Analysis of the operating conditions of pulse electric field–assisted EHD for sodium alginate printing using design of experiment approach

Abstract

Electrohydrodynamic (EHD) printing is a novel printing technology with high printing resolution, making it suitable for applications such as tissue engineering and micro/nanomanufacturing. Inkjets from EHD fall on the substrate either in the continuous or drop-on-demand (D-O-D) mode. In this research, the D-O-D-based EHD printing process was used to print micro droplets of bioink assisted by a pulse electric field. A 2% (g/mL) sodium alginate solution was used as the bioink. A general full factorial design was used to analyze and observe the relation between the bioink droplet quality and the EHD process parameters. The diameter of the droplet, droplet generation rate, distance between two droplets, and the droplet consistency are the four major responses to evaluate the printing quality. The EHD process parameters, offset voltage, pulse width, and frequency, are the three regressor variables. After conducting the data analysis, it is observed that the higher frequency and the lower voltage produced the smaller droplet diameter, higher droplet generation rate, and nearer distance among the droplets. However, this increased the variance in the droplet patterns thus reducing the consistency of the printing process. It was also found that pulse width had marginal significance on the quality of printed drops. From the data analysis, four regression models were developed to aid in finding the parameter combinations to print 2% sodium alginate at a desired droplet diameter, droplet generation rate, and droplet distance. This proposed model can be used as a guideline for EHD bioprinting experimental setup, and it will significantly reduce the efforts to determine the optimal process parameters.