Highly Conformable, Transparent Electrodes for Epidermal Electronics

Abstract

We present a highly conformable, stretchable, and transparent electrode for application in epidermal electronics based on polydimethylsiloxane (PDMS) and Ag nanowire (AgNW) networks. With the addition of a small amount of a commercially available nonionic surfactant, Triton X, PDMS became highly adhesive and mechanically compliant, key factors for the development of conformable and stretchable substrates. The polar functional groups present in Triton X interacted with the Pt catalyst present in the PDMS curing agent, thereby hindering the cross-linking reaction of PDMS and modulating the mechanical properties of the polymer. Due to the strong interactions that occur between the polar functional groups of Triton X and AgNWs, AgNWs were effectively embedded in the adhesive PDMS (a-PDMS) matrix, and the highly enhanced conformability, mechanical stretchability, and transparency of the a-PDMS matrix were maintained in the resulting AgNW-embedded a-PDMS matrix. Finally, wearable strain and electrocardiogram (ECG) sensors were fabricated from the AgNW-embedded a-PDMS. The a-PDMS-based strain and ECG sensors exhibited significantly improved sensing performances compared with those of the bare PDMS-based sensors because of the better stretchability and conformability to the skin of the former sensors.

A Compliant Ionic Adhesive Electrode with Ultralow Bioelectronic Impedance

“…Accordingly, to minimize the interfacial gaps to comply with skin for low impedance, decreasing the thickness and improving the adhesion provide effective approaches for dry and wet electrodes, respectively (Figure 1b; Tables S2 and S3, Supporting Information). [ 37,45–47 ] However, it remains a challenge to obtain lower bioelectronic impedance of dry electrode even when the thickness decreases to 100 nm. [ 16 ] For the wet electrode, achieving stronger adhesion between the conducting layer and skin is a key to eliminate the interfacial gaps.…”

Omnidirectional Strain‐Independent Organic Transistors Integrated onto an Elastomer Template with a Spontaneously Formed Fingerprint‐Mimicking Microtopography

“…[1][2][3][4] Such applications demand electronic devices with excellent mechanical flexibility, [5][6][7] good conformability, [8,9] ultralight weight, [10][11][12] and optical transparency under various types of external strain. [1][2][3][4] Such applications demand electronic devices with excellent mechanical flexibility, [5][6][7] good conformability, [8,9] ultralight weight, [10][11][12] and optical transparency under various types of external strain.…”

Nanofiber‐Reinforced Silver Nanowires Network as a Robust, Ultrathin, and Conformable Epidermal Electrode for Ambulatory Monitoring of Physiological Signals

“…Attributed to their excellent mechanical compliance, they could form fully conformal contact with the human epidermis, resulting not only in enhanced sensitivity but also in an unprecedented level of comfort regarding wearable devices . As a type of epidermal device, the conformal epidermal electrodes have been widely utilized for biometric sensing . Lu and coworkers reported a graphene‐based tattoo‐like epidermal electrode, which could be used to measure various physiological signals .…”

“…Despite these advancements, there are still considerable challenges for the development of epidermal electrodes. First, these electrodes are generally based on a layer of elastic polymer that acts as either a substrate or a matrix . To achieve tight and seamless contact with human skin that undergoes deformation, additional adhesives are normally required .…”

“…Although some recent reports have demonstrated that ultrathin electrodes can fully conform to human skin without extra adhesives, the robustness of the electrode has not been comprehensively proved. Moreover, most of the epidermal electrodes reported previously do not allow the penetration of gas as well as liquid, which poses a challenge for long‐time applications due to the evaporation of sweat. Therefore, it is greatly desirable to develop a highly robust, ultrathin, and conformable epidermal electrode.…”