A Soft Resistive Acoustic Sensor Based on Suspended Standing Nanowire Membranes with Point Crack Design

Abstract

An artificial basilar membrane (ABM) is an acoustic transducer that mimics the mechanical frequency selectivity of the real basilar membrane, which has the potential to revolutionize current cochlear implant technology. While such ABMs can be potentially realized using piezoelectric, triboelectric, and capacitive transduction methods, it remains notoriously difficult to achieve resistive ABM due to the poor frequency discrimination of resistive‐type materials. Here, a point crack technology on noncracking vertically aligned gold nanowire (V‐AuNW) films is reported, which allows for designing soft acoustic sensors with electric signals in good agreement with vibrometer output—a capability not achieved with corresponding bulk cracking system. The strategy can lead to soft microphones for music recognition comparable to the conventional microphone. Moreover, a soft resistive ABM is demonstrated by integrating eight nanowire‐based sensor strips on a soft trapezoid frame. The wearable ABM exhibits high‐frequency selectivity in the range of 319–1951 Hz and high sensitivity of 0.48–4.26 Pa−1. The simple yet efficient fabrication in conjunction with programmable crack design indicates the promise of the methodology for a wide range of applications in future wearable voice recognition devices, cochlea implants, and human–machine interfaces.

Enhanced Performance of a Soft Strain Sensor by Combining Microcracks with Wrinkled Structures

“…Over the past decades, various strain sensors have been reported to achieve high sensitivity or wonderfully stretchable range, indicating efficient applications for blood pressure measurements, muscle movements, and cardiac pacing in various motion scenes. [ 20–29 ] For these types of complex applications onto irregular curvilinear surfaces, it is critical that the strain sensors must be shape‐adaptive, highly sensitive, and portable enough to meet the demand for stretching with the objects during the test process as well as guaranteeing accuracy of the measurement results at the same time.…”

“…On the other hand, hierarchical wrinkles formed on the soft elastic substrates have a gratifying ability to deform, meeting the demand for adapting to the irregular surfaces of objects and variable external stress. Furthermore, due to the intrinsic reliability of gold material, the performance and lifetime can easily lift the difficulty for its application in complex environments, such as under the skin, in the eyes, in the intestine, in the heart, and inside other places in the body, [ 20–22,25,26 ] where a high‐temperature, acidic, or alkaline environment exists. Compared to strain sensors based on a traditional structure, a great improvement of stretchability is achieved, which broadens the maximum strain value to 40% of the original length.…”

Metamaterials-Enabled Sensing for Human-Machine Interfacing

“…Cochlear implants can convert sound signals into electrical stimuli for the auditory nerves, but most of the cochlear implants are rigid, thus sometimes cause wearing discomfort and nerve injury. Gong et al designed a suspended local-crack nanowire metamaterial acoustic sensor to detect the out-of-plane sound signals with rather-good static and dynamic acoustic frequency discrimination capability up to 3000 Hz [ 117 ]. The acoustic metamaterial sensor prototype is shown in Figure 8 a, which is soft and durable.…”

“…( a ) Photograph of the soft nanowire-based acoustic metamaterial membrane, schematic of the experimental setup of music detection, and acoustic sensor output (curve) and the STFT analysis of the background in response to notes with different music scale. Reproduced with permission from [ 117 ]. Copyright 2020, Wiley.…”

Smart Stretchable Electronics for Advanced Human–Machine Interface

“…[1][2][3][4][5] An HMI is a bidirectional communication interface that is divided into human-to-machine (H2M) systems and machine-to-human (M2H) systems. H2M devices include sensors for measuring command signals such as touch, [6][7][8] voice, [9,10] and gesture, [11][12][13][14] which allow for better system control, and measurement systems for measuring electrophysiological signals such as electromyography (EMG), electrocardiography (ECG), and electrooculography (EOG). [15][16][17][18][19] M2H devices provide electrical, thermal, visual, or mechanical feedbacks that simulate various sensations.…”