Figure 5 . Horizontally printed beam used to create a 3D printed functional structure. (a) 3D printing of the horizontal beam. (b) The deflection-sensing horizontal beam with DIW deposited conductive path, scale bar = 10 mm. (c) Normalized resistance response to 0.4, 0.8, 1.2, 1.6, and 2.0 mm deflections over time. (d) Average peak height versus deflection cycling condition.
The plotted resistance shows peaks of increasing amplitude in the sensor signal corresponding to prescribed deformation. Indeed, the percent increase from peak to trough of the signal versus deflection shown in Figure 5d indicates a positive trend wherein Δ peak increases from 9.63% to 29.12% for δ = 0.4 and 0.8 mm, respectively. The trend continues finally to 52.74% at δ = 2.0 mm; thereby demonstrating the printed sensor’s potential to represent mechanical deformations in the structure. Based on these trends, this printed sensor has the potential to monitor deformations in a pre-existing structure in-situ, which could be invaluable in structural health monitoring applications.
4. Conclusions
In this work, we developed a versatile, reconfigurable DIW manufacturing method in tandem with a two-stage hybrid ink designed to facilitate fabrication of high-strength, self-supporting parts in unconventional printing spaces, such as underneath the build surface or horizontally. Our two-stage hybrid DIW ink combines a photopolymer and tough epoxy resin which is capable of autonomous curing under ambient temperature conditions, thereby creating complex, high-strength geometries without removal of the structure from the printing surface. The photopolymer component can be cured rapidly to enable layer-by-layer fabrication of complex structures. The photocured resin also possesses adequate adhesion to allow the fabrication of large volume structures on a diversity of substrates including acrylic, wood, glass, aluminum, and concrete. Moreover, the epoxy component cured after 72 hours in ambient, room-temperature conditions with increased adhesion strengths. We demonstrated the capabilities of the reconfigurable DIW extrusion nozzle method coupled with our developed ink by fabricating complex structures free of support structures in inverted and horizontal environments. In addition, via the addition of DIW-deposited conductive paths, we created a functional 3D printed structure capable of in-situ deformation monitoring. This work has the potential to be used for applications such as appending new parts to existing structures for increasing functionality, repair, and structure health monitoring.