A highly sensitive flexible bimodal sensor with uniform pores based on natural polymers for human-computer...

Flexible sensors with uniform pores have garnered significant attention due to their superior sensor performance. However, the fabrication of flexible sensors with uniform pores that simultaneously exhibit excellent mechanical properties and sensing performance remains a challenge. In this paper, we propose a method for fabricating flexible sensors with uniform pores by employing a bidirectional freeze-drying technique that integrates a dual interpenetrating network formed by the natural biopolymer sodium alginate and silk fibroin, along with a magnetic conductive filler that responds to both force and magnetism. The formation of an interpenetrating network between sodium alginate, silk fibroin, and metal ions enhances the structural stability of the complex but also increases the β-sheets in silk fibroin and improves the cross-link density. The bidirectional freezing technique was utilized to control ice crystals' vertical and horizontal growth, resulting in a uniformly distributed pore structure and yielding a sensor with excellent deformability and mechanical properties. By incorporating modified conductive fillers, the sensors demonstrate remarkable sensitivity (magnetic 0.47 mT^-1, tensile 6.01, bending -0.76, pressure -1.14 kPa^-1) along with long-lasting signal stability and reusability. Moreover, the sensor can produce the same or opposite signals under different stimuli, showcasing signal discriminability. Additionally, the sensor can function as a wearable electronic device for monitoring human motion signals and can be utilized by individuals who have lost their voices to transmit information via Morse code. The sensor can be integrated into a multifunctional glove for robotic hand control, presenting significant potential for applications in human-computer interaction.