Kwai S. Chan

Printed Carbon Nanotubes on Polymer Films for Active Origami

We describe a facile fabrication of solid-state actuators by coating common polymer films with a layer of carbon nanotubes. The composite material actuators are multifunctional energy transducers and were powered by heat, light, or electricity. The maximum observed force produced by an actuator was 60 times its own weight. Actuators were also demonstrated to bend more than 90°. The actuators were repeatedly activated for nearly 50,000 cycles without significant loss of performance for a sub-hertz actuator and 1,000,000 cycles in the case of a 30 Hz actuator. The utility of these devices was demonstrated by creating a walking robot.

Computational Design and Synthesis of Nitrogen-Substituted Carbon and Silicon Clathrates

A computational approach was utilized to design the framework and to identify potential guest atoms for stabilizing nitrogen-substituted carbon and silicon clathrates. Two new series of N-substituted carbon and silicon clathrates compounds were discovered as potential candidate materials. One of the hybrid C\bond N clathrates was successfully synthesized using an industrial arc-melting technique. The theoretical bulk moduli of these N-substituted carbon and silicon clathrates were computed and they are comparable to those of C3N4, Si3N4, and SiC. Some N-substituted carbon clathrates may be suitable for application as hard materials.

First-principles computational study of hydrogen storage in silicon clathrates

ABSTRACT Density functional theory (DFT) was utilized to compute the gravimetric capacity, volumetric capacity, and the binding energy of hydrogen molecules in silicon clathrates with guest (A) atoms such as Ba, Na, and Li, and framework substitutional atoms (M) such as C, Al, and Cu. The DFT computations show that these Type I intermetallic clathrates can accommodate a large number of hydrogen molecules, equivalent to 10 wt.%, and such hydrogenated structures, Ax(H2)nMySi46−y, occur with only a modest increase in lattice volume and a binding energy within the desirable range of 0.1–0.6 eV/H2 for hydrogen storage at or near ambient temperature. GRAPHICAL ABSTRACT IMPACT STATEMENT This paper identifies a number of Type I silicon clathrates that can accommodate large amounts of hydrogen molecules (10 wt.%) and may be suitable as hydrogen storage materials.