Shrinkable muscular crystal with chemical logic gates driven by external ion environment

Biomimetic chemical logic gates that can reversibly transform their shape and physical properties in response to their environment are an important research field. Most artificial chemical logic gates, however, rely on changes in the microscopic properties of molecules and ions in solution. Hence, developing chemical logic gates that influence macroscopic properties, such as crystal structures and magnetic and electrical properties, is essential for mimicking in vivo phenomena more accurately. Here, we develop a reset-set flip-flop circuit based on a single crystal that reversibly transforms in the presence of Ca2+ ions in aqueous solutions and is analogous to the chemical logic gate in muscles. During the crystal transformation, the lattice volume undergoes ~39% shrinkage, and the magnetic and electrical properties change considerably. Compared with existing products, the constructed crystalline system more closely resembles the function of actual muscles, which is promising for advancing the field of biomimetics. Biomimetic chemical logic gates transform in response to their environment but are currently focused on the microscopic properties. Here, a single crystal reset-set flip-flop circuit undergoes reversible volume shrinkage in response to ions in solution.