Closed-loop controlled conformal 3D printing on moving objects via tool-localized object position sensing

Abstract

The ability to functionalize and inspect moving objects is central to various emerging additive manufacturing (AM) applications, including in situ bioprinting and 3D printing in extreme conditions (e.g., space). This work provides a novel closed-loop controlled path planning method for planar and nonplanar microextrusion 3D printing on moving substrates and objects via real-time sensing of local object-tool offset that requires no description of the object's global geometry. Feedback control of the microextrusion nozzle z-axis position via real-time sensing of nozzle-surface offset using 1D laser displacement sensors enabled conformal 3D printing on moving substrates and objects. The method's utility was demonstrated by microextrusion 3D printing on planar substrates oscillating at the frequencies associated with tissue motion caused by human physiological processes, including respiration and the heartbeat. The method enabled conformal microextrusion 3D printing in the presence of substrate or object motion, including random vertical displacement (i.e., step changes) and continuous vibration (amplitude (A) = 0.8–6.7d, frequency (f) = 0.2, 0.4 and 1.3 Hz, where d is the nozzle diameter). The method was also validated by conformal microextrusion 3D printing on a human hand undergoing random vertical motion (A = 0–34.5d). This work advances closed-loop path planning for microextrusion 3D printing on moving substrates and objects. The created closed-loop path planning methodology and AM process may support various emerging AM applications, including in situ bioprinting and AM in mobile and extreme environments prone to mechanical disturbance, such as vehicles, vessels, aircraft, and spacecraft.