Stretchable π-conjugated polymer electrets for mechanoelectric generators

Abstract

Electrets are materials that retain quasi-permanent electric charges and are attracting attention as key components of batteryless micropower supplies. A chemical structure that facilitates ionization and that can stabilize these charges, such as a π-conjugated system, is expected to increase the charge density compared with that of conventional insulating polymers. Here, we report a mechanoelectric generator (MEG) (vibrational energy harvester) that uses alkylated π-conjugated polymers (Alk-CPs), which can be monopolarized either into positive or negative mode electrets. With the attachment of insulating, bulky, yet flexible alkyl side chains to the π-conjugated backbone, the poled Alk-CPs showed long charge lifetime suitable for MEGs. The elastic modulus of the electret was adjusted to approximately match that of the stretchable polyurethane substrate by blending two miscible Alk-CPs with different elastic moduli, producing a laminated film that could be stretched up to 300%. The MEG presented showed conformability when applied to a deformable object.

Quest for a Rational Molecular Design of Alkyl‐Distyrylbenzene Liquid by Substitution Pattern Modulation**

“…Diverse FMLs such as nanocarbon liquids, [3] luminescent liquids, [4] macrocyclic liquids, [5] and conjugated polymer fluids [6] have been developed in the past decade. Several alkyl‐π FMLs have been explored as substances on flexible/stretchable devices, such as microfluidic organic light emitting diodes (OLEDs) [7] and vibration‐powered electret generators [5a,6c] …”

A Stretchable Expanded Polytetrafluorethylene-Silicone Elastomer Composite Electret for Wearable Sensor

“…The combination of Ecoflex matrix and ePTFE gives rise to the improved comprehensive mechanical properties of the composite electret because of the excellent stretchability, low elastic modulus, and low hysteresis of Ecoflex elastomer ( Figure S5b,e ). In comparison with the recently reported research [ 5 , 6 , 9 , 17 , 20 , 22 , 26 ], the ePTFE/Ecoflex composite electret exhibits superior performance in terms of stretchability and longevity. Therefore, a composite electret with longevity, high charge density, and robust comprehensive mechanical properties is achieved, which can be potentially applicable to constructing self-powered flexible electronic devices.…”

“…Soft dielectrics such as elastomers bear sufficient stretchability but suffer short-lived charge [ 6 ]. Traditional electrets are difficult to meet the requirements for the rapidly developing flexible wearable devices, the stretchable and longevous electrets are intensively desirable and have been actively pursued [ 15 , 16 , 17 , 18 , 19 ]. Unfortunately, stretchability and longevity are usually mutually exclusive in the existing electrets.…”

Responsive molecular liquid materials

“…Reproduced under terms of the CC-BY license. [36] Copyright 2023, T. Nakanishi et al, published by Springer Nature Publishing AG. liquid (T g = −29°C, Figure 8d).…”

“…In addition, ionic liquids have ionic conductivity, and their application to electrochemical devices has been extensively studied, whereas FMLs have low polarity and can be applied to applications where conductivity is a hindrance, such as semiconductors [32][33][34] and electret devices. [35,36] Furthermore, the photostability of FML containing dye moieties was found to be approximately 10fold higher than the original unmodified dyes. [37] In contrast, the photostability of ionic liquids containing dye moieties has not been fully considered.…”