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Stretchable Ti3C2Tx MXene/Carbon Nanotube Composite Based Strain Sensor with Ultrahigh Sensitivity and Tunable Sensing Range Yichen Cai,† Jie Shen,§ Gang Ge,† Yizhou Zhang,† Wanqin Jin,§ Wei Huang,† Jinjun Shao,*,† Jian Yang,*,‡ and Xiaochen Dong*,†,∥ †
Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211800, China ‡ College of Materials Science and Engineering, Nanjing Tech University (NanjingTech), Nanjing 211800, China § State Key Laboratory of Materials-Oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), Nanjing 211800, China ∥ School of Physical and Mathematical Sciences, Nanjing Tech University (NanjingTech), Nanjing 211800, China S Supporting Information *
ABSTRACT: It remains challenging to fabricate strainsensing materials and exquisite geometric constructions for integrating extraordinary sensitivity, low strain detectability, high stretchability, tunable sensing range, and thin device dimensions into a single type of strain sensor. A percolation network based on Ti3C2Tx MXene/carbon nanotube (CNT) composites was rationally designed and fabricated into versatile strain sensors. This weaving architecture with excellent electric properties combined the sensitive twodimensional (2D) Ti 3 C 2 Tx MXene nanostacks with conductive and stretchable one-dimensional (1D) CNT crossing. The resulting strain sensor can be used to detect both tiny and large deformations with an ultralow detection limit of 0.1% strain, high stretchability (up to 130%), high sensitivity (gauge factor up to 772.6), tunable sensing range (30% to 130% strain), thin device dimensions (5000 cycles). The versatile and scalable Ti3C2Tx MXene/CNT strain sensors provide a promising route to future wearable artificial intelligence with comprehensive tracking ability of real-time and in situ physiological signals for health and sporting applications. KEYWORDS: MXene, carbon nanotubes, ultrasensitivity, artificial electronic skin, controllable sensing range
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demonstrated by a combination of innovation in nanomaterials, device fabrication technology, and mechanism optimization. Despite impressive advances recently, the integration capability of a single-type versatile sensor for low strain detectability as small as artery pulses, high stretchability as large as entire body motions, ultrahigh sensitivity, tunable sensing ranges, and thin device dimensions still remains a challenge. Therefore, a combination of rational sensing materials and the design of the geometric structures are expected to be effective approaches to achieve these goals. MXenes, a new class of two-dimensional (2D) transition metal carbides and carbonitrides with metallic conductivity, excellent mechanical properties, and hydrophilic surface, show
tretchable and wearable strain-sensing microelectronics have attracted a huge surge of interest with diverse applications, ranging from epidermal sensors to healthmonitoring systems.1−11 To date, much ongoing effort has been made to develop large-area and high-performance stretchable sensing devices to capture and monitor various physical stimuli and physiological signals. Unfortunately, conventional strain gauge sensors based on constituent metal and semiconductor materials can detect only a narrow range of strain (ε < 5%) and exhibit low gauge factors (GF ≈ 2) due to their rigid nature.12,13 To address these issues, a variety of alternative nanomaterials have been used to design skin-like sensitive strain sensors, such as graphene,10,14−20 carbon black,21−24 carbon nanotubes,25−27 metal nanoparticles,28 and nanowires.29,30 On the other hand, rational nanotechnologies, such as micro- or nanostructures, offered opportunities in fabricating innovative strain sensors.31−33 The high stretchability of >800%,15 GF > 3000, and low sensing range down to 0.008%34 have been © 2017 American Chemical Society
Received: September 2, 2017 Accepted: December 4, 2017 Published: December 4, 2017 56
DOI: 10.1021/acsnano.7b06251 ACS Nano 2018, 12, 56−62
Article
Cite This: ACS Nano 2018, 12, 56−62
Article
ACS Nano
Figure 1. (a) Fabrication process of a sandwich-like Ti3C2Tx MXene/CNT layer. (b) Tyndall effect of MXene (Ti3C2Tx) and CNT suspension. (c, d) TEM images of Ti3C2Tx flakes and SWCNTs, respectively. (e) Photographs of a strain sensor belt clipped on two clamps before and after stretching up to 100% and 200%, respectively.
great promise in the electrochemical energy field, such as supercapacitors,35 Li(Na)-ion batteries,36−38 and electrocatalysis.39 These 2D materials also exhibit great potential in developing next-generation high-performance sensing devices.40 However, a colloidal Ti3C2Tx MXene solution upon delamination contains around 1-nm-thick 2D flakes with lateral sizes up to several micrometers with high aspect ratios. It is difficult to assemble individual Ti3C2Tx MXene sheets into ordered macroscopic geometric structures and excellent connection types without sacrificing their excellent mechanical and electrical properties.41,42 Thus, a well-designed structure is of paramount importance, and a simple, scalable, and effective hierarchical structure is also required to fully utilize the advantages of these materials, for the purpose of practical sensing devices.38 In this work, Ti3C2Tx MXenes43 combined with CNTs are presented to the best of our knowledge in manufacturing versatile and scalable strain sensors. Sandwich-like Ti3C2Tx MXene/CNT sensing layers (1−2 μm) were fabricated by using delaminated Ti3C2Tx MXene flakes and hydrophilic single-walled carbon nanotubes (SWNTs) through a layer-bylayer (LBL) spray coating technique. The water-based assembled sandwich-like microstructure provides the ultrathin devices with a low limit of detection as small as 0.1%, high sensitivity (a gauge factor up to 772.60), tunable sensing range (30% to 130% strain), and thin device dimension (
