Flexible in-plane microsupercapacitors with electrospun NiFe₂O₄ nanofibers for portable sensing applications

The development of wearable electronic devices in recent decades has brought new opportunities in the exploration of micro-supercapacitors as energy storage units. In this work, we report the fabrication of flexible NiFe₂O₄ nanofiber based in-plane micro-supercapacitors (MSCs), which can serve as energy storage receptors to drive a portable graphene pressure sensor. The obtained NiFe₂O₄ nanofiber electrodes exhibited a specific capacitance of 2.23 F cm^-3 at the scan rate of 100 mV s^-1, and excellent rate capability and robust cycling stability with a capacitance retention of 93.6% after 10000 charge/discharge cycles. Moreover, the in-plane MSCs have superior flexibility and outstanding stability even after repetition of charge/discharge cycles during the convex and concave bending states. The MSCs offered a high energy density of 0.197 mWh cm^-3 and power density up to 2.07 W cm^-3. We also coupled the MSCs with a graphene pressure sensor as a micro-integrated system to implement it's pressure response function and used MATLAB to simulate this system behavior as well. The performance of the designed systems exhibited a stable pressure response, and the simulated results coincide well with the experimental data, demonstrating its feasibility in wearable electronic devices.