Robust Control Strategy of Fluid Dispensing Process for Solid Freeform Fabrication of Tissue Engineered Hydrogel Scaffold

A recognized approach in tissue engineering is the design of biocompatible and bioresorbable 3D scaffolds that can be used as templates for growing neo-tissues. Depending on the target tissue, a range of hydrogel polymers may be used to construct anatomically accurate scaffolds using three dimensional solid freeform fabrication approaches. This paper focuses on the modeling, simulation and preliminary experimental verification of a robust real-time control protocol for a positive displacement fluid dispensing process to be used in the fabrication of hydrogel scaffolds with specified feature sizes and controlled internal architecture. The actual fluid dispensing process can be characterized as a non-linear time-varying system with a high dependency on fluid properties, which are often unknown and inherently non-linear. To develop a control paradigm, an approximate analytical model is used to estimate the fully developed laminar flow of an unknown fluid through a cylindrical geometry. Experimental data is used offline to estimate the model coefficients. The initial estimated model is used to develop a control scheme for tuning the hydrogel flow through the deposition nozzle. The developed control strategy is then experimentally tested to investigate and quantify the performance capabilities of the fluid dispending process.