Tubular micromotors: from microjets to spermbots

Robotics and Biomimetics

Table 1 Comparative table of template-based electrodeposition and rolled-up nanotech as fabrication methods for tubular micromotors

	Template-based electrodeposition	Rolled-up nanotech
Required equipment	• Porous membranes as templates	• Photolithography
Required equipment	• Electrodeposition setup	• Thin film deposition setup
Suitable materials	• Conducting materials as outer layer	• Materials compatible with vacuum deposition
Advantages	• Easily accessible method	• Wide range of materials
	• Compact fabrication setup	• Fabrication of tubular structures with wide range of length and diameter possible
		• Fine control of layer thickness down to nanometer precision
		• Dynamic structures (stimuli-responsive microtubes)
		• Fixed tube array possible for mechanistic studies (i.e., bubble nucleation)
Limitations	• Tube shape preset by template pores	• Often requires vacuum deposition machine
	• Requires conductive outer layer
	• Release of tubes after dissolution of membrane

This table compares the two distinct fabrication methods for tubular micromotors according to the current state of the art. However, this might change in the future as the processes are optimized and developed further.