these media presents significant challenges.

Purpose of the Study:

• To demonstrate controllable steering of helical nanopropellers in biological gels.
• To investigate the propulsion efficiency of sub-70 nm nanopropellers in viscoelastic fluids.
• To assess the potential of these nanopropellers for in vivo and intracellular applications.

Main Methods:

• Fabrication of helical nanopropellers with a filament diameter of approximately 70 nm.
• Actuation and tracking of nanopropellers in high-viscosity Newtonian and viscoelastic hyaluronan solutions.
• Comparison of propulsion velocities with larger micropropellers and theoretical predictions.

Main Results:

• Nanopropellers achieved propulsion in viscoelastic gels despite Brownian forces suppressing motion in pure water.
• Propulsion velocities in hyaluronan gels significantly exceeded those in Newtonian fluids.
• Enhanced speeds were observed when nanopropellers matched the mesh size of the viscoelastic gel.
• Nanopropellers demonstrated velocities comparable to larger micropropellers in high-viscosity solutions.

Conclusions:

• Helical nanopropellers offer a viable method for propulsion in complex biological viscoelastic media.
• The size of nanopropellers relative to the gel mesh size is critical for efficient propulsion.
• These nanopropellers show promise for applications in both extracellular environments and intracellular delivery.