Humidity Controlled Micro Direct Ink Writing of Polymeric Bio-Ink for Drug Delivery and Bio-mimetic Tissue Synthesis

Primary Author: Kevin Estelle

Faculty Sponsor: Arda Gozen


Primary College/Unit: Voiland College of Engineering and Architecture

Category: Engineering and Environmental Science

Campus: Pullman




Principal topic

Bio-inks are biocompatible hydrogels and water-soluble polymers that are used to additively manufacture next-generation medical and pharmaceutical products. Through additive manufacturing, bio-inks loaded with biomaterials are extruded and assembled layer-by-layer to fabricate personalized artificial tissues and drug delivery vehicles. Success of such technologies relies on how precisely they mimic the complex microscale features of the native tissues, and there is a need to advance the current bio-printing technologies which do not possess this high manufacturing resolution. At lower size scales, the process suffers from rapid ink-drying and induced flow rate inconsistencies. This project can lead to more precise personalized drug delivery devices and artificial tissues.



We propose a novel bio-printing implementation where the humidity at the end of the extrusion nozzle is controlled to overcome such issues. A co-axial nozzle design is implemented where the inner nozzle is used to extrude the bio-inks and the outer nozzle dispenses water saturated air. This system increases the relative humidity up to 100% and beyond at the deposition site. The controlled humidity effects are observed through changes in volume flow rate, height, width, aspect ratio, and layer-to-layer cohesion and associated sidewall morphology obtained via imaging of the printed structures.



It is shown that the deposited material volume, ink spreading, and layer-to-layer fusion is a strong function of the humidity level at the end of the nozzle. With increasing humidity, stacked layers are more fused, the stackability remains intact, and clogging is prevented, which all increase the printability of bio-inks.