Facile Phase Transition Measurements for Nanogram Level Liquid Samples Using Suspended Microchannel Resonators

We investigated phase transitions of a PEO-PPO-PEO triblock copolymer and n-heptadecane using a suspended microchannel resonator (SMR). After filling the microchannel of the SMR with each sample in liquid state, changes in the resonance frequency of the SMR were measured as a function of temperature, and then converted into changes in the density of each sample. As temperature increases, PEO-PPO-PEO unimers aggregate and form micelles (unimer-micelle transition), so the density of the polymer decreases and the resonance frequency of the SMR increases. As temperature decreases, n-heptadecane undergoes liquid to rotator phase (liquid-rotator transition), which increases the sample density and decreases the resonance frequency of the SMR. In addition, the liquid-rotator transition of n-heptadecane exhibits a sudden change in the quality factor of the SMR.