A highly sensitive wearable flexible strain sensor based on polycrystalline MoS₂ thin film

Area of Science:

• Materials Science
• Nanotechnology
• Mechanical Engineering

Background:

• Piezoresistive materials are crucial for developing advanced strain sensors.
• Flexible electronics require robust and sensitive strain-sensing components.
• Molybdenum disulfide (MoS2) shows promise for piezoresistive applications.

Purpose of the Study:

• To investigate the piezoresistive properties of polycrystalline MoS2 films for strain sensing.
• To enhance the sensing stress range and durability of MoS2-based flexible strain sensors.
• To develop a cost-effective and scalable fabrication approach for MoS2 flexible sensors.

Main Methods:

• Fabrication of flexible MoS2/PET devices.
• Encapsulation of MoS2 strain sensors with SU-8 layers of varying thicknesses.
• Characterization of piezoresistive properties and gauge factor (GF) under different stress levels.
• Assessment of sensor durability through mechanical stress tests and body movement simulations.

Main Results:

• A flexible MoS2/PET device exhibited a gauge factor (GF) of 102 ± 5 within a ~7 MPa to ~14 MPa stress range.
• SU-8 encapsulation improved the sensing stress range, with GF values of 80 ± 2 (2 μm SU-8) and 12 ± 1 (10 μm SU-8) at higher stresses.
• Encapsulated devices maintained integrity beyond 14 MPa and demonstrated durability with body movements.

Conclusions:

• Polycrystalline MoS2 films are suitable for flexible strain-sensing applications.
• SU-8 encapsulation is an effective strategy to enhance the stress range and durability of MoS2-based sensors.
• The developed fabrication method offers a scalable and cost-effective route for producing advanced flexible strain sensors.