Preparation and characterization of functional dual network hydrogel for motion monitoring in smart bra

Abstract

The smart bra is a kind of sports underwear with providing health monitoring and comfort protection for women breast in sports. Developing smart sensing materials that combine comfort and functionality for sensing breast condition remains a challenge. Here, natural polysaccharide sodium alginate (SA), acrylamide (AM) monomer and chitosan (CS) and polypyrrole (PPy) in-situ polymerized from pyrole (Py) monomer were used as raw materials to successfully synthesize double network conductive hydrogel by two-step method. The results show that in the hydrogels, the entanglement and interpenetration of macromolecules produce toughness (tensile/compressive strength is ∼0.248 MPa/∼2.836 MPa), elasticity (tensile/compression elastic recovery rate is∼94.06 %/∼98.41 %) and durability (after 30 tensile/compression cycles conducting at 25 %, 50 % and 100 % constant strain keep at high recovery rate). The rich moisture content provides its adhesion (adhesion strength ∼4.7557 kPa) and flexibility (bending stiffness 1.0843 cN cm∼), presenting sufficient adhesion reliability and robustness to different substrates. The addition of PPy enables the hydrogel to have conductivity (6.77 × 10−2 S cm−1) and sensing performance (tensile/compression sensitivity is ∼1.94/∼1.43). The conductive hydrogel, as a flexible strain sensor, shows good adhesion, flexibility, elasticity and sensitivity in application of sports smart bra, can detect both the tensile behavior of skin and the compression state of tissue through its mechano-electricity, and accurately sense the changes of physiological parameters during movement. The conductive hydrogel with high elasticity and strength has broad application prospects in smart bra.