Particles with internal structures of this sort may be of interest . Trapping experiments 2 carried out in water with spherical polystyrene particles have evidenced a lateral force, caused by the optical interaction of the particles, which tends to space them laterally at multiples of the wavelength. A single sheet with a square or hexagonal array of particles spaced by one wavelength can be expected to have favorable chracteristics if used as a mirror. More elaborate particle strutures, with different shapes such as needles or platelets, or multilayer structures, may also be considered. Amorphous or crystal particle structures may have different performance.
Macromolecular structures are equally of interest.
In the absence of damping action such as caused by water in the experiments just mentioned, the stability of a trapped sheet in vacuum has to be ensured otherwise. Passive cooling in the shadow of the umbrella tends to lower the temperature down to 30deg. The pellicle behaviour at the mirror's edge must also be investigated . Whether a continuous leakage, requiring refills, can be prevented is unclear . Techniques for preventing leakage should be explored.