A High‐Performances Flexible Temperature Sensor Composed of Polyethyleneimine/Reduced Graphene Oxide Bilayer for Real‐Time Monitoring

Abstract

sensor with enough sensitivity, accuracy, and durability which can realize real-time and long-term temperature monitoring is strongly desired.To date, some researches on skinattachable temperature sensors were reported, in which different kinds of materials, including metal nanoparticles/ nanowires, [4,5] graphene, [6][7][8][9][10] carbon nanotubes (CNTs), [11][12][13] polymers (such as poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)), [5a,10,12,14] and others, have been explored as temperature sensing materials. Among various materials, graphene and its derivatives are wildly applied in temperature sensors owing to its outstanding electrical and thermal properties. [15] However, the sensitivities of bare graphene or its derivatives based temperature sensors are unsatisfactory and generally no more than 1.00% °C −1 . [6,7,9,16,17] In order to obtain superior sensitivity and flexibility of temperature sensor, graphene and its derivatives were composited with other materials, such as PEDOT:PSS, [10] polyurethane (PU), [18] CNTs, [19] polydimethylsiloxane (PDMS), [8b] and cellulose. [20] According to the studies of graphene composite temperature sensor, the maximum sensitivity can achieve ≈1.34% °C −1 , while the highest accuracy can only reach 0.2 °C, still existing a gap to monitor human skin temperature, and the linearity and durability still remain to be improved for the practical use. [18] Additionally, the fabrication complexity was also largely increased by the composite process.Herein, a skin-attachable flexible temperature sensor with high sensitivity and durability was developed on polyimide (PI) substrate through a facile spray-dipping method. The polyethyleneimine (PEI) and bare reduced graphene oxide (rGO) were used as the adhesive and temperature sensing material, respectively, without any composite involved. The spectroscopy properties of the sensing film were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), and X-ray photoelectron spectroscopy (XPS) and the morphology was obtained by scanning electron microscope (SEM). The sensor exhibited a high sensitivity of 1.30% °C −1 between 25 and 45 °C, which is closely approximate to the graphene composites temperature sensor. Specially, the sensor can detect the very tiny temperature change of 0.1 °C and showed excellent durability (120 d), satisfying the demands The temperature sensors are urgently required for real-time temperature monitoring in healthcare, disease diagnosis, and other areas. In this work, a skin-attachable flexible temperature sensor composed of polyethyleneimine/ reduced graphene oxide bilayer is developed on polyimide substrate by a facile spray-dipping process. The spectroscopy properties of sensing films are examined and analyzed in details and demonstrated the partial reduction of graphene oxide film. The prepared sensor exhibits high sensitivity (1.30% °C −1 ), linearity (R 2 = 0.999), accuracy (0.1 °C), and durability (60 d) for temperature sensing ...

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

“…For instance, continuous monitoring of the skin temperature in real time is important in predicting the cognitive status of the human body and thermal environments, as well as the early diagnosis of diseases. [ 5 ] Simultaneously, high stain sensitivity is a prerequisite for the accurate measurement of subtle human‐body‐induced deformations such as pulses and heartbeats to substantial deformations induced by joint motions. [ 6 ] In general, to meet the requirements of a multifunctional sensor for e‐skin, the sensitivity, stretchability, and acquisition of multiple stimuli without crosstalk are of paramount importance.…”

“…Such sensors using resistance temperature detectors generally employ metallic conductors such as platinum (Pt), [2] silver nanowires (AgNWs), [12] silver nanoparticles (AgNPs), [3] and graphene nanoplatelets (GNPs) on a flexible substrate. To date, different kinds of materials such as graphene and its derivatives (e.g., rGO and graphite) composited with PEDOT:PSS, [13,14] carbon nanotubes (CNTs), and cationic polymer (PEI) [5] have been explored for use in thermoresistive temperature sensors. The electrical and thermal properties of graphene oxide (GO) or even reduced graphene oxide (rGO) are different from those of pristine graphene because of structural defects or functional groups (e.g., COOH) or sometimes sp 3 -carbons do not convert to sp 2carbon.…”

Self‐Calibrated, Sensitive, and Flexible Temperature Sensor Based on 3D Chemically Modified Graphene Hydrogel

“…Recently, a variety of temperature transducing materials such as ultrathin metal elements, carbon nanotubes (CNTs), Si nanoribbons, conductive polymers, graphene, Ag nanocrystal, gels, and their composites have been developed to fabricate flexible temperature sensors with distinct sensing properties. [ 1–3,7–29 ] Furthermore, it is reported that chemical modification has significant impact on the sensitivity of some temperature sensing materials, such as Ag nanocrystal, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), hydrogel, etc. [ 16,22–26 ] Among various candidate materials, graphene and its derivatives have emerged as promising candidates for temperature sensing due to their extraordinary electrical and mechanical properties, such as one‐atom thickness, thermal and electrical conductivity, strong sensitivity to sample size, mechanical flexibility, etc.…”

Identifying human body states by using a flexible integrated sensor

“…Recent progress in flexible and wearable electronics has enhanced the possibility of continuous healthcare monitoring in daily life through the development of many kinds of wearable, conformable sensors [1][2][3][4][5][6][7][8][9][10] . These sensors mainly include flexible temperature sensors [11][12][13][14][15][16] , pressure/force sensors [17][18][19][20][21][22][23][24][25] , humidity sensors [26][27][28][29] , ultrasonic sensors 30,31 , optical sensors [32][33][34] , and biochemical sensors, but most are created to achieve noninvasive detection for a single vital indicator, such as body temperature (BT), heart rate (HR)/arterial pulse, blood pressure (BP), respiratory waves (RWs), or jugular venous pulse. To identify or diagnose human body states, multiple different vital indicators should be monitored continuously.…”