Session: 04-26-01: Advanced Material Innovations in Wearable Biomedical Devices and Structures

Paper Number: 142112

142112 - Integration of 3d Porous Graphene With Piezoelectric Material for Wearable Ultrasound Transducer 

Ultrasound technology has emerged as a versatile and indispensable tool with applications in various specialized fields, such as non-invasive diagnostic imaging, therapeutic approaches for targeted treatments, and non-destructive testing of material structures. Diagnostic ultrasound has the potential to provide precise muscle-level evaluation of musculoskeletal injuries by providing quantitative biofeedback during physical exercise for effective rehabilitation. Ultrasound imaging relies on transmitting ultrasound pulses into the medium and detecting reflected echoes from different tissue interfaces. Therefore, ultrasound imaging requires an ultrasound transducer (UST) that can efficiently convert electrical energy into mechanical (acoustic pressure) energy, and vice versa (i.e., piezoelectric material). Traditional USTs are primarily designed for hand-held use and made of piezoelectric ceramics, which are not suitable for imaging during dynamic activity. We present an innovative approach for developing disposable UST patches that relies on graphene electrodes and additive manufacturing of thin piezoelectric films to meet this need.

We employ a facile, rapid, and scalable laser photothermal approach to generate 3D porous graphene from thin films of polyimide. By utilizing a far-infrared laser, localized photothermal irradiation causes a temperature increase within the laser's focused area. This rise in temperature breaks the covalent bonds between carbon atoms in the polyimide precursor, resulting in the formation of porous structures as the gaseous molecules in the polyimide evaporate. Subsequently, a composite piezoelectric material is created by integrating Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) with 3D porous graphene. To complete the fabrication process, the transducer is subjected to poling process. This poling process facilitate the alignment of the piezoelectric domains within the PVDF-TrFE composite, enhancing its overall piezoelectric properties. The fabrication was completed by gold sputter-coating and deposition of a 1µm thick parylene film for passivation. Piezoelectric coefficient (D33) and signal-to-noise ratio (SNR) of the UST were characterized by applying compressional force and using pulse-echo measurements, respectively.

Deposition and infiltration of PVDF into graphene pores increased surface area interaction and produced thin and durable wearable UST patches with enhanced piezoelectric performance and high imaging resolution (D33=99 pm/V, SNR=109.45). To demonstrate the potential of our manufacturing approach and graphene-based USTs, we fabricated an M-shaped transducer. Hydrophone measurements were then conducted to visualize the M logo, illustrating the suitability of our novel technique for applications requiring special ultrasound geometries. Furthermore, the scalability and precise patterning capability of our photothermal laser manufacturing technology enable the creation of array transducers with a pitch of ∼350 µm. The production cost of graphene-based UST is estimated to be under $5 per unit, making them a low-cost solution for precise, real-time muscle evaluation in clinical and ambulatory settings.

Presenting Author: Shirin Movaghgharnezhad George Mason University

Presenting Author Biography: Dr. Shirin Movaghgharnezhad received her Ph.D. in Mechanical Engineering from George Mason University. She is currently a Research Assistant Professor at the Applied Biosensing Laboratory, George Mason University. She is passionate about advancing scientific knowledge in the realm of micro/nanomaterials, particularly in the development of innovative methods and strategies for fabricating laser-induced 3D graphene-based functional materials and composites with enhanced properties for various applications.

Authors:

Shirin Movaghgharnezhad George Mason University
Clayton Baker George Mason University
Ehsan Ansari George Mason University
Dulcce Valenzuela George Mason University
Ahmed Bashatah George Mason University
Pilgyu Kang George Mason University
Parag Chitnis George Mason University