FIG. 4.

Non-biological molecular robots. (a) The operation of a continuous chemically fueled catenane rotary motor. The smaller ring (blue) travels clockwise around the larger ring (gray) when the fuel (red) is present. Reproduced with permission from Wilson et al., Nature 534(7606), 235–240 (2016). Copyright 2016 Springer Nature. (b) The operation of a molecular assembler. The molecular assembler produces four stereoisomers of a compound by different sequences of chemical addition and arm switching movements. Reproduced with permission from Kassem et al., Nature 549(7672), 374–378 (2017). Copyright 2017 Springer Nature.