Page 107 - IJB-5-1

RESEARCH ARTICLE

Electrohydrodynamic printing process monitoring by

microscopic image identification

Jie Sun *, Linzhi Jing , Xiaotian Fan Xueying Gao , Yung C. Liang *
2,3
4
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3,4
4
1 Department of Industrial Design, Xi’an Jiaotong-Liverpool University, China
2 Departments of Food Science and Technology Programme, and Chemistry, National University of Singapore, Singapore
3 Advanced 3D Bioprinting Laboratory, National University of Singapore (Suzhou) Research Institute, China
4 Department of Electrical and Computer Engineering, National University of Singapore, Singapore
Abstract: Electrohydrodynamic printing (EHDP) is able to precisely manipulate the position, size, and morphology of
micro-/nano-fibers and fabricate high-resolution scaffolds using viscous biopolymer solutions. However, less attention has
been paid to the influence of EHDP jet characteristics and key process parameters on deposited fiber patterns. To ensure
the printing quality, it is very necessary to establish the relationship between the cone shapes and the stability of scaffold
fabrication process. In this work, we used a digital microscopic imaging technique to monitor EHDP cones during printing,
with subsequent image processing algorithms to extract related features, and a recognition algorithm to determine the
suitability of Taylor cones for EHDP scaffold fabrication. Based on the experimental data, it has been concluded that the
images of EHDP cone modes and the extracted features (centroid, jet diameter) are affected by their process parameters
such as nozzle-substrate distance, the applied voltage, and stage moving speed. A convolutional neural network is then
developed to classify these EHDP cone modes with the consideration of training time consumption and testing accuracy.
A control algorithm will be developed to regulate the process parameters at the next stage for effective scaffold fabrication.

Keywords: electrohydrodynamic jetting; convolutional neural network; image processing, scaffold fabrication
*Correspondence to: Jie Sun, Department of Industrial Design, Xi’an Jiaotong-Liverpool University, Suzhou - 215 123, China; Yung C. Liang,
Department of Electrical and Computer Engineering, National University of Singapore, 117 583, Singapore; chii@nus.edu.sg/jie.sun@xjtlu.edu.

Received: August 22, 2018; Accepted: October 16, 2018; Published Online: December 14, 2018
Citation: Sun J, Jing L, Fan X, Gao X, Liang YC, 2019, Electrohydrodynamic printing process monitoring by microscopic
image identification. Int J Bioprint, 5(1): 164. http://dx.doi.org/10.18063/ijb.v5i1.164

1. Introduction section . The printing resolution of EHDP is improved
[1]
by about two orders of magnitude in comparison to the
With the rapid development of micro-/nano- conventional inkjet printing systems . The deposited
[2]
manufacturing, electrohydrodynamic printing (EHDP)
has recently drawn great attention for its capability to fibers on the substrate can be orientated by a computer-
print micron to nanometer-scale fibers. EHDP technology controlled precision stage and stacked into scaffolds with
uses a pneumatic or syringe pump to supply viscous tailored microstructure. With the advantages of low cost,
solution to a nozzle with constant flow rate and applies a simple setup, and high printing resolution, EHDP has
high voltage between the nozzle and substrate to generate attracted a wide range of innovative explorations. Most
electric field. The solution is charged and distorted importantly, EHDP enables the fabrication of biomimetic
into a Taylor cone shape at the nozzle tip. When the fibrous scaffolds with the feature size close to the scale
electrostatic force exerted on the Taylor cone overcomes of extracellular matrix, which can facilitate the cell
[3]
its surface tension, a microjet ejects downward, quickly attachment, proliferation, and tissue regeneration .
solidifies due to solvent evaporation. The solidified fibers Even though the EHDP mechanism is conceptually
are deposited on the substrate with a nearly circular cross simple, the actual formation process strongly depends

Electrohydrodynamic printing process monitoring by microscopic image identification. © 2018 Sun J, et al. This is an open-access article distributed under
the terms of the Attribution-NonCommercial 4.0 International 4.0 (CC BY-NC 4.0), which permits all non-commercial use, distribution, and reproduction in
any medium, provided the original work is properly cited.
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