Industrial Electrospinning Machine| Highly stretchable, self-adhesive, conductive, and tough hydrogelreinforced with cellulose nanofibers for wearable biosensor andultrasonic nanogenerator

Research Team of Professor Li Dawei & Professor Zhang Wei from Nantong University: Nanofiber Hydrogel Strain Sensor and Ultrasonic Nanogenerator

In recent decades of rapid technological development, advanced technologies such as semiconductors and wearable devices have gradually integrated into all aspects of daily life. However, sensor technology still faces challenges including poor signal acquisition accuracy and inability to maintain long-term stable adhesion to human skin. Conductive hydrogels, characterized by high mechanical properties, excellent conductivity, and good biocompatibility, can also be assembled into nanogenerators to harvest various energy forms and power small electronic devices.

Recently, the research team of Professor Li Dawei and Professor Zhang Wei from Nantong University published their latest research findings titled "Highly Stretchable, Self-Adhesive, Conductive, and Tough Hydrogel Reinforced with Cellulose Nanofibers for Wearable Biosensor and Ultrasonic Nanogenerator" in the journal Chemical Engineering Journal. The researchers prepared MXene/CNF/PDA/PAM hydrogel with high mechanical properties, conductivity, and self-adhesion through thermal cross-linking gel technology. By combining with PA6 membrane and encapsulating with Eco-flex, they constructed a triboelectric nanogenerator with excellent electrical performance under ultrasonic stimulation.

The study demonstrated that incorporating cellulose nanofibers (CNF) enhanced the tensile strength of PDA/PAM hydrogel, while appropriate addition of MXene endowed the hydrogel with good conductivity. Furthermore, the inclusion of CNF and MXene provided the hydrogel with excellent compressive properties. The MXene/CNF/PDA/PAM hydrogel shows promising potential for smart wearable sensors.

Fig. 1: Material characterization of MXene/CNF/PDA/PAM hydrogel

The thermally cross-linked MXene/CNF/PDA/PAM hydrogel exhibited a 3D network structure in SEM images. FTIR and XPS experiments confirmed the successful incorporation of MXene into the hydrogel.

Fig. 2: Mechanical properties of MXene/CNF/PDA/PAM hydrogel

As shown in Figure 2, the MCPP hydrogel could support a 200g weight (Fig. 2a). Additionally, the MCPP hydrogel could be stretched to 8 times and twisted to 7 times its original length. After 80% compression, it easily recovered to its original state, demonstrating excellent flexibility and resilience. The hydrogel showed an elongation of 847.4% and a fracture strength of 94.8 kPa.

With the addition of MXene, the PAM hydrogel exhibited improved conductivity (Fig. 3b). The MXene/CNF/PDA/PAM hydrogel not only generated electrical responses under small strains (1%-10%), but also achieved a maximum sensing range of 300% with a sensitivity of 2.84. After 1000 stretching cycles, it maintained stable resistance change rates, demonstrating excellent fatigue resistance and stability (Fig. 3g).

Fig. 3: Electrical properties of MXene/CNF/PDA/PAM hydrogel

In physiological and motion signal monitoring applications, the MXene/CNF/PDA/PAM hydrogel accurately captured ECG signals, EMG signals, and human movement patterns (Fig. 4), exhibiting outstanding sensing performance and great potential in human physiological and motion monitoring applications.

Fig. 4: Applications of MXene/CNF/PDA/PAM hydrogel

Electrical performance tests of the MCPP nanogenerator revealed its high output performance (Fig. 5). Under ultrasonic stimulation, the MCPP nanogenerator showed excellent electrical output with voltage and current of 2V and 1.6µA respectively. To enhance the voltage signal, a PA6 membrane was added to the hydrogel's upper surface, increasing the output to approximately 4.1V and 4.8µA.

Fig. 5: Construction and electrical output performance of MCPP generator

Application tests including capacitor charging, LED lighting, and non-contact power generation demonstrated the device's great potential in small-scale power supply and implantable generators. Fast charging and powering multiple LEDs confirmed its superior electrical output performance. In non-contact power generation tests, when placed beneath a 1cm-thick beef slice and exposed to ultrasonic stimulation, the generator still produced 2.2V, further verifying its high power generation capability.

Fig. 6: Power supply applications of MCPP generator

Paper link: https://authors.elsevier.com/sd/article/S1385-8947(25)04845-4