1. Plate mechanical metamaterials

Prof. Bargatin's group has pioneered new types of mechanical metamaterials that form robust plates out of ultrathin films. These are the thinnest plates one can handle with bare hands. These structures are extremely flat and thin (down to 35 nm), and weigh as little as 0.1 gram per square meter. Despite being made out of a brittle material (aluminum oxide), they are also remarkably robust, recovering their original shape after extreme bending deformations (see the series of photographs below or watch a video from our recent Nature Communications paper).

Another example of a plate mechanical metamaterial is provided by nanocardboard, a hollow plate with nanoscale thickness that offers the optimal scaling of stiffness with height and weight. Details can be found in another Nature Communications paper.

2. Photophoretic levitation

Photophoresis, a light-induced thermal transport and levitation mechanism, has been studied and used with micrometer-scale particles for over a century. In preliminary experiments, we demonstrated photophoretic levitation and propulsion of macroscopic (millimeter-scale) plates—1000's of times larger than ever before realized—paving the way for new technologies such as photophoretic unmanned air vehicles (UAVs). Nanoscale thickness of the used plate metamaterials rendered them lightweight enough to levitate, while their metamaterial design enabled both the needed thermal transport behavior and remarkable mechanical robustness. Please contact Prof. Bargatin if you'd like to find out more about this project.

3. Thermionic Energy Converters

With his collaborators, Prof. Bargatin's group has been developing MEMS-based prototypes of heat-to-electricity and solar-to-electricity energy converters that are based on evaporation of electrons from solid surfaces (thermionic effect). Such microfabricated thermionic energy converters (μ-TECs) can convert very high-temperature heat (>1000 C) directly to electricity. Microfabrication is the optimal manufacturing approach for thermionic energy converters because the optimal cathode–anode gap for TECs is in the range of 1–10 μm, which is highly suitable for MEMS-based fabrication processes. We have recently demonstrated a simple prototype of a mechanically and thermally robust encapsulated microfabricated thermionic energy converter (μ-TEC). The devices are fabricated out of silicon carbide and include barium-oxide coatings to reduce the work function. Small arrays of converters were encapsulated under a glass lid using wafer-scale anodic bonding.

For more detail, see Publications