As portrayed in Figure 1a, in a robot, the control component is a circuit with a microcontroller, the energy supply comes from a battery or an energy harvester (e.g., photovoltaic cell), input and output are realized by antennas and sensors, and actuators allow for movement and operation. The incorporation of all these functions constitutes an intelligent robot capable of operating autonomously, sensing its environment and responding to it.

figure 1

Two distinct strategic approaches have been explored to develop small-scale robots.7 The first approach follows a top-down methodology, beginning with a range of miniaturized components such as tiny microcontrollers, sensors, and batteries, to ensure functional versatility, which are then integrated into a compact form.8,9,10,11,12,13 Alternatively, the bottom-up strategy starts with single-function components of minimal size and enhances their capabilities through the gradual addition of new parts. For example, intelligence was incorporated into a swimming microrobot14 by monolithic integration of sensors and complementary metal oxide semiconductor (CMOS).15 At the micro- and nanoscales, this approach delves into cutting-edge nanotechnologies to achieve sufficient intelligence, which includes mobility and locomotion,16,17 adaptability and flexibility,18,19 reconfigurability and programmability,20,21,22 multifunctionality and multimaterials,23,24 wireless power transfer and communication,14,25 as well as data processing and computing.15,26