Currently, the characterization techniques for hydrogels used in bioprinting are extensive, and they could provide data on the physical, chemical, and mechanical properties of hydrogels. While characterizing the hydrogels, the analysis of their printing properties is of great importance in the determination of their potential for bioprinting. The study of printing properties provides data on their capacity to reproduce biomimetic structures and maintain their integrity after the process, as it also relates them to the possible cell viability after the generation of the structures. Current hydrogel characterization techniques require expensive measuring instrument that is not readily available in many research groups. Therefore, it would be interesting to propose a methodology to characterize and compare the printability of different hydrogels in a fast, simple, reliable, and inexpensive way. The aim of this work is to propose a methodology for extrusion-based bioprinters that allows determining the printability of hydrogels that are going to be loaded with cells, by analyzing cell viability with the sessile drop method, molecular cohesion with the filament collapse test, adequate gelation with the quantitative evaluation of the gelation state, and printing precision with the printing grid test. The data obtained after performing this work allow the comparison of different hydrogels or different concentrations of the same hydrogel to determine which one has the most favorable properties to carry out bioprinting studies.

Three-dimensional bioprinting is a technology in constant development, mainly due to its extraordinary potential to revolutionize regenerative medicine. It allows fabrication through the additive deposition of biochemical products, biological materials, and living cells for the generation of structures in bioengineering. There are various techniques and biomaterials or bioinks that are suitable for bioprinting. Their rheological properties are directly related to the quality of these processes. In this study, alginate-based hydrogels were prepared using CaCl2 as ionic crosslinking agent. Their rheological behavior was studied, and simulations of the bioprinting processes under predetermined conditions were carried out, looking for possible relationships between the rheological parameters and the variables used in the bioprinting processes. A clear linear relationship was found between the extrusion pressure and the flow consistency index rheological parameter, k, and between the extrusion time and the flow behavior index rheological parameter, n. This would allow simplification of the repetitive processes currently applied to optimize the extrusion pressure and dispensing head displacement speed, thereby helping to reduce the time and material used as well as to optimize the required bioprinting results.

"Insanity is doing the same thing over and over again and expecting different results". This phrase, attributed to Albert Einstein, contains a message that sums up what is happening in education systems. Fortunately, an increasing number of "madmen" are choosing to do something different to "innovate" in the teaching-learning process. This paper shows the influence of innovating in four key aspects that influence learning: instruction, methodology, space and time, if we want to improve competence performance and start to make the objectives of the Bologna Declaration a reality, through experiences carried out in the School of Industrial Engineering (EII) of the University of Extremadura.

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