Stretchable Transparent Conductors: from Micro/Macromechanics to Applications

Abstract

electronics include stretchable solar cells, [2] stretchable organic light emitting diodes (OLEDs), [3] stretchable field-effect transistors (FETs), [4] stretchable supercapacitors, [5] stretchable actuators [6] and heaters, [7] etc. The emerging of stretchable electronics has foreseen the revolution of future electronics, ranging from design, shape and functions to installation, applications and even user experience. For example, stretchable optoelectronics, such as solar cells and OLEDs, are conformable, rollable and foldable. They can be installed on irregularly shaped roof or side walls of buildings, vehicles and other public utilities. Similarly, stretchable sensors used as e-skin can not only fit motions at joints of human or robots with tensile strain of large than 100%, [1e] but also sense signals related to strain, temperature, humidity and even blood pressure. [8] Moreover, the integration of different kinds of stretchable electronics may exhibit diversity in functions. [9] For instance, wearable devices of stretchable energy harvesting and storage electronics combining with stretchable sensors and heaters may sense the biomedical signal and keep the patient warm with the power collected from solar/friction energy. More potential applications of stretchable electronics in different fields, not restricted to the above examples, will be seen in the future.Stretchable transparent conductors (STCs) are fundamental components in stretchable electronics. They generally consist of a stretchable transparent polymeric substrate and a layer of conducting elements on or embedded in the substrate. The substrates involve poly(dimethyl siloxane) (PDMS) and polyacrylate-based elastomers [10] while the conducting elements include conducting polymers, [11] metal nanowires, [12] carbon nanotubes (CNTs), [13] graphene [14] or their hybrids. The substrates generally show transmittance of higher than 90% [15] and can be stretched to a strain of larger than 100%, e.g., PDMS and VHB (a typical acrylic elastomer) could exhibit a fracture tensile strain up to ≈160% [16] and several hundred percentages, [6a,17] respectively. STCs could be considered as the combination of transparent conductors and stretchable conductors; [18] they can simultaneously show stable conductivity and transparency upon deformation, including bending, folding, twisting, crumpling, stretching, etc. The transparency of STCs is attributed to the low attenuation of visible light by the substrate and the conducting layer. The conductivity is obtained due to the continuity of conducting layer either via uniform film or the connection of Stretchable transparent conductors (STCs), generally consisting of conducting networks and stretchable transparent elastomers, can maintain stable conductivity and transparency even at large tensile strain, beyond the reach of rigid/flexible transparent conductors. They are essential components in stretchable/wearable electronics for using on irregular 3D conformable surfaces and have attracted tremendous attention ...

In Situ Dynamic Manipulation of Graphene Strain Sensor with Drastically Sensing Performance Enhancement

“…The sliding process of graphene sheets can be divided into two parts: overlap stage and separation stage. [ 14,15 ] Cracks can be seen as the separation stage of the sliding, [ 16,17 ] which is the macroscopic expression of the sliding theory. The separation stage can be observed and analyzed by transmission electron microscopy (TEM).…”

Aligned Silver Nanowires Enabled Highly Stretchable and Transparent Electrodes with Unusual Conductive Property

“…Among these stretchable transparent conductive materials, metal nanowires‐based electrodes are intensively investigated because of the easy fabrication process and excellent electrical conductivity. However, the random metal nanowire nanostructures in these electrodes can give high junction resistance, electrical short‐circuits and leakages, and degraded conductivity at the stretched state, which hinder the performance of the electrodes . Therefore, we for the first time proposed a facile approach to layer‐by‐layer deposit the AgNWs onto prestrained flexible substrates with well‐controlled orientation.…”

Electrically tuning soft membranes to both a higher and a lower transparency

“…A volume of 25 µL of the PEDOT:PSS compound solution was used to spray on both sides of a 4-times pre-stretched VHB elastomer membrane a 28 mm-wide circular thin layer (estimated thickness lower than 100 nm), to be used as a transparent electrode. Then, the membrane was partially relaxed to a 3.5-times pre-stretch, making the PEDOT:PSS electrode wrinkled, due to the dissimilar stiffness with the elastomer membrane 45 . Then resulting −23.4% area strain corresponded to a reduction of the electrode diameter from 28 to 24.5 mm (Fig.…”