Researchers produced a soft, mechanical metamaterial that can “think” about how forces are applied to it and respond via programmed reactions. The metamaterials feature flexible, conductive polymer networks that can compute all digital logic computations. The process creates decision-making functionality in engineered materials in a way that could support future soft, autonomous engineered systems that are invested with the basic elements of lifeforms yet are programmed to perform helpful services. These include helping maintain sustainable and robust infrastructure, monitoring of airborne and waterborne contaminants and pathogens, and assisting with patient wound healing.
Human thought processes are based on logic that is similar to Boolean logic from mathematics. This approach uses binary inputs to process binary control outputs — using only “on” and “off” sequences to represent all thought and cognition. The new soft materials “think” using the reconfiguration of the conductive polymer networks. Mechanical force, applied to the materials, connects and reconnects the network. Using a low-voltage input into the materials, the team created a way for the soft material to decide how to react according to the output voltage signal from the reconfigured conductive polymer network.
The type of logic used goes beyond pure mechanical logic, which is a way of using combinations of bistable switches — switches with two stable states — to represent the 0s and 1s of a binary number sequence. The team found that when they used pure mechanical logic, they ended up getting stuck because certain logical operations cannot be constructed.
The key to realizing all the logic gates was in the combination of the electrical polymer network with the soft, deformable material. The researchers created the logic operations by simultaneously reconfiguring the soft material and the electrically conductive network. This also ensures that the binary output is in the form of electricity, which is needed to drive an actuation mechanism that makes the material respond to the applied mechanical force. The combination of electrical and mechanical signals allows the machine to move to get out of the way or to push back in a certain direction.