Electrospinner: Highly conductive and sensitive alginate hydrogel strain sensors fabricated using near-field electrohydrodynamic direct-writing process

Research background

Hydrogel flexible sensors have attracted extensive attention due to their wearability, biocompatibility, and precise signal transmission capabilities. However, hydrogel strain sensors prepared by traditional printing or manual injection methods are difficult to balance between mechanical strength and sensing properties, limiting their applications.

Research methods

Polyvinyl alcohol and polyacrylamide are loosely cross-linked with sodium alginate by chemical cross-linking. Subsequently, MXene nanosheets are introduced to construct a cross-linked hydrogel conductive network, and hydrogel strain sensors are prepared by EHD printing.

Research highlights

High conductivity:

The ions in the EHD-printed hydrogel move directionally under an external enhanced electric field to form a more uniform and dense porous conductive network, with a conductivity of 0.49 S/m, which is 0.29 S/m higher than that of the hydrogel film prepared by manual injection.

High sensitivity:

The addition of MXene materials improves the compactness of the sensor conductive network, and the EHD printing process basically eliminates the void defects in the hydrogel, making the porous network structure more uniform, dense and stable, with a sensitivity measurement coefficient of 1.54 (0-100% strain).

Good stability:

Long-term stability tests at 50% strain showed that the sensor was stable for up to 2000 seconds (500 cycles), showing good stability.

Excellent mechanical properties:

The cross-linking between MXene nanosheets and the hydrogel network forms more hydrogen bonds, and the high voltage electric field applied during the printing process helps to improve the distribution uniformity and orientation uniformity of the printed material, thereby improving the mechanical properties of the hydrogel. The tensile strength and elongation at break of the M3-S3PB hydrogel are 0.17 MPa and 787%, respectively.

Excellent adhesion:

The sensor prepared by EHD printing has strong physical affinity and can be effectively attached to the surface of different objects with the assistance of electrostatic force, meeting the requirements of strain sensors and achieving high-quality signal acquisition.

The connection between EHD printing technology and electrospinning

Material preparation and compounding:

It can be used to prepare nanofibers, which can be used as substrates or reinforcement materials for sensors. Through electrospinning, nanofiber structures with high specific surface area and good mechanical properties can be manufactured.

Nanofibers prepared by electrospinning can be combined with hydrogels (such as alginate hydrogels) to form composite materials. Such composite materials can improve the conductivity and sensitivity of sensors.

Enhanced sensor performance

Sensitivity improvement:

Electrospinning technology can optimize the sensitivity of sensors by adjusting the diameter and arrangement of fibers. When combined with EHD printing, a uniform conductive network can be formed in the hydrogel, further improving the performance of the sensor.

Mechanical properties:

Nanofibers prepared by electrospinning can enhance the mechanical strength of hydrogels and keep the sensor stable under repeated strain.

Conductive fillers:

During the electrospinning process, conductive materials (such as MXene or carbon nanotubes) can be incorporated into polymer solutions to prepare conductive nanofibers. These conductive nanofibers can be combined with EHD-printed hydrogels to form highly conductive composite materials.

Uniform conductive network:

EHD printing can ensure the uniform distribution of conductive materials in the hydrogel, further improving the conductivity of the sensor.

Conclusion

Flexible hydrogel strain sensors prepared by EHD printing technology have high stability, high conductivity and high sensitivity. The interaction between SA and MXene nanosheets and polymer networks significantly improved the electrical and mechanical properties of the hydrogel. The orientation of the internal material components of the hydrogel by the external high voltage electric field led to the formation of a dense porous network structure, which made the M3-S3PB hydrogel strain sensor have excellent mechanical properties, high sensitivity, low detection limit and good sensing stability in the strain range of 1-500%.

Electrospinning Nanofibers Article Source:

https://www.sciencedirect.com/science/article/abs/pii/S0141813024076116?via%3Dihub