For over a hundred years, calorimetry has been the method of choice for the investigation on thermodynamic properties. Conventional calorimetry, however, is limited to sample sizes of a few hundred milligrams and greater. To investigate the properties of the smallest of systems - on the order of nanometers - our group has developed a calorimetric technique with energy sensitivity of less than a nanojoule. MEMS fabrication methods allow us to create calorimeters that are sensitive to less than one nanogram of a deposited metal film, ten picograms of polymers and nanoliters of aqueous solutions.
Using our calorimetric technique, we have observed that nanoparticles melt at temperatures far below (ΔT > 100 K) the melting temperature of a bulk sample. Indium particles on the order of 1 nm in diameter can be fully liquid at room temperature! We have also observed that ensembles of "magic" nanostructures have discrete melting points which correlate well to increments in size of one atomic layer. Our group is also investigating the melting of isolated single crystals of polyethylene and liquid-phase chemistry in nanoliter sample sizes.