Sequential Motion of 4D Printed Photopolymers with Broad Glass Transition

Abstract

The term “4D printing” refers to the development of stimulus‐responsive structures through 3D printing of active smart materials, typically shape memory polymers. A noteworthy aim of this research field is to obtain objects able to display complex shape‐shifting motions, such as sequential transformations over time. In this work, this peculiar response is studied on a commercial photopolymer, printed by stereolithography and featuring, on the basis of its inherent broad glass transition, the so‐called “temperature‐memory effect” (TME). The TME, that is, a response in which the shape memory effect occurs on a region controlled by the deformation temperature, is studied in shape memory cycles where the deformation temperature is systematically varied, so to provide a correlation between deformation and recovery temperatures. This also allows to properly select two temperatures at which deforming a specimen along a multistep history, so as to finally separate each recovery process on the temperature and time scales. This sequential recovery is studied in double folded bars, with arms deformed at different temperatures, and on a properly designed self‐locking clamp. The obtained results are promising for the realization of smart temperature‐responsive structures printed with one single polymer and capable of multiple shape transformations.

Two-Way and Multiple-Way Shape Memory Polymers for Soft Robotics: An Overview

“…Yu et al [197] used the material under the name Gray 60 in the multi-material Polyjet 3D printer (Stratasys, Connex Object) material library, having a broad glass transition and exhibiting the multiple-way SME. More recently, Inverardi et al [198] used stereolitography to print multiple-way SMP structures. The effect was possible thanks to the broad glass transition of a commercial photopolymer, known under the name Clear FLGPCL02 and provided by Formlabs company.…”

Vat Photopolymerization 3D Printing of Advanced Soft Sensors and Actuators: From Architecture to Function

“…used a commercially available resin (Clear FLGPCL02) with a broad glass transition to realize a multiple and sequential recovery, and a self‐locking clamp was printed according to the triple shape changing effect of this SMP. [ 190 ] Based on that, grayscale DLP 3D printing for materials with widely tunable mechanical property gradients achieves the printing of multiple SMPs with heterostructure. Kuang et al.…”

3D printing of shape memory polymers

“…Instead of preparing own resins, Inverardi et al used a commercially available photoreactive resin (FLGPCL02), based on methacrylic acid esters and photoinitiator. 98 SLA printed cubes from this resin were compressed by 40% at different temperatures between room temperature and 120 C, cooled down and afterwards recovered well above the glass transition temperature. For all tests, full recovery was reached.…”