Thermally stable, adhesively strong graphene/polyimide films for inkjet printing ultrasound sensors

Targeting for flexible, broadband ultrasound sensors, a new breed of nanographene platelet (NGP)/polyimide (PI) film is inkjet printed with morphologically optimized NGP/poly (amic acid) hybrid-based nanocomposite ink. The ink is produced with high-shear liquid phase exfoliation from inexpensive bulk graphite, manifesting good printability and high graphene concentration as high as 13.1 mg mL(-1). Featuring an ultra-thin thickness (similar to 1 mm only), the inkjet-printed NGP/PI film sensor is demonstrated to possess excellent thermal stability and high adhesive strength reaching the American Society for Testing and Materials 5B level. The highly uniform and consolidated NGP/PI nanostructure in the sensor enables the formation of pi-pi interaction between NGPs and PI polymer matrix, and the quantum tunneling effect is triggered among NGPs when ultrasound traverses the sensor. This sensing mechanism endows the NGP/PI sensor with good sensitivity, fidelity and accuracy, showing comparable performance as prevailing commercial ultrasound sensors such as piezoelectric sensors. The film sensor has a proven gauge factor as high as 739, when sensing ultrasound at 175 kHz, and an ultrabroad responsive spectrum up to 1.6 MHz. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

A new NGP/PI film sensor with excellent thermal stability and high adhesive strength has been developed, demonstrating good sensitivity and accuracy in ultrasound sensing.