High strength and flexible aramid nanofiber conductive hydrogels for wearable strain sensors

In this study, tough and conductive hydrogels were printed by 3D printing method. The combination of thermo-responsive agar and ionic-responsive alginate can highly improve the shape fidelity. With addition of agar, ink viscosity was enhanced, further improving its rheological characteristics for a precise printing. After printing, the printed construct was cured via free radical polymerization, and alginate was crosslinked by calcium ions. Most importantly, with calcium crosslinking of alginate, mechanical properties of 3D printed hydrogels are greatly improved. Furthermore, these 3D printed hydrogels can serve as ionic conductors, because hydrogels contain large amounts of water that dissolve excess calcium ions. A wearable resistive strain sensor that can quickly and precisely detect human motions like finger bending was fabricated by a 3D printed hydrogel film. These results demonstrate that the conductive, transparent, and stretchable hydrogels are promising candidates as soft wearable electronics for healthcare, robotics and entertainment.

Download Full-text

Double-network hydrogel with adjustable surface morphology and multifunctional integration for flexible strain sensors

Soft Matter ◽

10.1039/d1sm00158b ◽

2021 ◽

Author(s):

Yang Yu ◽

Fengjin Xie ◽

Xinpei Gao ◽

Liqiang Zheng

Keyword(s):

Surface Morphology ◽

Flexible Electronics ◽

High Performance ◽

Strain Sensors ◽

Next Generation ◽

Double Network ◽

Conductive Hydrogels

The next generation of high-performance flexible electronics has put forward new demands to the development of ionic conductive hydrogels. In recent years, many efforts have been made toward developing double-network...

Download Full-text

Anisotropic, Wrinkled, and Crack-Bridging Structure for Ultrasensitive, Highly Selective Multidirectional Strain Sensors

Nano-Micro Letters ◽

10.1007/s40820-021-00615-5 ◽

2021 ◽

Vol 13 (1) ◽

Author(s):

Heng Zhang ◽

Dan Liu ◽

Jeng-Hun Lee ◽

Haomin Chen ◽

Eunyoung Kim ◽

...

Keyword(s):

Rational Design ◽

Full Range ◽

Human Motion ◽

Strain Sensors ◽

Gauge Factor ◽

Wearable Electronics ◽

Trade Off ◽

Human Motion Detection ◽

Sensing Applications ◽

Anisotropic Structures

AbstractFlexible multidirectional strain sensors are crucial to accurately determining the complex strain states involved in emerging sensing applications. Although considerable efforts have been made to construct anisotropic structures for improved selective sensing capabilities, existing anisotropic sensors suffer from a trade-off between high sensitivity and high stretchability with acceptable linearity. Here, an ultrasensitive, highly selective multidirectional sensor is developed by rational design of functionally different anisotropic layers. The bilayer sensor consists of an aligned carbon nanotube (CNT) array assembled on top of a periodically wrinkled and cracked CNT–graphene oxide film. The transversely aligned CNT layer bridge the underlying longitudinal microcracks to effectively discourage their propagation even when highly stretched, leading to superior sensitivity with a gauge factor of 287.6 across a broad linear working range of up to 100% strain. The wrinkles generated through a pre-straining/releasing routine in the direction transverse to CNT alignment is responsible for exceptional selectivity of 6.3, to the benefit of accurate detection of loading directions by the multidirectional sensor. This work proposes a unique approach to leveraging the inherent merits of two cross-influential anisotropic structures to resolve the trade-off among sensitivity, selectivity, and stretchability, demonstrating promising applications in full-range, multi-axis human motion detection for wearable electronics and smart robotics.

Download Full-text

High strength and conductive hydrogel with fully interpenetrated structure from alginate and acrylamide

e-Polymers ◽

10.1515/epoly-2021-0043 ◽

2021 ◽

Vol 21 (1) ◽

pp. 391-397

Author(s):

Tao Liu ◽

Ripeng Zhang ◽

Jianzhi Liu ◽

Ling Zhao ◽

Yueqin Yu

Keyword(s):

