The method comprises contacting a silicon substrate with a silver salt and an acid for a time effective to produce spikes having a first end disposed on the silicon substrate and a second end extending away from the silicon substrate. The spikes have a second end diameter of about 10 nm to about 200 nm, a height of about 100 nm to 10 micrometers, and a density of about 10 to 100 per square microns. The nanostructures provide antimicrobial properties and can be transferred to the surface of various materials such as polymers.

An apparatus includes an optical writing module and an optical characterization module. The optical writing module is configured to emit a laser beam and guide the laser beam toward a substrate. The optical characterization module is optically coupled with the optical writing module such that the optical writing module and the optical characterization module share the same optical path. The optical writing module is configured to emitting an observation light beam toward the substrate. The optical characterization module is further configured to determine whether a mixture of solution and suspension is in contact with the substrate. When the mixture is determined in contact with the substrate, the laser beam is enabled to irradiate the mixture near a surface of the substrate, so as to form a mechanically rigid material deposition in contact with the substrate.

The method comprises contacting a silicon substrate with a silver salt and an acid for a time effective to produce spikes having a first end disposed on the silicon substrate and a second end extending away from the silicon substrate. The spikes have a second end diameter of about 10 nm to about 200 nm, a height of about 100 nm to 10 micrometers, and a density of about 10 to 100 per square microns. The nanostructures provide antimicrobial properties and can be transferred to the surface of various materials such as polymers.