Friday, February 19, 2016

PolySciTech P(NIPAM-Co-AM) (Polyvivo AO023) used for drop-on-demand (DOD) printing

PolySciTech division of Akina, Inc. (www.polyscitech.com) provides a wide array of thermogelling polymers including gels based of off poly(N-isopropylacrylamind-co-acrylamide) (AO023). One application of this is gel printing. Because it is possible to chill the printing head to dispense the cold liquid thermogel below the polymer LCST and then heat the receiver above the polymer LCST so the thermogel sets, there is the possibility to print gel structures. Eventually, this technology can allow for printing structures using thermogels which incorporate living cells into the printed component which could be used to generate living tissues. Recently, researchers at Purdue University utilized PNIPAM from Akina, along with a developed printing system to create a drop-on-demand system for studying the precise thermogel kinetics, dehydration parameters, and fluid-structure interactions for printing thermogels.  Read more: Han, Bumsoo, Gyu Young Yun, J. William Boley, Samuel Haidong Kim, Jun Young Hwang, George T-C. Chiu, and Kinam Park. "Dropwise gelation-dehydration kinetics during drop-on-demand printing of hydrogel-based materials." International Journal of Heat and Mass Transfer 97 (2016): 15-25. http://www.sciencedirect.com/science/article/pii/S0017931015310565

“Abstract: The present study aims to characterize and understand the dropwise gelation-dehydration phenomena during drop-on-demand (DOD) printing of hydrogel-based soft materials. Functional soft materials have broader impacts on many medical and engineering applications, but constructing soft materials into three-dimensional (3D) configuration with spatially varying properties is still extremely challenging. In order to establish a mechanistic understanding, a hypothesis was postulated that the porosity of hydrogel printed is determined by dropwise gelation and dehydration phenomena during the printing process. The underlying rationale is that many functional properties of the printed hydrogels are closely associated with the structural characteristics at the sub-droplet and droplet scales, specifically porosity. The porosity of a hydrogel droplet is thought to be determined by intra-droplet fluid–structure interactions during gelation and dehydration. In this study, thus, we characterized the gelation-dehydration and consequent microstructure of thermally responsive poly(N-isopropylacrylamind-co-acrylamide) (PNIPAM) copolymer droplets as a model hydrogel material. The gelation kinetics was studied by differential scanning calorimetry. Both macroscopic and microscopic structures of DOD printed hydrogels were characterized by a 3D profiler and scanning electron microscopy. Furthermore, a theoretical model to explain this complex transport processes was also developed. The results showed that the gelation is a rapid process and its impact is mainly observed at the deposition of droplets. Significant structural shrinkage of the printed hydrogel droplets was induced by dehydration. This shrinkage resulted in spatially varying intra-droplet porosity. A computational model of intra-droplet fluid–structure interactions was developed to explain this spatial variation of intra-droplet porosity. In addition, a new dimensionless parameter is proposed to gauge the significance of evaporation and interstitial water transport in the fluid–structure interactions. Significance of gelation kinetics, dehydration and complex fluid–structure interaction within the droplets was discussed to design a DOD printing process for 3D additive manufacturing of hydrogel-based soft materials. Keywords: Evaporation; Interstitial water transport; Dilatation; Fluid–structure interaction; Consolidation”
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