For a LM to be useful in a computing device, it has to have an appreciable lifetime. This is problematic for water based LM, as the gas permeability of LMs has previously been both established and exploited . As such, lifetime experiments were conducted on UHDPE LMs, Ni LMs, water droplets, and our new Ni/UHDPE hybrid LMs. Evaporation studies were conducted under ambient conditions, using 10.0 µl of DI water. UHDPE LMs were generated by rolling a droplet of water on a powder bed of UHDPE. Nickel LMs were made using a superhydrophobic surface (see above) to pre-form the droplet sphere, before rolling in an appropriate powder. A magnified view of both a Ni/UHDPE hybrid LM and a nickel LM can be seen in figure . From the data shown in table 1, it can be seen that both the nickel and UHDPE LMs have slower evaporation rates than a pure water droplet. This is expected, as the solid particles on the surface of the liquid form an (incomplete) barrier to evaporation. It also supports previous studies . Experiments also indicated that pure UHDPE LMs evaporate at a comparable rate to pure nickel LMs. This is due to a balancing act between the short narrow pores of the nickel LM, the long wide channels of the UHDPE LM, and the much larger contact angle of UHDPE compared to nickel . The larger grain size of the UHDPE creates longer channels for water vapour to traverse. This results in a smaller water vapour concentration gradient. It is noteworthy that the new hybrid LM offers the best protection, with the lowest rate of evaporation. It is suggested that this is due to differences in the nickel and UHDPE particle sizes. This difference is clearly visible in the magnified photograph shown in figure . The larger UHDPE particles offer good resistance to evaporation, due to their thickness. However, this also leads to large gaps between the particles, due to poor packing. This problem is alleviated by the nickel particles filling the available space. The use of two differently sized spheres for 3D spherical packing is well documented , and has been shown to increase the maximum perfect packing density beyond the 0.74 limit of a single-sized 3D sphere packing, to 0.93 for an ideal binary system . In this instance, due to the multilayer nature of the LM coating , it is more appropriate to relate to 3D sphere packing than 2D circle packing.