Piezoelectric-based conformable electronics have emerged as a promising field, especially in healthcare monitoring and biomedical applications. These technologies have been extensively researched, aiming to enable on-body vital sign decoding, mechanical energy harvesting, and deep tissue imaging through ultrasound transducers.
Among various imaging methods, piezoelectric-based ultrasound transducers have gained significant attention due to their advantages over computed tomography (CT) and magnetic resonance imaging (MRI), which involve ionizing radiation and are less accessible.
In recent years, researchers have focused on developing piezoelectric-based conformable ultrasound electronics to address these challenges and expand their applications. These technologies have shown promise in monitoring cardiac functions, imaging blood flow, bladder volume observation, muscle activation, and transdermal drug delivery, among others.
Piezoelectric Materials in Ultrasound Transducers
Piezoelectric materials play a crucial role in the performance of ultrasound transducers. While previous studies mainly used commercial lead zirconate titanate (PZT) ceramics, recent investigations have explored single crystals with morphotropic phase boundary (MPB) compositions, such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT).
These single crystals offer significantly improved electromechanical coupling factors and piezoelectric coefficients compared to PZT ceramics, making them promising candidates for ultrasonic transducers and energy-harvesting devices.
However, PMN-PT solid solutions have limited temperature usage ranges due to their relatively low Curie temperature and rhombohedral-to-tetragonal phase transition temperature. To address this limitation, researchers have turned to crystals doped with rare-earth elements, such as Sm3+-doped PMN-PT and Nd3+-doped Pb(In1/2Nb1/2)O3 (PIN)–PMN-PT.
These doped crystals exhibit exceptional piezoelectric properties, including high d33 values and dielectric constants. Nonetheless, further research is needed to explore other doping elements and find materials that strike a balance between high Tr-t/Tc and d33 values.
Fig. 1. The overview of the design of the cUSBr-Patch.
(A) Schematic of a cUSBr-Patch on the body. (B) Exploded view of the cUSBr-Patch to illustrate its four main components: a soft fabric bra to serve as a familiar intermediary layer, a honeycomb patch as the outside layer to provide structure and guidance of the 1D array, the tracker to hold and rotate the 1D array, and the single crystal–based 1D phased array. (C) Schematic of breast quadrants and the positions of circular regions that align with the patch openings and circular holes in the bra. (D) Schematic of the honeycomb patch with six main openings (blue areas). The red dashed line indicates the specific trace for the 1D array scanning. The light green areas indicate additional nine hexagonal sections for imaging. (E) Photo of the honeycomb patch with the array and tracker. (F) Photo of the tracker. (G and I) Photos of the tracker rotating clockwise from 0° to 120°, demonstrating its capability for a 360° rotation. (J) Photo of the fabric bra with circular holes on a healthy human subject. Circular holes are designed to specifically serve as openings for the array to have intimate integration with skin and align with patch openings. (K) Photo of the patch attaching on the bra without mechanical delamination. (L) Photo of an easy-to-operate scanning. Scale bars, 1 cm (E) to (I) and 2 cm (J) to (L).
Challenges in Breast Imaging with Conformable Ultrasound
Large-area, deep tissue imaging poses mechanical challenges, especially when imaging the human breast, given its variable geometry and deformability. Ultrasound is critical in breast cancer diagnosis and treatment, as it allows for meaningful imaging of dissimilar breast tissue presentations. The current ultrasound breast imaging technologies, such as handheld ultrasonography (HHUS) and automated breast ultrasound (ABUS), have their limitations. HHUS relies heavily on the expertise of the technician, while ABUS experiences poor skin contact due to the use of a liquid medium and stationary, bulky machines in hospitals.
Proposed Solution: Conformable Ultrasound Breast Patch (cUSBr-Patch)
To address the challenges in breast imaging, the researchers propose a conformable ultrasound breast patch (cUSBr-Patch) that comprises a one-dimensional (1D) phased array and an easily operable nature-inspired patch design. This patch offers large-area, deep tissue scanning and multi-angle, repeatable breast imaging, overcoming the limitations of conventional ultrasound imaging technologies.
The researchers synthesized a Yb/Bi-doped PIN-PMN-PT single crystal with superior properties, including high d33, ɛr, and a suitable phased transition temperature. A 1D phased array transducer consisting of 64 elements with an operational frequency of 7.0 MHz was fabricated, exhibiting promising acoustic performance with increased imaging depth, contrast sensitivity, and resolution. This technology shows potential in detecting early-stage breast tumors.
Comprehensive in vitro experimental studies demonstrate that the cUSBr-Patch can provide accurate and reproducible imaging on different phantoms. The patch’s nature-inspired honeycomb design includes a scanning trace and 360° rotation capabilities, allowing the 1D array to fully cover the entire breast surface and obtain multiangle image reconstruction from different views. This breakthrough technology overcomes imaging artifacts caused by poor positioning or lack of contact, making it a novel and noninvasive method for monitoring dynamic changes in breast tissue.
Piezoelectric-based conformable ultrasound breast imaging has the potential to revolutionize healthcare monitoring, particularly in breast cancer diagnosis and screening. By incorporating advanced piezoelectric materials and a nature-inspired patch design, the proposed cUSBr-Patch offers superior acoustic properties and reliable imaging capabilities.
This technology allows for a full image of the breast with easy operation, providing a cost-effective, accessible, and user-friendly approach for early assessments of breast anomalies.
reference link : https://www.science.org/doi/10.1126/sciadv.adh5325