Fig. 1.

Approximate timeline showing the emerging new milli/microrobot systems with their given overall size scale as significant milestones. (a) Implantable tiny permanent magnet steered by external electromagnetic coils [16]. (b) Alice 1 cm³ walking robot [17]. (c) In-pipe inspection crawling robot [18]. (d) Micromechanical flying insect robot [19]. (e) Screw-type surgical millirobot [20]. (f) Solar powered walking robot [21]. (g) Cardiac surface crawling medical robot [22]. (h) Bacteria-driven biohybrid microrobots [23]. (i) biohybrid magnetic microswimmer [24]. (j) Water strider robot [25]. (k) Hexapedal compliant walking robot [26]. (l) 12-legged crawling capsule robot [27]. (m) Snake-like medical robot [28]. (n) Magnetic bead driven by a Magnetic Resonance Imaging device in pig artery [29]. (o) MEMS electrostatic microrobot [30]. (p) Thermal laser-driven microrobot [31]. (q) Magnetically controlled bacteria [32]. (r) Crawling magnetic microrobot [33]. (s) Magnetic microswimmer inspired by bacterial flagella [34], [35]. (t) Flexible capsule endoscope with drug delivery mechanism [36]. (u) Programmable self-assembly of microrobots [37]. (v) Independent control of microrobot teams [38]. (w) Bubble microrobot [39]. (x) 3D magnetic microrobot control [40]. (y) Sperm-driven biohybrid microrobot [41]. (z) Catalytic microtubular [42]. (aa) Light-sail microrobot [43]. (ab) Bacteria swarms as microrobotic manipulation systems [44]. (ac) Swarm of mini-crawlers [45]. (ad) Free flight of micromechanical insect [46]. (ae) Undulating soft swimmer [47]. (af) Untethered pick-and-place microgripper [48]. (ag) Cell-laden gel assembling microrobot [49]. (ah) Multiflagellated swimmer [50].