Reconfigurable systems for multifunctional electronics

We report on measurements of the stiffness and breaking strength of monolayer MoS(2), a new semiconducting analogue of graphene. Single and bilayer MoS(2) is exfoliated from bulk and transferred to a substrate containing an array of microfabricated circular holes. The resulting suspended, free-standing membranes are deformed and eventually broken using an atomic force microscope. We find that the in-plane stiffness of monolayer MoS(2) is 180 ± 60 Nm(-1), corresponding to an effective Young's modulus of 270 ± 100 GPa, which is comparable to that of steel. Breaking occurs at an effective strain between 6 and 11% with the average breaking strength of 15 ± 3 Nm(-1) (23 GPa). The strength of strongest monolayer membranes is 11% of its Young's modulus, corresponding to the upper theoretical limit which indicates that the material can be highly crystalline and almost defect-free. Our results show that monolayer MoS(2) could be suitable for a variety of applications such as reinforcing elements in composites and for fabrication of flexible electronic devices.

We investigated propagation of light through a uniaxial photonic metamaterial composed of three-dimensional gold helices arranged on a two-dimensional square lattice. These nanostructures are fabricated via an approach based on direct laser writing into a positive-tone photoresist followed by electrochemical deposition of gold. For propagation of light along the helix axis, the structure blocks the circular polarization with the same handedness as the helices, whereas it transmits the other, for a frequency range exceeding one octave. The structure is scalable to other frequency ranges and can be used as a compact broadband circular polarizer.

We present the design for an absorbing metamaterial element with near unity absorbance. Our structure consists of two metamaterial resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a metamaterial absorber with a slightly lower predicted absorbance of 96%. This achieves a simulated full width at half maximum (FWHM) absorbance of 4% thus making this material ideal for imaging purposes. Unlike conventional absorbers, our metamaterial consists solely of metallic elements. The underlying substrate can therefore be chosen independently of the substrate's absorptive qualities and optimized for other parameters of interest. We detail the design and simulation process that led to our metamaterial, and our experiments demonstrate a peak absorbance greater than 88% at 11.5 GHz.