Polymer filament–based in situ microrobot fabrication using magnetic guidance

Eric Diller,Zhe Li

doi:10.1177/1729881416682707

Abstract

In this article, we present a new three-dimensional printing inspired method for in situ fabrication of mobile magnetic microrobots with complex topology by bending a polymer filament on demand directly inside an enclosed operational environment. Compared with current microrobot fabrication methods that typically involve multiple microfabrication steps and complex equipment, the proposed method is simply and fast. The target shape is formed as the filament is fed through a hot needle inserted into the workspace, and the filament bending moment is induced by attaching a tip magnet at the end of the filament and projecting magnetic fields wirelessly from external electromagnetic coils. The filament bending mechanics and the behavior of the bending zone are analyzed and verified through bending experiment. A shape planner is developed for automatically controlling the fabrication process of any desired planar shapes, and the shape creation potential of this method is also studied. Magnetically active millimeter-scale robotic devices of different planar shapes are fabricated using polylactic acid filament with diameter as small as 100 μm. As demonstrations of the in situ formation of functional microrobotic devices, a micro-gripper is fabricated and controlled to assemble a cell cage. A micro-spring is created as a manipulating tool with force sensing capability. We, thus, show the utility of the fabrication method for creating complex microrobot shapes remotely in enclosed environments for advanced microrobotic applications, with the potential for scaled down applications in health care and microfluidics.

Highlights

The study of mobile magnetic robotic devices at millimeter and smaller scale has attracted recent interest due to their great potential in health care and micromanipulation.[1]
We show the fabrication of several complicated microrobotic shapes using 100–120 m polylactic acid (PLA) filament with high fabrication accuracy and demonstrate the removal of a fabricated microrobot from its confined workspace
It is one of the commonly used materials for 3-D printing. Another advantage of PLA over other thermoplastics is that it is derived from renewable resources and biodegradable, and not inclined to be harmful in bio-related applications. Other thermoplastics such as Acrylonitrile Butadiene Styrene (ABS) and nylon can be used for the fabrication based on different environment temperature requirements and applications

Summary

Introduction

The study of mobile magnetic robotic devices at millimeter and smaller scale has attracted recent interest due to their great potential in health care and micromanipulation.[1]. Plastic deformation will happen when its temperature is above the Tg, we can define lPDZ as the length of the filament from the tip of the needle to the point where the temperature just drops to Tg. to estimate lPDZ under different conditions and study their effect on the bending accuracy, it is essential to simulate the heat transfer along the filament. We can tell that the heat transfer equilibrium will be reached within 1–2 s and the final lPDZ is at the same order of magnitude as the filament diameter, suggesting sharp and accurate discrete bends when needles that match the filament size are used This suggests that the simulation results will not be affected by the infinitely long filament assumption when the filament length is longer than 0.8 mm for a 120 m diameter PLA filament. The minimum distance between any two parallel filament segments in a shape will be d

Results and discussion

Tip magnets 1 Tip magnet

Conclusion