Signal amplifier developed for bioinstrumentation

Researchers from Osaka University have developed what they claim is the world’s thinnest and lightest differential amplifier for bioinstrumentation. Their work has been described in the journal Nature Electronics.

Conventionally, bioinstrumentation circuits for health care and medical use have consisted of hard electronic devices, such as silicon transistors. However, when soft biological tissues, such as skin, come into contact with hard electronic devices, they tend to become inflamed. Therefore, monitoring of biosignals in everyday life over a long period of time proved difficult.

Flexible amplifiers with organic transistors integrated into them are designed to eliminate the discomfort felt by users; however, conventional organic amplifiers mainly have a single-ended structure that cannot distinguish the target biosignals from disturbance noise. This makes it difficult to monitor biosignals with low noise levels, such as brain waves and cardiac sounds of a foetus.

The Osaka research group developed their own flexible bioinstrumentation circuit by integrating organic transistors on a thin and flexible plastic film with a thickness of 1 μm. The developed circuit is a signal-processing circuit called a differential amplifier.

Compared with conventional single-ended amplifiers, the flexible differential amplifier developed in the study not only amplifies very weak biopotential but also reduces disturbance noise. The group demonstrated that the differential amplifier can be applied to human instrumentation and realise real-time monitoring of electrocardiac signals with reduced noise levels.

This achievement is expected to lead to the monitoring of various weak biosignals in everyday life in addition to electrocardiac signals, without subjecting users to discomfort. This will enable the collection of long-term bioinstrumentation data, improving disease detection, treatment efficiency, patient monitoring and more.

Image caption: The organic differential amplifier is extremely lightweight and thin, and can be attached onto soft skin without causing any discomfort to the user.

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