Closely Packed Stretchable Ultrasound Array Fabricated with Surface Charge Engineering for Contactless Gesture and Materials Detection

Abstract

Communication with hand gestures plays a significant role in human‐computer interaction by providing an intuitive and natural way for humans to communicate with machines. Ultrasound‐based devices have shown promising results in contactless hand gesture recognition without requiring physical contact. However, it is challenging to fabricate a densely packed wearable ultrasound array. Here, a stretchable ultrasound array is demonstrated with closely packed transducer elements fabricated using surface charge engineering between pre‐charged 1–3 Lead Zirconate Titanate (PZT) composite and thin polyimide film without using a microscope. The array exhibits excellent ultrasound properties with a wide bandwidth (≈57.1%) and high electromechanical coefficient (≈0.75). The ultrasound array can decipher gestures up to 10 cm in distance by using a contactless triboelectric module and identify materials from the time constant of the exponentially decaying impedance based on their triboelectric properties by utilizing the electrostatic induction phase. The newly proposed metric of the areal‐time constant is material‐specific and decreases monotonically from a highly positive human body (1.13 m2 s) to negatively charged polydimethylsiloxane (PDMS) (0.02 m2 s) in the triboelectric series. The capability of the closely packed ultrasound array to detect material along with hand gesture interpretation provides an additional dimension in the next‐generation human‐robot interaction.

Curved and Annular Diaphragm Coupled Piezoelectric Micromachined Ultrasonic Transducers for High Transmit Biomedical Applications

“…However, the main purpose of the study is to enhance the transmit efficiency not the bandwidth, which is the dominant obstacle in the applications using continuous waves or modulated waves such as therapy [4,5], biomedical particle manipulation [6][7][8], and neural stimulation [10]. Moreover, we would like to address the possibility of enlarging the bandwidth for the CAC-pMUT array, which is important for medical imaging [1-3] and gesture recognition [9] applications. It could be achieved by placing cells of different sizes together in a fluid acoustic medium and utilizing the large damping effect of the acoustic medium to merge the multiple resonance peaks to achieve an increased bandwidth [15].…”

“…In the past decades, ultrasonic transducers have gained increasing popularity in applications such as medical imaging [1][2][3], invasive or non-invasive therapy [4,5], biomedical particle manipulation [6][7][8], gesture recognition [9], and neural stimulation [10]. The high transmit performance of the transducers is key for these applications to achieve enhanced pressure output with good signal-to-noise contrast (SNC).…”