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Erscheinungsjahr
- 2012 (3)
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- Englisch (3)
Schlagworte
- Surface-specific dyeing (3) (entfernen)
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.
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.