A compact electrothermal actuator includes a housing having a longitudinal axis. A set of particles for a collection of documents in a particular language is constructed from training documents such that a perplexity of the particle-based language model is substantially lower than the perplexity of a word-based language model constructed from the same training documents. Because there is no overlap between the adhesion layer and the bottom contact, the removal of adhesion layer is no longer necessary, leading to better contacts and simplifying the fabrication process.