A study on the thermal aging characteristics of an electro-osmotic pump using a liquid crystal polymer as a packaging material

The generation of bubbles due to the poor barrier property of packaging materials with regard to gas or water permeability can be detrimental to the performance and stability of electro-osmotic (EO) pumps, as their lifetime decreases with the increase in the bubble volume. Water vapor transmission rate tests were conducted on three different polymers, butyl rubber, polycarbonate, and liquid crystal polymer (LCP), to develop a suitable packaging material for EO pumps. LCP showed the most pronounced barrier performance for water vapor permeability before and after an accelerated thermal aging test. Field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and X-ray diffraction measurement were performed, and it was found that LCP had no significant microstructural, compositional, and crystallographic changes, and thermal degradation after the accelerated thermal aging test. An EO pump was assembled using LCP cases, and it was then tested under various aging temperatures (50 °C, 60 °C, 70 °C, and 80 °C). Moreover, the pump’s thermal aging characteristics were analyzed using the Arrhenius model. Based on the obtained results, the reaction rate constant ( k ) rapidly increased with the increase in the aging temperature, and the calculated value of the activation energy ( E a ) was 69.2 kJ/mol. Graphical abstract In electro-osmotic (EO) pumps, the generation of bubbles due to the poor barrier property of packaging materials when it comes to gas or water permeability can be very detrimental with regard to the performance and stability of the pumps, whose lifetime usually decreases with the increase in the bubble volume. In this study, aiming at solving the above-mentioned problems, we performed water vapor transmission rate (WVTR) tests on three different polymers, butyl rubber (BR), polycarbonate (PC), and liquid crystal polymer (LCP), so as to develop a suitable packaging material for EO pumps. Based on the tests performed on the EO pump built with LCP cases, LCP is found to be a very reliable and promising packaging material for EO pumps. Moreover, the pump’s thermal aging characteristics were analyzed using Arrhenius model.