Flexible Thin-Film Thermoacoustic Speaker Using Carbon Nanotubes for Wearable Sensors

Overview

The modern dynamic speaker requires a mechanically-actuated diaphragm, rare-earth magnets, and rigid voice coils, which causes them to be bulky and inflexible. However, current developments in wearable electronics such as AMOLED display screens has created a demand for ultra-thin, bendable speakers that can integrate into these devices - but current alternative technologies are inefficient and difficult to manufacture. Here, a novel sound generation method called the thermoacoustic (TA) phenomenon is shown in multi-walled carbon nanotubes (CNTs), and a transparent, flexible, and lightweight speaker is created. This project aims to standardize a simple fabrication process for a flexible speaker, optimize the speaker based on criteria of sensitivity and performance range, and use the TA speakers as a wearable sensor. In this study, simple two part speakers are fabricated by hand with copper electrodes and a CNT sheet. Furthermore, two methods of optimization: encapsulation and layer-stacking are successfully demonstrated. By sandwiching the CNT sheet in between two plastic membranes, the membrane vibrates and its natural resonance frequency is used to fine-tune sound output and create more robust sound production, while layer-stacking is used to decrease the overall resistance of the speaker. To test the effects of these optimization methods, the sensitivity of the device is measured across multiple frequencies. The combination of both optimization methods results in a 774% increase in average sound output and a 935% increase in peak sound output compared to the original CNT speaker. This reaches levels superior to alternative thin-film speakers by an order of magnitude and reaches outputs seen in modern speakers. Finally, emission of ultrasonic waves is used to create a novel distance mapping tool via echolocation. TA sound generation offers a superior alternative method to integrate transducers into wearable electronics and will be important for their future development.

Competition history

• AJAS 2019 Category not listed

Related projects

Closest projects by meaning, across every fair and year in the corpus.

Browse more like this

• All Materials Science and Engineering projects
• AJAS Materials Science and Engineering projects
• Every AJAS 2019 project