Memory, switches, and logic gates through bistability in chemically fueled crystals

Abstract

The ability to store information in chemical reaction networks is essential for evolution, calculations, and, more generally, for the complex behavior, we associate with life. In biology, cellular memory is regulated through transcriptional states that are bistable, i.e., a state that can either be on or off and can be flipped from one to another through a transient signal. Such memory circuits have been realized synthetically through the rewiring of genetic systems in vivo or through the rational design of reaction networks based on DNA and highly evolved enzymes in vitro. Completely bottom-up analogs based on small molecules are rare and hard to design and thus represent a challenge for systems chemistry. In this work, we show that bistability can be designed from an extremely simple non-equilibrium reaction cycle that is coupled to crystallization. The crystals exert the necessary feedback on the reaction cycle required for the bistability resulting in an on-state with assemblies and an off-state without. We can switch the state on and off, such that each state represents volatile memory that can be stored in continuously stirred tank reactors indefinitely despite the fact that molecules are turned over on a minute-timescale. We showcase the system’s abilities by creating a matrix display that can store images and by performing Boolean logic by coupling several switches together.