Ultra-sensitive, Multi-directional Flexible Strain Sensors Based on an MXene Film with Periodic Wrinkles

Abstract

The fast-growing motion capturing/monitoring technique has raised a great demand for flexible strain sensors. For capturing complex motions (e.g., facial motion), both the strain amplitude and direction should be accurately detected. Although some reported sensors based on anisotropic conductive networks are proved to show accurate localization of strain directions, it is still a great challenge to achieve both high sensitivity and a high sensing range in these designs. Here, a self-assembled Ti 3 C 2 T x MXene film with parallel and periodic wrinkles is fabricated on a stretchable poly(dimethylsiloxane) substrate for constructing multidirectional strain sensors. During stretching, relative slip and crack will occur between the stacked MXene nanosheets, which contribute to high structural sensitivity in the MXene film. Meanwhile, the wrinkled structure contributes to high stretchability. As a result, the sensor based on the film with one-dimensional periodic wrinkles shows a large sensing range (>50%) and a gauge factor of 45. Furthermore, the sensor can accurately detect both the strain amplitude and direction by using the MXene film with two-dimensional wrinkles. It shows distinguishable electrical responses when detecting different-amplitude human/robot motions such as joint bending and walking. Additionally, the directions in complex human motions (e.g., facial motion) can also be well-tracked. This work provides an effective strategy to detect multi-directional motions.

Retraction of “Three-Axial Strain-Triggered Multimode Wrinkles with Tuneable Frictional and Optical Performances”

“…It is well known that striped wrinkles are generated on the film surface under uniaxial compression, 15,16 while labyrinth-like wrinkles form under isotropic compression. 8,17 Releasing equibiaxial prestrain in sequence leads to the formation of herringbone wrinkles 18,19 or crossing patterns, 20,21 while nonequibiaxial compression can generate herringbone wrinkles with different jog angles. 19,22 Asymmetrically biaxial loading (with varied intersection angles) can obtain unique chiral microwrinkle structures.…”

“…The morphologies and orientations are controlled by stress anisotropy and loading history. It is well known that striped wrinkles are generated on the film surface under uniaxial compression, , while labyrinth-like wrinkles form under isotropic compression. , Releasing equibiaxial prestrain in sequence leads to the formation of herringbone wrinkles , or crossing patterns, , while nonequibiaxial compression can generate herringbone wrinkles with different jog angles. , Asymmetrically biaxial loading (with varied intersection angles) can obtain unique chiral microwrinkle structures . The interference of two wrinkling generations with a variable angle can induce various two-dimensional surface structures such as checkerboard-like and rippled patterns. , Hierarchical wrinkles with superimposed different scales have also been fabricated through alternate film deposition and stress loading (heat shrinkage or mechanical deformation). − …”

Recent advances in smart wearable sensors as electronic skin

“…Discernible responses were also observed in different human motions (e.g., joint bending, walking, and facial expressions). 90 Conductivity and high sensitivity of capacitive pressure sensing are also achieved using conductive polymers to create electrodes and sandwich layers. 54 The breathability (ability of the e-skin to allow air to pass through) is also a crucial specification that can be beneficial.…”

Sandwich-Type Self-Healing Sensor with Multilevel for Motion Detection

“…However, it is important to note that traditional conductive fillers are often loosely distributed within the matrix, resulting in a lack of synergistic interactions. This not only compromises the original properties of the matrix but also leads to unstable sensing performance in the composite material. , To address this issue, it is advisable to enhance the traditional conductive fillers, such as carbon nanotubes (CNTs), by modifying them with superior interaction forces. For example, Ding et al incorporated silver-precipitated CNT nanoparticles into a self-healing elastomer, which led to improved mechanical properties of the material.…”