Development of High Frequency and Wideband PMUTs Toward Skincare Assessment Applications

Skin measurement plays a crucial role in skincare assessment. High-frequency ultrasound showing benefits of non-invasiveness, high-resolution and large penetration, which would significantly improve the accuracy for skincare assessment. However, commercial piezoelectric ultrasound probes of high cost and large size are lack of comfort and ease of use. In contrast, traditional high-frequency piezoelectric micromechanical ultrasound transducers (PMUTs), with smaller-sized but relatively narrow bandwidth, in not suitable for high accuracy ultrasound imaging. In this study, we present a PMUT design with a large bandwidth for skin evaluation. By reducing the array spacing, both the bandwidth and the sensitivity of the PMUT device were simultaneously enhanced successfully. The 10MHz PMUT with a bandwidth of 40.7% was flexibly packaged as an ultrasound patch with a thickness of less than 1 mm. Experiments on simulated skin models and ex vivo porcine ear tissues demonstrated that the developed PMUT achieved an axial resolution of 0.2 mm and measured tissue layer thicknesses consistent with actual values, which confirmed the feasibility to measure the skin thicknesses. This study lays the foundation for developing high-performance high-frequency PMUTs, which would significantly advance the development of wearable ultrasound sensing devices. [2025-0161]