Mechanical Performance ◽

Three Dimensional ◽

High Strength ◽

Extreme Environment ◽

Natural Polymers ◽

Conductive Hydrogel ◽

Wide Range ◽

Interpenetrated Structure ◽

Conductive Hydrogels ◽

Conductive Properties

Abstract Highly stretched and conductive hydrogels, especially synthetized from natural polymers, are beneficial for highly stretched electronic equipment which is applied in extreme environment. We designed and prepared robust and tough alginate hydrogels (GMA-SA-PAM) using the ingenious strategy of fully interpenetrating cross-linking, in which the glycidyl methacrylate (GMA) was used to modify sodium alginate (SA) and then copolymerized with acrylamide (AM) and methylenebisacrylamide (BIS) as cross-linkers. The complete cross-linked structures can averagely dissipate energy and the polymer structures can maintain hydrogels that are three-dimensional to greatly improve the mechanical performance of hydrogels. The GMA-SA-PAM hydrogels display ultra-stretchable (strain up to ∼407% of tensile strain) and highly compressible (∼57% of compression strain) properties. In addition, soaking the GMA-SA-PAM hydrogel in 5 wt% NaCl solution also endows the conductivity of the hydrogel (this hydrogel was named as GSP-Na) with excellent conductive properties (5.26 S m−1). The GSP-Na hydrogel with high stability, durability, as well as wide range extent sensor is also demonstrated by researching the electrochemical signals and showing the potential for applications in wearable and quickly responded electronics.

Download Full-text

Stretchable Zwitterionic Conductive Hydrogels with Semi‐Interpenetrating Network Based on Polyaniline for Flexible Strain Sensors

Macromolecular Chemistry and Physics ◽

10.1002/macp.202100165 ◽

2021 ◽

pp. 2100165

Author(s):

Xiaoling Chen ◽

Weizhen Hao ◽

Tiao Lu ◽

Tian Wang ◽

Caixin Shi ◽

...

Keyword(s):

Strain Sensors ◽

Interpenetrating Network ◽

Conductive Hydrogels

Download Full-text

Graphene Oxide-Based Composite Organohydrogels with High Strength and Low Temperature Resistance for Strain Sensors

Soft Matter ◽

10.1039/d1sm01655e ◽

2022 ◽

Author(s):

Rui Zhao ◽

Li Jiang ◽

Ping Zhang ◽

Dan Li ◽

Zhenzhong Guo ◽

...

Keyword(s):

Mechanical Properties ◽

Graphene Oxide ◽

Low Temperature ◽

Rapid Development ◽

High Strength ◽

Strain Sensors ◽

Temperature Resistance ◽

Polymeric Hydrogel ◽

Low Temperature Resistance

In the recent years, a rapid development of the polymeric hydrogel-based sensors has been witnessed. However, conventional hydrogels often exhibit poor mechanical properties. Additionally, the use of these sensors at...

Download Full-text

Highly stretchable, self-adhesive, biocompatible, conductive hydrogels as fully polymeric strain sensors

Journal of Materials Chemistry A ◽

10.1039/d0ta07390c ◽

2020 ◽

Vol 8 (39) ◽

pp. 20474-20485

Author(s):

Dong Zhang ◽

Yijing Tang ◽

Yanxian Zhang ◽

Fengyu Yang ◽

Yonglan Liu ◽

...

Keyword(s):

Strain Sensors ◽

Surface Adhesion ◽

Human Movements ◽

Conductive Hydrogel ◽

Highly Stretchable ◽

Strong Surface ◽

Conductive Hydrogels

A new fully polymeric conductive hydrogel sensor with IPN structure was developed, which achieved ultra-high stretchability, strong surface adhesion, and high sensing stability in response to both large and subtle human movements.

Download Full-text

Polymer-Based Self-Standing Flexible Strain Sensor

Journal of Sensors ◽

10.1155/2010/659571 ◽

2010 ◽

Vol 2010 ◽

pp. 1-5 ◽

Cited By ~ 7

Author(s):

Fernando Martinez ◽

Gregorio Obieta ◽

Ion Uribe ◽

Tomasz Sikora ◽

Estibalitz Ochoteco

Keyword(s):

Electrical Conductivity ◽

Electrical Resistance ◽

Strain Sensor ◽

Strain Sensors ◽

Gauge Factor ◽

Wearable Electronics ◽

Rehabilitation Devices ◽

Flexible Strain Sensor

The design and characterization of polymer-based self-standing flexible strain sensors are presented in this work. Properties as lightness and flexibility make them suitable for the measurement of strain in applications related with wearable electronics such as robotics or rehabilitation devices. Several sensors have been fabricated to analyze the influence of size and electrical conductivity on their behavior. Elongation and applied charge were precisely controlled in order to measure different parameters as electrical resistance, gauge factor (GF), hysteresis, and repeatability. The results clearly show the influence of size and electrical conductivity on the gauge factor, but it is also important to point out the necessity of controlling the hysteresis and repeatability of the response for precision-demanding applications.

Download Full-text