The effect of the printing temperature on 4D DLP printed pNIPAM hydrogels
Daphene Marques Solis, Aleksander Czekanski
Abstract
-isopropylacrylamide) (pNIPAM) stands out. pNIPAM presents exceptional characteristics such as a low critical solution temperature (LCST) close to the human physiological temperature and biocompatibility with several cell types. However, these characteristics are greatly affected by processing parameters. In this work, pNIPAM hydrogels were manufactured by AM using digital light processing; the printing temperature was varied between 5, 10 and 15 °C to analyze how it affects the hydrogels' final properties. The impact on hydrogels was analyzed by differential scanning calorimetry (DSC), swelling, deswelling and reswelling analyses, scanning electron microscopy (SEM) images, and compression tests. Based on our results increasing the production temperature of the hydrogels by 10 °C led to a decrease of more than 50% in the maximum swelling capacity, approximately 10% increase in water retention, and 6.5 °C variation in the LCST. The justification for such behaviour lies in the increase of the crosslinking rate and thickening of the external layer of hydrogels, which prevents the free movement of water from its interior.