Integration of porous graphene and 3D-printed piezopolymer for flexible ultrasound transducers

• Laser-induced graphene is combined with piezopolymer to develop ultrasound patches. • Piezopolymer infiltration into porous graphene increases its contact area interaction with graphene. • Increased contact area of the piezopolymer with graphene enhances its piezoelectric response. • Enhanced piezoelectric response improves the ultrasound patch acoustic performance. • Central frequency is tunable by adjusting the piezopolymer thickness. Ultrasound technology is crucial in diagnostic imaging, making it widely used in medical applications. However, traditional ultrasound transducers face limitations in flexibility and ease of fabrication, leading to the exploration of thin-film and flexible piezoelectric materials. Here, we present a novel approach that combines laser graphitization with 3D printing to integrate flexible laser-induced porous graphene (LIG) with poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE), resulting in the development of flexible LIG/PVDF-TrFE ultrasound patches. The thickness of PVDF-TrFE is adjusted to tune the central frequency of the ultrasound transducer, allowing customization within a range of 10 to 28 MHz. LIG-based ultrasound transducer demonstrates a high signal amplitude of 6.72 V and a signal-to-noise ratio (SNR) of 433, along with a −6 dB bandwidth of 8.86 MHz (37 %). The LIG-based transducer exhibits higher acoustic performance compared to the smooth silver-based transducer. A high-quality two-dimensional ultrasound image, including a B-mode image of a cyst phantom, demonstrates the transducer’s imaging capabilities. The patterning of LIG-based electrodes facilitates the desired sensor configuration, demonstrating the suitability of our novel technique for producing flexible transducer arrays without dicing and cutting. The materials cost of our LIG/PVDF-TrFE transducer is under $5 per unit, making it a low-cost solution for ultrasound patches.