Robotic Fiber Fabrication based on Solidification Force Control

In this paper, we propose a robotic fiber fabrication method based on solidification force control to achieve highly repeatable mechanical properties of fibers. Dextran material is used as the specimen in the experiments. It has been chosen because of its similar rheological behavior to silk protein at high mass concentrations. However, the viscosity of dextran material is very low at its liquid phase, so force control during fabrication is challenging. Here, we propose a novel approach that controls the mechanical properties of fiber by controlling the solidification force. We employ impedance control with force tracking to control the solidification force to carry out the threading experiments and examine the benefits of the proposed approach. The repeatability of the mechanical properties of the fabricated fibers has been studied and compared using three scenarios a) fiber fabrication without solidification force control, abbreviated as FFNC, b) fiber fabrication with solidification force control after 60 seconds of solidification from the beginning of the solidification force detection abbreviated as FFWC, and c) fiber fabrication with solidification force control immediately after the detection of the solidification force, abbreviated as FFSC. The experimental results show that fibers fabricated using FFSC scenario have the highest repeatability based on the coefficient of variation of properties of the fabricated fibers, where the obtained coefficient of variation of the toughness, stiffness, elongation, and strength are 12.8%, 13.6%, 14.8%, 12.7% respectively. The experimental results also showed that fibers' mechanical properties toughness, stiffness, elongation, and strength have a negative correlation with the fabrication pulling velocity.