1. A.P. de Silva, H.Q.N. Gunaratne and C.P. McCoy, Nature 1993, 364, 421.
2. A. P. de Silva, Molecular Logic-based Computation, Royal Society of Chemistry, Cambridge, 2013.
3. See OPTI products at www.optimedical.com and VETSTAT products at www.idexx.com.
4. J. Ling, G.W. Naren, J. Kelly, T.S. Moody and A.P. de Silva, J. Am. Chem. Soc. 2015, 137, 3763.
5. J. Ling, G.W. Naren, J. Kelly, D.B. Fox and A.P. de Silva, Chem. Sci. 2015, 6, 4472.
6. S. Uchiyama, E. Fukatsu, G.D. McClean and A.P. de Silva, Angew. Chem. Int. Ed. 2016, 55, 768.
7. U.G. Reddy, J. Axthelm, P. Hoﬀmann, N. Taye, S. Gläser, H. Görls, S.L. Hopkins, W. Plass, U. Neugebauer, S. Bonnet, A. Schiller, J. Am. Chem. Soc. 2017, 139, 4991.
When we are well, how do we see? How do we draw? When we are ill, how do medical professionals look after us? The partial answers to questions like these arise from molecular logic gates. The first of these arose in Belfast when we recognized the similarities between semiconductor logic gates and chemical reactions.1,2 Fluorescent YES gates can monitor sodium levels in blood within millimeter-sized channels. These serve society by operating in hospital intensive care units and ambulances,3 and are the basis of a half-billion dollar industry. Other logic gate systems, akin to a full computer running a dedicated program, perform human-scale computations, e.g. edge detection of objects4 and outline drawing5 (Figure). More than 610 laboratories have contributed to this field so far. These nanometric gates can enter small inaccessible spaces,6 e.g. living cells,7 and send back raw or processed information. A short video on this topic is available at www.youtube.com/watch?v=sLGnZDP5Ecg