There is a demand to minimise the size of sound detectors and to functionally integrate them into wearable electronics, with the ability to generate and detect sound within a single device. An international group of researchers has fabricated an intelligent artificial throat device using laser-induced graphene that can perform both of these functions.

There are many people in this world who cannot speak, whether it be due to disease, accidents or otherwise. There have been many technologies developed to help people who cannot speak, but by expressing themselves as alternatives to speaking- such as converting eye movements into language expressions. Such technologies have a high cost and are complex in nature. As such, they are not widely used in everyday life.

Many people who cannot speak actually have the ability to hum, cough and scream. These are classified as unclear noises to most people, but the ability to transform these noises into controlled and useful language expressions is what has driven this research. Outdated technology found in traditional sound sources and detectors have a resonant peak and limited flexibility- something that is unsuitable for wearable electronics.

Many ideas were offered as how to create such a novel and functional device including piezoresistive materials, elastic polymers and other thermoacoustic graphene-based ideas. However, many of these prototypes suffer from poor sensitivity, complex fabrication processes, low yield and high cost. The main driving force for the failure of these prototypes was their inability to work as both a sound source and sound detector.

Laser scribing is an established technique that has contributed to the fabrication of many graphene-based devices which allows for large scale and customisable patterns to be developed. However, the preparation is complex so a method of converting graphene oxide and polyimide (PI) into a porous graphene sheet, i.e. laser-induced graphene (LIG), was utilised.

The researchers have developed a one-step process that fabricates a low-cost and wearable LIG artificial throat. The LIG throat exhibits a high performance for both generating and detecting sounds. It is the LIG within the device, which possesses fantastic thermoacoustic and piezoresistive properties, that enables the functional integration of emitting and detection within a single device.

As a sound source, the device can generate a wide-band sound source with a frequency of 100 Hz to 40 kHz. A thinner LIG layer is known to produce a higher sound pressure level. The device also has a broad frequency spectrum due to resonance-free oscillations from the sound sources.

As a detector, the artificial throat device shows a unique response towards different kinds of sounds and throat vibrations. The device can recognize vocal activities such as coughing, humming and screaming at different tones and volumes, through the mechanical vibrations of the throat cords with fine repetition. This recognition is performed with clear distinction due to the differentiation of their specific waveforms. It also has the capability to recognise words and sentences. The different volumes and/or frequencies can be transformed into controllable and predesigned sounds. The excellent mechanical properties of the device also allow the device to be capable of voice recognition.

The artificial throat has potential applications to assist the disabled. The device’s ability to generate volume and frequency controls by the detection of different hums, allows the device to turn a meaningless hum into a controllable sound. This feature provides many practical applications. The simple one-step process makes the device a commercial and scalable prospect. There are many applications where the device could be implemented in the future, including voice control, voice recognition and wearable electronics, to name a few.

Source:

Tao L-Q., Tian H., Liu Y., Ju Z-Y., Pang Y., Chen Y-Q., Wang D-Y., Tian X-G., Yan J-C., Deng N-Q., Yang Y., Ren T-L., An intelligent artificial throat with sound-sensing ability based on laser induced graphene, Nature Communication, 2017, 8, 14579

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