4D Printing of a Digital Shape Memory Polymer with Tunable High Performance

Abstract

Shape memory polymers (SMP) with 3D geometries and tunable shape-shifting behavior can open up new opportunities in intelligent devices. Achieving both simultaneously is difficult for conventional approaches. 4D printing allows fabrication of complex 3D SMP geometries that can change shapes (i.e., the fourth dimension is time), but tuning the shape memory response is challenging because of the printing constraints.Here, we report a material and process concept that allows digital light fabrication of SMP with fine control of not only the geometries but also the shape memory characteristics, within a printing time of 30 s. Digital light modulation allows spatio-temporal tuning of the material properties including shape memory transition temperature, rubbery modulus, and maximum elongation (up to 250%). Consequently, the process allows producing multiple-SMP within a single material construct using the same printing precursor. We demonstrate that this unique attribute is beneficial in constructing unusual shape-shifting 3D nano-photonic and electronic devices. The simplicity and versatility of our approach facilitates its future expansion into a wide range of geometrically complex devices with advanced functions.

A Material Combination Concept to Realize 4D Printed Products with Newly Emerging Property/Functionality

“…Qi et al pioneered the printed active composite materials [ 9,10 ] shifting into an intricate configuration directly by heating. Another important strategy is to use shape memory materials (SMM), [ 11 − 14 ] mainly including shape memory polymers (SMPs) [ 15 − 19 ] and shape memory alloys (SMAs) [ 20,21 ] in AM. As‐prepared products can change from their temporary structures to the initial configurations when exposed to a high temperature environment.…”

Review of Polymeric Materials in 4D Printing Biomedical Applications

“…Subsequent removal of the unreacted chemical agent would allow us have a polymer film and different structural shapes, while a difference in thickness allowed us to have in-built stress in the films. Release of stress from the films transformed the flat film into a 3D structure [36]. Figure 2B showed that the selection of planar light patterns allowed easy access to complex permanent shapes, which could be changed into temporary shapes and recovered upon reheating.…”

“…( b ) Digital fabrication of complex permanent shapes and proven of their shape memory behavior. In the planar print layouts, the black background represents no light exposure and the light and dark regions correspond to light exposure of 14 and 30 s, respectively [36]. Copyright (2019) American Chemical Society.…”

Multi-Material 3D Printed Shape Memory Polymer with Tunable Melting and Glass Transition Temperature Activated by Heat or Light

“…An important advantage is the ability to control the transition temperature of the material that is directly related to the control of the activation temperature. Tuning the transition temperature can be achieved in several ways: Mixing two different materials at various ratios [22], by controlling the degree of the SMP crosslinking [23][24][25] or; changing the type of crosslinking agent [19,25]. The first approach is suitable for Polyjet printing, in which the printer can print two different inks with controlled ratios at the same voxel.…”

“…The common technology for multi-material printing is Polyjet printing [18,22,27], however, a major limitation of this approach is the requirement to utilize only low-viscosity commercial materials. Another unique way for multi-material printing is vat polymerization, in which either, the exposure time of the material can be controlled locally, as presented by Zhang et al [23], or by replacing the vat during the printing process, as described by Ge et al [25]. Although, the local exposure approach is highly interesting, only one layer can be exposed, which limits the ability to form 3D objects.…”