A printable H-bonded cholesteric liquid crystal (CLC) polymer film has been fabricated that, after conversion to a hygroscopic polymer salt film, responds to temperature and humidity by changing its reflection color. Fast-responding humidity sensors have been made in which the reflection color changes between green and yellow depending on the relative humidity. The change in reflection band is a result of a change in helix pitch in the film due to absorption and desorption of water, resulting in swelling/deswelling of the film material. When the polymer salt was saturated with water, a red-reflecting film was obtained that can potentially act as a time/temperature integrator. Finally, the films were printed on a foil, showing the potential application of supramolecular CLC materials as low-cost, printable, battery-free optical sensors.

Self-assembled monolayers (SAMs) have received increasing attention since their introduction 30 years ago. Soon it was discovered that they can be used as alternative resist materials and are compatible with different established lithographic techniques commonly used in silicon semiconductor technology. Besides these possibilities to structure SAMs, other attractive properties emerged from the use of SAMs. E.g., the introduction of addressability into the patterns by selective functionalization with reactive precursor molecules and/or by applying suitable surface reactions was established. In this feature we highlight developments of photolithographic techniques that have been used in combination with SAMs serving either as resists for the patterning process or as precursor molecules for surface reactions, which can be performed on non-structured and mainly photochemically structured surfaces to obtain multifunctional surfaces with tunable surface properties. The aim is to provide an overview about the versatile possibilities to use silane based SAM systems to structure silicon-oxide substrates by introducing topographical as well as chemically heterogeneous surface structures. In particular the chemical activation of SAMs includes a large number of functionalization concepts which are intended to be summarized in this review. They will be introduced here according to the class of chemical reaction that has been used. Therefore, an introduction into the plethora of possible structures, which have been created by the combination of photolithographic structuring approaches, and the integration of tailor made surface functionalities into these systems will be highlighted. Additionally effective strategies to implement a diversity of chemical functionalities onto one substrate are summarized.

An optical and irreversible temperature sensor (e.g., a time-temperature integrator) is reported based on a mechanically embossed chiral-nematic polymer network. The polymer consists of a chemical and a physical (hydrogenbonded) network and has a refl ection band in the visible wavelength range. The sensors are produced by mechanical embossing at elevated temperatures. A relative large compressive deformation (up to 10%) is obtained inducing a shift to shorter wavelength of the refl ection band ( > 30 nm). After embossing, a temperature sensor is obtained that exhibits an irreversible optical response. A permanent color shift to longer wavelengths (red) is observed upon heating of the polymer material to temperatures above the glass transition temperature. It is illustrated that the observed permanent color shift is related to shape memory in the polymer material. The fi lms can be printed on a foil, thus showing that these sensors are potentially interesting as time-temperature integrators for applications in food and pharmaceutical products.

A printable hydrogen‐bonded cholesteric liquid crystal (CLC) polymer film is described, which can be used as a sensor for detection of gaseous trimethylamine (TMA). In this optical sensor the virgin CLC polymer network reflects green light. When anhydrous TMA gas penetrates the film, disruption of the hydrogen bonds occurs, with the simultaneous formation of carboxylate salts. The consequent reduction of the molecular order causes the green reflecting CLC film to become colorless. However, exposure to TMA in water‐saturated nitrogen gas results in a red reflecting film. Due to the hygroscopic nature of the polymer salt that is formed by TMA, water vapor which is present in the environment is absorbed by the films. This leads to swelling of the film, resulting in an increase in pitch size and therefore a red shift of the reflection band. Interestingly, after exposure to ambient conditions, restoration of the green reflecting film takes place, showing that the sensor can be used multiple times. In a proof of principle experiment, it was shown that these CLC films can be used as optical sensors to detect volatile amines, that are produced by decaying fish.

A fabrication process for multifunctional surfaces is designed leading to five different functional moieties (amine, thiol, carboxylic acid, fluoro, and methyl) being present on a single structured surface. The multifunctional surface is created by combining UV-ozone patterning, electro-oxidative lithography, the local deposition of self-assembled monolayers (SAMs), and surface modification schemes. Besides the characterization with conventional surface-sensitive techniques, the nature of the locally functionalized regions is demonstrated by self-assembly of three different probe nanomaterials (Si nanoparticles, Au nanoparticles, and hydroxyl functionalized micelles). A versatile fabrication approach for complex surfaces with addressable functionalities can be created, and it was possible to integrate five different functionalized areas on one substrate.