Until now you can have big elaborate robots or very small microbots but it is very difficult to have both. A blog post from New Scientist (where this video is from) points out the research on microbots, very small machines that will move, navigate and perform simple tasks. The ability to remotely power a microbot, thus eliminating the need for onboard battery or fuel, is already proven and one of the methods is the application of an AC field to a liquid where the robot is located. This microbot is essentially a diode, a one-way electric conductor. The different electric charges at its ends force the neighboring ions to move thus creating a small thrust that propels the bot. The team of Rachita Sharma and Orlin Velev from North Carolina State University developed a method where a controlled application of an additional DC field changes the ion distribution around the microbot and this time the ion field creates a torque that rotates the microbot. The DC field is applied until the completion of a 180-degree turn. Then the microbot moves again, now in the opposite direction. It is only 1.3mm long and as claimed by other scientists like Vesselin Paunov from the University of Hull, UK this arrangement can be further scaled down where it can be useful for diagnostic and localized drug supply applications.