Black Phosphorus@Laser‐Engraved Graphene Heterostructure‐Based Temperature–Strain Hybridized Sensor for Electronic‐Skin Applications

Abstract

Smart electronic skin (e‐skin) requires the easy incorporation of multifunctional sensors capable of mimicking skin‐like perception in response to external stimuli. However, efficient and reliable measurement of multiple parameters in a single functional device is limited by the sensor layout and choice of functional materials. The outstanding electrical properties of black phosphorus and laser‐engraved graphene (BP@LEG) demonstrates a new paradigm for a highly sensitive dual‐modal temperature and strain sensor platform to modulate e‐skin sensing functionality. Moreover, the unique hybridized sensor design enables efficient and accurate determination of each parameter without interfering with each other. The cationic polymer passivated BP@LEG composite material on polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene (SEBS) substrate outperforms as a positive temperature coefficient material, exhibiting a high thermal index of 8106 K (25–50 °C) with high strain sensitivity (i.e., gauge factor, GF) of up to 2765 (>19.2%), ultralow strain resolution of 0.023%, and longer durability (>18 400 cycles), satisfying the e‐skin requirements. Looking forward, this technique provides unique opportunities for broader applications, such as e‐skin, robotic appendages, and health monitoring technologies.

Recent Progress in Essential Functions of Soft Electronic Skin

“…[33] Alternatively, multifunctional sensors that can transduce each stimulus into separate signals can overcome these limitations. [279] Very recently, Chhetry et al [279] reported a skin-attachable temperature-strain multifunctional sensor by a black phosphorus and laser-engraved graphene (BP@LEG) heterostructure into an ultrathin, highly stretchable polymer substrate, as shown in Figure 22a. This multifunctional sensor exhibits remarkable temperature-dependent characteristics and linear microcrack propagation behavior, which are suitable for the thermoresistive sensor (Figure 22b,c) and strain sensor (Figure 22d,e), respectively.…”

“…e) Time-dependent resistance response of the sensor for seven consecutive cycles of strains from 2% to 20%. Reproduced with permission [279]. Copyright 2020, Wiley-VCH.…”

Rational Design of All Resistive Multifunctional Sensors with Stimulus Discriminability

“…First, the TS comprising a CNF550 film imparted a much larger variation in relative electrical resistance change (ΔR/R 0 ) for a given temperature rise than those made of CNF films prepared at higher CTs (Figure S3a, Supporting Information). The temperature coefficient of resistance (TCR) is a measure of the sensitivity of a resistive TS and is given by: [32,42] TCR / 100%…”

“…[20,22] Therefore, it is highly desired to develop sensitive multifunctional sensors having stimulus discriminability and yet benefiting from simple, cost-effective fabrication, and readout systems, for instance, a multifunctional sensor whose outputs are only given in electrical resistance signals. [30] However, such all resistive multifunctional sensors capable of stimulus discriminability have rarely been reported to date because conductive fillers, such as graphene, [31][32][33] carbon nanotubes, [34][35][36] and metal nanoparticles, [37][38][39] which are commonly used in the resistive PSs are known to exhibit significant sensitivity to temperature arising from their thermoresistive characteristics. [26,40] This paper is dedicated to developing flexible, all resistive multifunctional sensors which can simultaneously detect and discriminate temperature and pressure stimuli in real time, using carbon nanofiber (CNF) films as the sole sensing material.…”

Scalably Nanomanufactured Atomically Thin Materials‐Based Wearable Health Sensors

“…The temperature sensing ability of this Gr/SF/Ca 2+ ‐based temperature sensor was explored by attaching the sensor to a human hand. Chhetry et al [ 691 ] recently developed a resistive type temperature sensor based on BP and laser‐engraved graphene (BP@LEG). Park and colleagues addressed the ambient stability issue of BP by encapsulating the BP@LEG into an ultrathin flexible polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene (SEBS) substrate.…”