Highly Shrinkable Objects as Obtained from 4D Printing

Abstract

4D printing of shape memory polymers enables the production of thermoresponsive objects. In this contribution, a facile printing strategy is followed for an in-house synthesized thermoplastic poly(ether urethane). Processing by means of fused filament fabrication, in which the difference between nozzle temperature and material-specific glass transition temperature of the polymer is kept as low as possible, allows to obtain highly shrinkable objects whose shape and thermoresponsiveness can be precisely controlled. The effectiveness of the method also applies to the printing material polylactic acid. One possible application lies in highly shrinkable objects for assembly purposes. As proof-of-concept, lightweight hands-free door openers for healthcare applications are functionally simulated and developed. Once printed, such devices shrink when heated to fit on door handles, allowing an easy assembly. At the end-of-use, a heating-initiated disassembling and mechanical recycling are proposed. In perspective, a reuse of the materials in 4D printing can contribute to the emergence of a circular economy for such highly functional materials.

4D Printing: Technological and Manufacturing Renaissance

“…4DPed hands‐free door opener made from PEU assembly and its usage illustration (Reproduced with permission. [ 185 ] Copyright 2022, Wiley‐VCH GmbH).…”

“…This proposed methodology can be effectively used for developing consumer products. Similarly, Chalissery et al [185] produced highly shrinkable SMP-based materials through FFF process for developing lightweight handsfree door openers for healthcare applications. This 4DPed device shrinked when heated to fit on door handles, permitting an easy assembly as depicted in Figure 16.…”

Smart Mechanically Tunable Surfaces with Shape Memory Behavior and Wetting-Programmable Topography

“…In this way, an approach is pursued in which the so-called “If-Then-Else” relationships apply. Such approaches of self-sufficiently reacting material systems are currently being intensively researched in connection with programmable materials. − …”

Fused Filament Fabrication of Actuating Objects

“…[7] In the context of additive manufacturing (AM), the so-called "four-dimensional (4D)-printing" makes it possible to control the shape of an SMP both before and after heating above the DOI: 10.1002/mame.202200214 material-specific switching temperature. [8] This means that in certain cases the classic programming of the 1W SME can be omitted. In other words, 4D-printed objects are thermoresponsive and thus available for immediate use.…”

“…[13] Until recently, researchers focused on the implementation of thermoresponsiveness in objects with smaller layer heights (z < 5 mm), where the degree of shrinkage becomes weaker from layer to layer. [8,14] In a recent study, some of us employed an amorphous poly(ether urethane) and PLA for 4D-printing and showed that the technological key to realize distinct shrinkage is keeping the difference between the nozzle temperature and the glass transition temperature (T g ) of the polymers to a minimum possible value. This allows a rapid vitrification of the polymers once deposited on a printing bed.…”