4D Printing of Smart Stimuli-Responsive Polymers

Raffaella Suriano,Marinella Levi,Roberto Bernasconi,Luca Magagnin

doi:10.1149/2.0411909jes

Raffaella Suriano, Marinella Levi + Show 2 more

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https://doi.org/10.1149/2.0411909jes

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Abstract

This paper starts with a short review of smart materials, which can be 4D printed and whose properties can be modified over time through specific stimuli such as heat, light, temperature, electric and magnetic fields. In the second part of the paper, a new polymer material for 4D printing was presented. The material was a thermally activated shape memory polymer (SPM), capable of memorizing a temporary shape and restoring the original one by means of a thermal stimulus. A self-healing behavior was introduced into the polymer, to enhance its durability and make it suitable for application in the fields of soft robotics and actuators. A polycaprolactone (PCL) was selected to provide a shape memory effect, taking into account its molecular weight and the possibility of chemically modifying it in order to make it photo-curable. Self-healing properties were provided by an ureidopyrimidinone (UPy) methacrylate monomer, capable of forming four hydrogen bonds with a self-complementary unit, favored by temperature. This new material was thus 4D printed by a digital liquid processing (DLP) printer. Both the shape memory effect and the self-healing feature were demonstrated, enabling this new material to be used as a raw material for new generation soft robotic actuators.

Highlights

The 4D printing concept was recently introduced to define the 3D printing of objects that are capable of changing their shape over time due to either a smart involvement of multiple materials in a single print or additive manufacturing of smart stimuli-responsive materials.[1,2,3] The incorporation of the fourth dimension into common 3D printing process is essential when printed components are able to switch between multiple configurations triggered by external stimuli, e.g. temperature, light, pressure, moisture, magnetic or electric field.[4]
Characterization of PCLDMA.—PCLDMA was analyzed through DSC in order to understand how the end-capping reaction influenced both the degree of crystallinity and the melting temperature of neat PCL
This result was expected because the methacrylate end groups introduced small defects and irregularities in PCLDMA chains, leading to a reduced degree of crystallinity and a decrease of crystallite dimensions, with a consequent reduction of the melting temperature

Summary

Introduction

The 4D printing concept was recently introduced to define the 3D printing of objects that are capable of changing their shape over time due to either a smart involvement of multiple materials in a single print or additive manufacturing of smart stimuli-responsive materials.[1,2,3] The incorporation of the fourth dimension into common 3D printing process is essential when printed components are able to switch between multiple configurations triggered by external stimuli, e.g. temperature, light, pressure, moisture, magnetic or electric field.[4]. A PCL dimethacrylate was selected as a photocurable SMP and selfhealing properties were provided by a methacrylate monomer with a 2-ureido-4[1H]-pyrimidinone functionality, due to its ability to form stable supramolecular interactions favored by heat.66 4D printing of this material was successfully achieved, opening the possibility to create customized complex geometries.

Results

Conclusion