Ink-jet printing allows non-contact dispensing of picoliter volumes of molten metals, adhesives, electro-active polymers, bioactive fluids, chemicals, optical polymers and more.  However, there is a lack of specific knowledge on preventing droplet motion on nonlevel surfaces and methods to detect and change drop volume to regulate fluid placement for desired line width. There are multiple main contributions in this research.

 

1) Model Derivation: Line Width of The Deposited Material on a Surface WRT Valve Duty Cycle and Contact Angle

 

 

A dynamic model of the line width as a function of changing duty cycle, nozzle velocity and the contact angle arising from chemical and physical properties of the liquid and surface. Using the duty cycle as input and the width as output, we can obtain control-affine dynamics.

 

2) Parameter Estimation and Tracking Control of  The Spread Line Width

Many terms in the dynamic equations are unknown or difficult to measure. Our approach simultaneously determines the cumulative uncertainties as a single parameter and provides control to regulate drop diameter. The net result is a closed-loop regulation of printed line width given no knowledge of the interactions between liquid and surface. Stability of the estimator and control law is established through Lyapunov analysis.

Printed lines width, from top to bottom the            desired widths are 3.0, 2.5, and 2.0mm

3) 3D Printer Nozzle Trajectory Planning On Quadric Surfaces

By applying surface parameterization and minimizing map distortion, we map designed patterns in 2D onto 3D
quadric surfaces.

 

Pattern Simulation (To pass through desired red points):

 

Pattern Deposition by 3D Printer

 

4) Robot End Effector  Pose\Trajectory Planning On Smooth Surfaces Based on Bezier Formulation

we apply Bezier spline surface parameterization, optimization and mapping distortion analysis
(based on Differential Geometry), to map a pattern onto a 3D surface with least possible distortion

Pattern Simulation and End Effector Frame in MATLAB

 

 

 

 

 

 

Rviz Simulation of The Robot Movement, Normal to The Surface During Deposition

 

Experiment of Pluronic Deposition on a Surface Using Staubli TX 90 Robot Arm, Syringe Pump and Depth Camera :

 

Application

One of our primary applications is automated wound treatment.  Callagen or other biologicals can provide structure to a wound, followed by seeding with cells to promomote healing.  A proof of concept can be seen below.

Papers describing this work include:

  1. B. H. Jafari, L. Namhyung, R. Thompson, J. Schellhorn, B. Antohe and N. Gans, “A Robot System for Automated Wound Filling with Jetted Materials,” Proc. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), October, 2018.
  2. B. Jafari, N. Lee, B. Antohe and N. Gans, “Parameter Estimation and Line Width Control of Robot Guided Inkjet Deposition,” Proc. American Controls Conference, June, 2018.

This material is based upon work supported by the National Science Foundation under Grant No. 1563424.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.