Effect of unidirectional freezing using a thermal camera on polyvinyl (alcohol) for aligned porous cryogels

ABSTRACT

Unidirectional freeze casting for polymers and ceramics has been performed extensively; however, the mechanisms involved in unidirectional freezing are not thoroughly understood and therefore, in this study, polyvinyl (alcohol) hydrogels were freeze-thawed by unidirectional freezing and the resultant freezing profile was investigated using thermal imagery to comprehend the physical mechanism involved in the production of these aligned cryogels. The approach used follows a slight variation from what is currently used in literature, by enclosing the mould with insulating materials and leaving one side with a metal encasing for a fast freezing flow from the direction of the desired aligned of the structure. This method was cost-effective and simple; however, it was able to induce unidirectional freezing resulting in two distinct structures. These structures exhibited a cellular region interspersed with a fibrous and porous morphology. The method developed without the need of a freeze-dryer was confirmed to produce a unidirectional freezing which can be used for future studies.

KEYWORDS:

• Unidirectional-freezing
• freeze casting
• polyvinyl (alcohol) cryogels

Acknowledgments

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001 and Science Without Borders. We would also like to thank Patrick Doran - AIT for his valuable knowledge of the mould preparation and Larissa Nunes da Costa for the schematics.

Disclosure statement

No conflicts of interest regarding this manuscript.

Additional information

Funding

This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001; Science Without Borders – Finance Code 001.

Notes on contributors

Gabriel Goetten de Lima

Gabriel Goetten de Lima, have a degree in Physics from the Federal University of Paraná (2010) and a Master's degree in Mechanical Engineering from the Federal University of Paraná (2012), a full doctorate at the Athlone Institute of Technology funded by the DPE program - Full Doctorate Program abroad at CAPES. Has experience in Biomedical Engineering, with emphasis on Biomaterials and Biocompatible Materials. He is currently a postdoc researcher at Graduate Program in Materials Science and Engineering (PIPE) at the Federal University of Paraná.

Rêydila Rayenne Caminhas Barbosa

Rêydila Rayenne Caminhas Barbosa, visiting student at Athlone Insttitute of Technology from September 2015 to May 2016 in the program: Bachelor of Engineering (Honorous) in Mechanical Engineering. In Brazil, graduated from the Pontifical Catholic University of Minas Gerais in the Mechanical Engineering course, line of training in Mechatronics.

Mayara Pazin de Andrade Santos

Mayara Pazin de Andrade Santos, graduated in Science and Technology from the Federal University of ABC (2018). During his undergraduate degree, he held two years (2013 - 2014) of scientific initiation in the area of computer modeling as a CNPQ fellow. From June / 2015 to September / 2016, he participated in the Science Without Borders Program as a full scholarship holder at CAPES. During the program, he completed a 3-month full English course and took the third year of the undergraduate course “Mechanical Engineering and Renewable Energy“ at the Irish educational institution “Athlone Institute of Technology“, where he also helped in the development of this scientific research. Currently, she is a graduate student in Materials Engineering at Universidade Federal do ABC. He has been working since January 2018, as an Energy Efficiency Analyst at the company COMERC ESCO and SOLAR with the responsibility of assisting in the development and implementation of energy efficiency projects.

Bor Shin Chee

Bor Shin Chee, graduated in Biotechnology with expertise in microbiology, analytical technique, cell culturing, molecular biology, gene technology, bioprocess technology. My research interests include hydrogels, controlled drug delivery, wound healing, electrospinning and cell culturing. Presently, doing research on nanofibers using electrospinning technique for biomedical applications, with the aim to publish. Excellent proficiency in English, Malay and Mandarin. Postgraduate researcher in Polymer Engineering with experiences in hydrogel processing and characterisation since 2016. Working actively as a student supervisor and lab demonstrator in the Department of Life & Physical Sciences in Athlone Institute of Technology.

Washington Luiz Esteves Magalhães

Washington Luiz Esteves Magalhães, have a degree in Chemical Engineering at the Military Institute of Engineering (IME 1983), master's (1998) and doctorate (2002) in Materials Science and Engineering at the University of São Paulo. Is now a researcher at the Brazilian Agricultural Research Corporation and a position as the Head of Research and Development at Embrapa Florestas (2012-2013). He also conducted research as a visiting researcher at North Carolina State University (2008-2009) and at the University of Nottingham (2010). Washington also work as a collaborating professor in the Graduate Program in Materials Science and Engineering (PIPE) at the Federal University of Paraná and in the Graduate Program in Materials Science and Engineering at the State University of Ponta Grossa.

Declan M. Devine

Declan M. Devine, holds a PhD in Biopolymers Engineering (2006) from AIT, where he also completed graduate studies in polymer engineering. After his doctoral studies, he worked on a postdoctoral fellowship offered by the industry that allowed the development, patenting and licensing of polymeric films targeted for use in the ophthalmic industry for Transitions Optical Ltd. Dr. Devine was awarded a Marie Curie scholarship in 2012 and was named Irish champion of EU research (September 2012) and the Marie Curie fellow award of the week (October 2014). This work allowed Dr. Devine to receive training at world leading research centers, namely; Harvard Medical Schools Center for Advanced Orthopedic Studies and the Mayo Clinic Rehabilitation Medicine Center in the field of bone tissue engineering.

Michael J. D. Nugent

Michael J. D. Nugent Ph.D, is Lecturer in Engineering with over 22 years’ experience in material processing, material selection and material characterisation. Worked in industry in both Ireland and UK with industrial experience including medical device validation and quality engineering, project management, new product and process development and polymer processing. Background in polymer materials and processes, materials development, new product development and material analysis. Consultant to medical device and pharmaceutical industry. Research interests in hydrogels, wound healing, smart polymers, controlled drug delivery and polymer materials.