Template-Assisted Preparation of Micrometric Suspended Membrane Lattices of Photoluminescent and Non-Photoluminescent Polymers by Capillarity-Driven Solvent Evaporation: Application to Microtagging

Giovanni Polito,Chiara Cozzi,Giuseppe Barillaro,Franco Cacialli,Valentina Robbiano

doi:10.1038/s41598-017-08278-2

Giovanni Polito, Chiara Cozzi + Show 3 more

Open Access

https://doi.org/10.1038/s41598-017-08278-2

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Abstract

In this work, the bottom-up template-assisted preparation of high-density lattices (up to 11 · 106 membranes/cm2) of suspended polymer membranes with micrometric size (in the order of few μm2) and sub-micrometric thickness (in the order of hundreds of nm) is demonstrated for both photoluminescent and non-photoluminescent polymers by capillarity-driven solvent evaporation. Solvent evaporation of low concentration polymer solutions drop-cast on an array of open-ended micropipes is shown to lead to polymer membrane formation at the inlet of the micropipes thanks to capillarity. The method is proven to be robust with high-yield (>98%) over large areas (1 cm2) and of general validity for both conjugated and non-conjugated polymers, e.g. poly(9,9-di-n-octylfluorene-alt-benzothiadiazole (F8BT), poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV), polystyrene (PS), thus breaking a new ground on the controlled preparation of polymer micro and nanostructures. Angle dependence and thermal stability of photoluminescence emission arising from F8BT membrane lattices was thorough investigated, highlighting a non-Lambertian photoluminescence emission of membrane lattices with respect to F8BT films. The method is eventually successfully applied to the preparation of both photoluminescent and non-photoluminescent micro Quick Response (μQR) codes using different polymers, i.e. F8BT, MDMO-PPV, PS, thus providing micrometric-sized taggants suitable for anti-counterfeiting applications.

Highlights

In this work, the bottom-up template-assisted preparation of high-density lattices of suspended polymer membranes with micrometric size and sub-micrometric thickness is demonstrated for both photoluminescent and non-photoluminescent polymers by capillarity-driven solvent evaporation
Since different polymer solutions were prepared using the same low-surface-tension solvent, no particular alterations either in terms of silicon wetting conditions or in terms of solvent evaporation rate arose from the use of different polymers, at least in the range of molecular weights and concentrations investigated
We argue that missing membranes in the μQR codes identify isolated closed-ended pipes within the network of open-ended pipes, highlighting a pattern-related localization of defects affecting μQR template fabrication with the microstructuring technique used in this work

Summary

Introduction

The bottom-up template-assisted preparation of high-density lattices (up to 11 · 106 membranes/cm2) of suspended polymer membranes with micrometric size (in the order of few μm2) and sub-micrometric thickness (in the order of hundreds of nm) is demonstrated for both photoluminescent and non-photoluminescent polymers by capillarity-driven solvent evaporation. Template-assisted formation of polymer membranes at the inlet of 2D arrays of micrometric-sized open-ended pipes is achieved by drop-casting of low concentration (~1 wt%) polymer solutions and subsequent capillarity-driven solvent evaporation at room temperature and atmospheric pressure.

Results

Conclusion