ADDITIVE MANUFACTURING (AM) OF FLEXIBLE ELECTRONIC DEVICES: ONLINE MONITORING OF 3D LINE TOPOLOGY IN AEROSOL JET PRINTING PROCESS USING SHAPE-FROM-SHADING (SFS) IMAGE ANALYSIS

The goal of this work is online quality monitoring of flexible electronic devices made using Aerosol jet printing (AJP) additive manufacturing (AM) process. In pursuit of this goal, the objective is to recover and quantify the 3D topology of AJP-printed electronic traces (lines) through in situ images. The intent is to use the estimated 3D topology for online prediction of the device electrical performance characteristics. To realize this objective different shape-from-shading (SfS) techniques are tested to recover the 3D topology of lines from high resolution in situ 2D images. These images are obtained from a CCD camera installed on our experimental Optomec AJ300 AJP setup. White light interferometry is used offline to verify the online experimental trends. Three types of SfS algorithms are tested, namely, minimization method, Pentland's method, and Shah's method. Tests with synthetic images and experimental data indicate that Shah's method is more suitable. The correlation between online and offline estimates of line thickness was similar to 80%.