  Several designs for micro-devices for chemotaxis based on nano-motors are
proposed. The nano- or micro-motors are the conventional Janus rods or spheres
that are powered by the catalytic reaction of fuels such as hydrogen peroxide.
It is shown how these can be linked to make a device that can follow a
concentration gradient of the fuel. The feasibility of assembling the devices
using micromanipulation or metallic deposition is discussed. A possible design
principle is suggested for a device that follows the concentration gradient of
an analyte other than the fuel.
