Herein we demonstrate the realization of a new technological concept, which enables the use of shape memory polymers (SMPs) as switchable information carriers. At first, we applied a surface-specific dyeing process based on 'guest-diffusion' on two sophisticated polymeric host materials, including a thermoplastic poly(ester urethane) SMP and a thermoset epoxy-based SMP. Upon drying, self-assembly of the dye molecules inside the polymer surfaces occurred, resulting in homogeneous color penetration depths of about 100 µm. Subsequently, the colored surfaces were patterned with quick response (QR) codes. For this purpose, laser ablation was used. The resulting cavity depth was exceeding the color penetration depth. This assured sufficient surface contrast and rendered the QR codes machine-readable. In a progressive approach, two thermo-mechanical functionalization protocols were designed in accordance with the thermal properties of the polymers. As a result of programming, the tag prototypes were converted into stable, temporary shapes with non-decodable QR code information. When thermally triggering the shape memory effect on the functionalized tags, we verified the mostly complete recovery of the polymer surface and the associated restoration into the almost original shape. As such, the QR code could again precisely be read out. We anticipate that tagging products with these information carriers is helpful for the purpose of secure one-time identification.
Here we present a suitable tag prototype with phasesegregated
poly(ester urethane) (PEU) as base material for
effectively switching a quick response (QR) code in its surface
from non-readable to readable. In comparison with recently
introduced tags (different geometry) we minimized the
thickness from plaque (2 mm) to foil size (0.5 mm) and reduced
the lateral QR code length from 15 to 5 mm. Subsequent to
surface-dyeing by means of guest diffusion, the QR code was
laser-engraved. The implementation of thermo-mechanical
functionalization via tensile deformation and cooling resulted in
the formation of stable shapes, which exceeded the barrier of
QR code readability at an elongation of 20%. Once
functionalized, tags were switched on demand by heating. As
such the recovery of the PEU was accomplished and the QR
code could again be read out. QR code carriers based on shape
memory polymer can be used in product and brand protection
applications.
Ein neu entwickeltes thermoplastisches Polyurethan (TPU) ist alles andere als „vergesslich". Formteile aus dem Material lassen sich in einer temporären Form fixieren und wieder nahezu in ihre ursprüngliche Gestalt zurückverwandeln. Dieser Formgedächtniseffekt hat gute Anwendungschancen - vom Marken- und Produktschutz über den Maschinen- und Automobilbau, bis hin zur Freizeit- und Spielzeugindustrie.
Auch Kunststoffe können sich erinnern. Das zeigt das Beispiel eines neuen thermoplastischen Polyurethans. Das Formgedächtnispolymer kann vorübergehend in einem deformierten Zustand fixiert und dann wieder nahezu in seine ursprüngliche Gestalt zurückverwandelt werden. Einsatzchancen hat es unter anderem im Markenschutz und Maschinenbau sowie in der Textil-, Sport-, Freizeit- und Spielzeugindustrie.
Mit Formgedächtnispolymeren auf Basis von TPU sind Bauteile spritzgieß- oder extrudierbar, die sich vorübergehend durch eine gezielte thermomechanische Behandlung in einer anderen temporären Form fixieren und stabilisieren lassen. Damit können Informationen gespeichert, vorübergehend sicher verschlüsselt und als Quick Response (QR)-Codes mit schaltbarer Lesbarkeit auf TPU-Etiketten eingraviert werden.
The surface of a shape memory poly(ester urethane)
(PEU) was either black- or blue-colored to obtain switchable
quick response (QR) codes after laser engraving and thermomechanical
functionalization (programming). The investigation
of dye and functional stability against UVA and hydrolytic
aging (at 23 and 60 °C) gave that contrast decline due to dye
decolorization (in case of UVA aging) or distinct dye diffusion
(in case of hydrolytic aging) finally inhibited the QR code
readability. By contrast, PEU as marked base material could be
adequately fixed and recovered even when the Michelson
contrast in the QR code region was falling in course of aging
below a crucial value of 0.1, whereupon the QR code was no
longer readable. Hence, we concluded that under the given
experimental conditions the decisive parameter for tag
applicability was the surface contrast.
The selective compression of quick response (QR) and Data Matrix code carriers based on shape memory polymer (SMP) with a freely configurable steel ball type indenter and adjacent thermo-mechanical shape fixing gave notched, room temperature (23 °C) stable, temporary shapes with non-decipherable codes. The microscopic investigation of cryomicrotome sections unveiled indentation-related shape fixities of about 90%. Independent of the selected two-dimensional code, the triggering of the SM effect resulted in sufficient shape recoveries to restore the code readability so that a maximum number of characters including 122 for a QR code (version 7) and 112 in case of a Data Matrix code (version 12) could be read with a scanning and decoding device. Due to the large number of difficult to copy shapes with on demand releasable information, SMPs may serve as viable information carriers for product and brand protection applications.
Following a guest diffusion approach, the surface of a shape memory poly(ester urethane) (PEU) was either black or blue colored. Bowtie-shaped quick response (QR) code carriers were then obtained from laser engraving and cutting, before thermo-mechanical functionalization (programming) was applied to stabilize the PEU in a thermo-responsive (switchable) state. The stability of the dye within the polymer surface and long-term functionality of the polymer were investigated against UVA and hydrolytic ageing. Spectrophotometric investigations verified UVA ageing-related color shifts from black to yellow-brownish and blue to petrol-greenish whereas hydrolytically aged samples changed from black to greenish and blue to light blue. In the case of UVA ageing, color changes were accompanied by dye decolorization, whereas hydrolytic ageing led to contrast declines due to dye diffusion. The Michelson contrast could be identified as an effective tool to follow ageing-related contrast changes between surface-dyed and laser-ablated (undyed) polymer regions. As soon as the Michelson contrast fell below a crucial value of 0.1 due to ageing, the QR code was no longer decipherable with a scanning device. Remarkably, the PEU information carrier base material could even then be adequately fixed and recovered. Hence, the surface contrast turned out to be the decisive parameter for QR code carrier applicability.
The selective compression of quick response (QR) and Data Matrix code carriers based on shape memory polymer (SMP) with a freely configurable steel ball type indenter and adjacent thermo-mechanical shape fixing gave notched, room temperature (23 °C) stable, temporary shapes with non-decipherable codes. The microscopic investigation of cryomicrotome sections unveiled indentation-related shape fixities of about 90 %. Independent of the selected two-dimensional code, the triggering of the SM effect resulted in sufficient shape recoveries to restore the code readability so that a maximum number of characters including 122 for a QR code (version 7) and 112 in case of a Data Matrix code (version 12) could be read with a scanning and decoding device. Due to the large number of difficult to copy shapes with on demand releasable information, SMPs may serve as viable information carriers for product and brand protection applications.