Ultra-sensitive and durable strain sensor with sandwich structure and excellent anti-interference ability for wearable electronic skins
Graphical abstract
Introduction
With the development of multifarious smart terminals, flexible sensors have aroused enormous research interests in the wide application of wearable electronic skins [1,2], soft robotics [3], human motion monitoring [4], human-machine interfaces [5,6] and artificial intelligence [7]. Among them, stretchable strain sensor with favorable flexibility and wearability has been investigated extensively [8]. For a satisfactory strain sensor, comprehensive sensing performances of nice flexibility, good response stability, wide response range and high sensitivity are urgently desired. However, there are still many challenges to develop a favorable strain sensor, for instance, the balance between high sensitivity and broad sensing range, complicated preparation technology, expensive raw materials, and so on.
To realize these sensing performances simultaneously, conductive polymer composites (CPCs) as the candidate materials of strain sensors have aroused wide attention because of good flexibility, cost-efficiency and excellent workability [[9], [10], [11], [12], [13]]. Up to now, in order to develop flexible strain sensors with CPCs, a lot of research has been carried out through employing conductive carbonaceous materials (carbon nanotubes (CNTs), carbon black (CB) and graphene) or metallic materials (Ag and gold nanowires/nanoparticles) as conductive fillers, and polymers with nice flexibility (silicon rubber, thermoplastic polyurethane (TPU), Ecoflex and polydimethylsiloxane (PDMS)) as matrix materials [[14], [15], [16], [17], [18], [19], [20]]. For example, Li et al. achieved a strain sensor with high sensitivity by transferring assembled graphene films onto PDMS matrix [21], which obtained a high gauge factor (GF) of 1037 in a range of 0–2% strain. Kang et al. sputtered Pt on the flexible polyurethane acrylate matrix and then constructed crack structures [22], obtaining a strain sensor with micro-crack structure and high sensitivity (GF of 2000 in strain range of 0–2%). Moreover, Wang et al. prepared an ultra-sensitive strain sensor based on the composite of gold/titanium thin film and PDMS, achieving an ultra-high GF of 5000 at 1% strain [23]. These strain sensors possessed high sensitivity (GF > 1000) and favorable stability except narrow sensing range (always about 1%–2%) and complex preparation process. In order to acquire a wider sensing range, TPU was chosen as the matrix material on the basis of the nice flexibility in our previous work. Ren et al. fabricated an ultra-stretchable strain sensor through decorating CNTs on electrospun TPU fibrous mat (CNTs/TPU) by a simple ultrasonic process [24]. The strain sensor based on CNTs/TPU composite mat showed extremely broad sensing range (900% strain), while its GF needs to be improved (only 19.96). Wang et al. developed a CNT/TPU based strain sensor with high performance by using a simple, low-cost and large scale wet spinning technology [15], and achieved a broad sensing range (320% strain) and a high GF of 97.1 at strain of 160–320% simultaneously. While the detection limit (5% strain) and response time (200 ms), which play an important role in sensing performance, still need to be promoted. Therefore, synchronously achieving low detection limit (<1% strain), high sensitivity (GF > 500), large stretchability (>200% strain), fast response time (<100 ms) and excellent stability (>5000 cycles) to meet the requirements of human motion detection remains a challenge for CPCs based strain sensors.
In this work, to address the issues as mentioned above, we present a wearable CB/TPU/Ecoflex strain sensor (CTESS). Zero-dimensional CB is applied as the conductive material due to its low-cost and good electrical conductivity, TPU is selected as the matrix material owing to the nice flexibility and cost efficiency. The CTESS is fabricated by decorating CB particles on aligned electrospun TPU fibrous mat through ultrasonication and encapsulation using Ecoflex to develop a sandwich structure. CB nanoparticles are decorated on TPU mat through the ultrasonication treatment. The electrospun TPU mesh coated with CB particles forms an intact 3D conductive network, guaranteeing the CTESS to suffer large deformations. The point-to-point contact mode of zero-dimensional CB nanoparticles is easy to respond to the deformation of the net structure during stretching, which endows the CTESS with good sensing ability. Sensing behaviors of CTESS, including strain range, sensitivity, response time, response stability and anti-interference performance towards temperature and humidity are investigated systematically. To evaluate the potential in practical applications, CTESS is assembled as artificial electronic skins to detect various human movements. The present study provides an effective strategy to achieve next-generation wearable electronic devices.
Section snippets
Materials
TPU (Elastollan 1185A) was purchased from BASF Co., Ltd. Tetrahydrofuran (THF) and N, N-dimethylformamide (DMF) were both supplied by Fuyu Fine Chemical Co., Ltd, Tianjin, China. CB (Vulcan XC72) was supplied by Cabot Corp., USA. Sodium dodecyl sulfonate (SDS) was supplied by Kangpuhuiwei Technology Co., Ltd, Beijing, China. All the chemicals are analytical grade and used directly without any treatment.
