Fig. 1.

The four increasing levels of smartness for biomaterials include inert, active, responsive, and autonomous. Inert biomaterials offer “merely” biocompatibility and do no harm, i.e., no toxic reaction in/to the body. Active biomaterials offer a one-way, uncontrolled release of therapeutics. Responsive biomaterials can sense specific signals found in the environment or biological processes to then release therapeutics. Autonomous biomaterials can sense a signal, release a specific payload, and adapt their properties to changing conditions to keep providing additional, advanced, and/or alternative forms of therapeutics