Porous nanocarbon particles drive large magnitude and fast photomechanical actuators.

Better NIR (near infrared)-driven photomechanical actuation than reported for films containing carbon nanostructures such as carbon nanotubes and graphene has been achieved by incorporating porous carbon nanoparticles (PCNs) into single-layer films of polydimethylsiloxane (PDMS). The PCNs being obtained from a bio-waste source adds an exciting dimension to this work. The specific surface area (Asurf) of the pores, controlled using the pyrolization temperature and varying over a factor of 600 is seen to have a strong influence on the magnitude of the actuation as well as the time response of light-driven and relaxation processes. The quantity of the curing agent polymerizing the PDMS also has a notable role. The already significant actuation realized for single-layer films can be further enhanced (factor of two) by backing the PDMS film with an ultrathin gold layer. This addition, however, provides a novel way to control the direction of actuation, being opposite for the single and bilayer films. The mechanical properties obtained from stress versus strain measurements and the morphology of the films as imaged by electron microscopy, besides the coefficient of thermal expansion, have been employed to analyze the various observed behaviors. An important finding from the images is that the crystallinity of the PCNs plays a vital role in the magnitude of actuation: more the amorphous nature, larger is the actuation. Based on the results, which have much for bioengineering applications, a simple photo-stimulated LED switch is also presented. [ABSTRACT FROM AUTHOR]