Light fastness, artificial sources

Light is an ideal source of energy to drive artificial molecular machines. First, it can be used to monitor the state of the machine using various spectroscopy techniques. Second, the response is very fast, even on nano- or picosecond scales. Third, photo-driven processes in such systems are usually reversible, resulting in photo-driven molecular machines having an autonomous operation that is very important for the construction of molecular devices. And last, photo-driven molecnlar machines are clean and convenient compared with chemically driven machines and... 

---