The preparation of CTESS
The preparation process of CTESS mainly includes electrospinning, ultrasonication and
Results and discussion
Fig. 1a illustrates the preparation process of CTESS, which mainly includes electrospinning, ultrasonication and encapsulation. Firstly, the pure TPU fibrous mat is fabricated by electrospinning. As shown in Fig. S2, the surface of the pure electrospun TPU fiber is smooth, and the electrospun TPU fibrous mat displays an interesting aligned wave-like structure. The thickness (only 54 μm) of TFM is displayed in Fig. S3a. Meanwhile, as shown in Fig. S3b, the joint points between adjacent fibers
Conclusions
In summary, we have successfully developed a smart and wearable CTESS with a sandwich structure by electrospinning, ultrasonication and encapsulation. The CTESS exhibits broad sensing range (225% strain) and ultrahigh GF of 3186.4 at the strain of 210–225%. The CTESS displays ultralow detecting limit (0.5% strain) and short response time (70 ms). The electrical response for CTESS is very steady even after 5000 stretching/releasing cycles under 40% strain, exhibiting good repeatability and
CRediT authorship contribution statement
Yi Zhao: Investigation, Writing - original draft. Miaoning Ren: Investigation, Data curation. Ying Shang: Investigation, Methodology. Jiannan Li: Investigation, Data curation. Shuo Wang: Investigation, Software. Wei Zhai: Writing - review & editing. Guoqiang Zheng: Formal analysis, Methodology. Kun Dai: Conceptualization, Supervision. Chuntai Liu: Resources, Supervision. Changyu Shen: Supervision, Validation.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors acknowledge the financial support of this research by National Natural Science Foundation of China (51773183, U1804133), National Natural Science Foundation of China-Henan Province Joint Funds (U1604253), Henan Province University Innovation Talents Support Program (20HASTIT001), Innovation Team of Colleges and Universities in Henan Province (20IRTSTHN002).
References (44)
- et al.
Ultra-stretchable triboelectric nanogenerator as high-sensitive and self-powered electronic skins for energy harvesting and tactile sensing
Nano Energy
(2020) - et al.
Highly stretchable and durable fiber-shaped strain sensor with porous core-sheath structure for human motion monitoring
Compos. Sci. Technol.
(2020) - et al.
Flexible electrically resistive-type strain sensors based on reduced graphene oxide-decorated electrospun polymer fibrous mats for human motion monitoring
Carbon
(2018) - et al.
Multifunctional flexible carbon black/polydimethylsiloxane piezoresistive sensor with ultrahigh linear range, excellent durability and oil/water separation capability
Chem. Eng. J.
(2019) - et al.
A highly stretchable carbon nanotubes/thermoplastic polyurethane fiber-shaped strain sensor with porous structure for human motion monitoring
Compos. Sci. Technol.
(2018) - et al.
Detection of non-joint areas tiny strain and anti-interference voice recognition by micro-cracked metal thin film
Nano Energy
(2017) - et al.
Highly stretchable and durable strain sensor based on carbon nanotubes decorated thermoplastic polyurethane fibrous network with aligned wave-like structure
Chem. Eng. J.
(2019) - et al.
Ultra-stretchable, durable and conductive hydrogel with hybrid double network as high performance strain sensor and stretchable triboelectric nanogenerator
Nano Energy
(2020) - et al.
Multifunctional stretchable strain sensor based on polydopamine/reduced graphene oxide/electrospun thermoplastic polyurethane fibrous mats for human motion detection and environment monitoring
Compos. B Eng.
(2020) - et al.
A highly stretchable, super-hydrophobic strain sensor based on polydopamine and graphene reinforced nanofiber composite for human motion monitoring
Compos. B Eng.
(2020)
Dual conductive network enabled superhydrophobic and high performance strain sensors with outstanding electro-thermal performance and extremely high gauge factors
Chem. Eng. J.
Pursuing prosthetic electronic skin
Nat. Mater.
Fingertip‐skin‐inspired highly sensitive and multifunctional sensor with hierarchically structured conductive graphite/polydimethylsiloxane foams
Adv. Funct. Mater.
A highly flexible and sensitive piezoresistive sensor based on MXene with greatly changed interlayer distances
Nat. Commun.
A wearable transient pressure sensor made with MXene nanosheets for sensitive broad-range human-machine interfacing
Nano Lett.
Triboelectric touch‐free screen sensor for noncontact gesture recognizing
Adv. Funct. Mater.
An intelligent artificial throat with sound-sensing ability based on laser induced graphene
Nat. Commun.
Bioinspired ultrasensitive and stretchable MXene-based strain sensor via nacre-mimetic microscale "brick-and-mortar" architecture
ACS Nano
Flexible and wearable carbon black/thermoplastic polyurethane foam with a pinnate-veined aligned porous structure for multifunctional piezoresistive sensors
Chem. Eng. J.
Significant stretchability enhancement of a crack-based strain sensor combined with high sensitivity and superior durability for motion monitoring
ACS Appl. Mater. Interfaces
Porous fibers composed of polymer nanoball decorated graphene for wearable and highly sensitive strain sensors
Adv. Funct. Mater.
A stretchable and highly sensitive graphene-based fiber for sensing tensile strain, bending, and torsion
Adv. Mater.
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