Nanopatterning of a Stimuli-Responsive Fluorescent Supramolecular Polymer by Thermal Scanning Probe Lithography

Abstract

The miniaturization of nanometer-sized multicolor fluorescent features is of continuous significance for counterfeit security features, data storage, and sensors. Recent advances in engineering of stimuli-responsive supramolecular polymeric materials that respond upon exposure to heat or mechanical force by changing their fluorescence characteristics open new opportunities as functional lithographic resists. Here, we demonstrate the patterning of a thermochromic supramolecular material by thermal scanning probe lithography (t-SPL), an emerging nanofabrication technique, which allows for ultrafast indentation with a heated probe, resulting in both fluorescent and topographic nanofeatures. t-SPL indentation reveals a linear relationship between the temperature at which material softening occurs and the indentation force in the range from 200 to 500 nN. The softening temperature decreases as the heating time increases from 4 μs to 1 ms, following time–temperature superposition behavior. Our results herein confirm that the fluorescence contrast, perceivable as a shift from red to green, was obtained by kinetic trapping of the dissociated state due to ultrarapid cooling when the probe is removed. We use t-SPL to create highly customized fluorescence patterns up to 40 × 40 μm2 in size with a spatial resolution of 86 nm and change the pitch size to modify the fluorescence intensity when observed by fluorescence microscopy. As an application, multifaceted security features with nanometer resolution are explored.

Thermal scanning probe lithography—a review

“…b Conversion of a functional material from a precursor 42,45,[86][87][88][89][90][91][92]94,95 . c Amorphization by short heating and fast subsequent quenching to obtain a less ordered phase 96,97 . d Local crystallization of an amorphous material 21,[98][99][100][101][102] .…”

Fabrication of Single‐Nanocrystal Arrays

“…f) Thermal SPL generated fluorescence pattern and corresponding AFM characterization. Adapted under the terms of the ACS AuthorChoice license . Copyright 2017, American Chemical Society.…”

“…Besides this, SPL can also induce intermolecular changes for patterning of materials other than semiconductors. Zimmermann et al reported the use of SPL to pattern fluorescent polymers by selectively quenching the fluorescent polymer with heat (Figure f) . These fluorescence patterns were used to write QR codes as shown in Figure f, and this concept can be easily extended to the nanoscale for generation of latent (hidden) optical features.…”

Emerging Scanning Probe–Based Setups for Advanced Nanoelectronic Research

“…The process of patterns' formation mainly relies on the strong contact force between the tip and the sample . ii) Thermal SPL (t‐SPL) : this technique uses a heating probe to alter the properties of the sample locally . iii) Thermochemical SPL (tc‐SPL) : this technique modifies the chemical properties of a material locally by heating; iv) Dip pen SPL (dp‐SPL) : this technique allows depositing of various types of molecules or inks on the surface of the samples .…”