Transparent heaters (TH) have attracted intense attention from both scientific and industrial sectors due to the key role they play in many technologies, including smart windows, deicers, defoggers, displays, actuators, and sensors. While transparent conductive oxides have dominated the field for the past five decades, a new generation of THs based on nanomaterials has led to new paradigms in terms of applications and prospects in the past years. Here, the most recent developments and strategies to improve the properties, stability, and integration of these new THs are reviewed.

We report a family of monomers that are built from renewable resources and use the elimination of small molecules to access aliphatic polyesters, circumventing challenging monomer syntheses to make these functionalism polymers.

Owing to its high conductivity, good flexibility, low-cost, and ease of processing, poly(3,4-ethylenedioxythiophene) (PEDOT) has become a ubiquitous material, with uses in photovoltaics, energy storage devices, bioelectronics, thin film heaters, and thermoelectric devices. Although PEDOT is generally said to lack stability, very few studies dedicated to its degradation have been reported so far and corresponding mechanisms have not been fully elucidated. In this article, we report on the aging comparison under various conditions of three highly conductive PEDOT-based thin films differing by their counteranions. The effects of specific wavelength ranges (using high-pass optical filters), air and inert gas atmospheres as well as controlled moisture contents were monitored as a function of exposure time. Aging-induced alterations were analyzed by various characterization methods, including UV−vis−NIR spectroscopy, XPS, GIWAXS, and electrical conductivity measurements (down to 3 K). The exposure factors contributing most to degradation were different for each polymer film, indicating that the counteranions play a key role in stability. We highlight the strong impact of UV radiation on altering the structure of the conducting polymers, which in turn degrades electrical performance. Moreover, we propose a straightforward method to enhance stability and slow down the negative effects of aging using encapsulation within polyethylene naphthalate (PEN) thin films.

A careful control of the water content during PEDOT polymerization allow to reach extremely high electrical conductivity.

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The sun protection factor (SPF) is the most important quantity to characterize the performance of sunscreens. As the standard method for its determination is based on clinical trials involving irradiation of human volunteers, calculations of sunscreen performance have become quite popular to reduce the number of in vivo studies. Such simulations imply the calculation of UV transmittance of the sunscreen film using the amounts and spectroscopic properties of the UV absorbers employed, and presuppose the validity of the Beer-Lambert law. As sunscreen films on human skin can contain considerable concentrations of UV absorbers, it is questioned whether the Beer-Lambert law is still valid for these systems. The results of this work show that the validity of the Beer-Lambert law is still given at the high concentrations at which UV absorbers occur in sunscreen films on human skin.

For wearable applications such as electronic skin and biosensors, stretchable conductors are required (∼30% strain to follow the skin extension). Owing to its high conductivity, good flexibility, low cost, and ease of processing, poly­(3,4-ethylenedioxythiophene) (PEDOT) appears as a promising candidate. However, destructive cracks come out above 10% strain in the case of PEDOT:PSS, the most common form of PEDOT. Different strategies have already been investigated to solve this problem, including the design of specific structures or the addition of plasticizers. This article presents a different approach to obtain highly conductive and stretchable PEDOT materials based on doping with small counteranions. We indeed demonstrate the intrinsic stretchability (up to 30% strain) of thin films (35 nm) of PEDOT-based materials with small counterions. Both thin-PEDOT:OTf (triflate counter-ion) and thin-PEDOT:Sulf (sulfate counter-ion) films remain structurally resilient up to 25–30% strain, and their electrical conductivity remains remarkably stable over more than 100 cycles. Under limited strain (<30%), polarized UV–vis–NIR measurements (parallel and perpendicular to the stretching direction) show that the conductivity of the material is improved by chain alignment in the stretching direction. As a proof of concept, a thermotherapy patch is presented. It shows a fine temperature control (stability around 40 °C at 9 V bias) and a uniform heating across the surface.