Pencil-and-paper graphene sensor offers low-cost solution for healthcare and agriculture

In a significant step towards affordable and sustainable sensor technology, researchers at Gauhati University have developed a flexible, low-cost sensor using simple materials such as pencil, paper and graphene. The innovation holds promise for wide-ranging applications in hospitals, farms and wearable health monitoring.

The research, led by Dr Hemen Kumar Kalita of the Department of Physics along with his PhD scholars Rajnandan Lahkar and Biswajit Dehingia, addresses the growing demand for economical and scalable sensors. Unlike conventional sensors that rely on rigid substrates, expensive metals like gold or platinum, and complex manufacturing processes, the newly developed sensor is designed to be simple, flexible and cost-effective.

The team created a graphene-based capacitive sensor on a paper substrate by drawing interdigitated electrodes using ordinary pencils. Graphene oxide was used as the active sensing material. This novel approach eliminates the need for costly metals, cleanroom facilities and chemical-intensive fabrication, resulting in a lightweight, environmentally friendly and disposable sensor suitable for large-area applications.

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The study, published in the international peer-reviewed journal ACS Applied Electronic Materials, reports that the sensor exhibits exceptionally high sensitivity to humidity and moisture, with a response exceeding 1,500 per cent at high relative humidity levels. This marks a notable improvement over existing paper-based and flexible sensors, which often face limitations such as low sensitivity or single-function capability.

The sensor has been successfully demonstrated across multiple real-world applications, including soil moisture measurement, detection of plant drought stress, monitoring of human breathing patterns, skin moisture tracking, non-contact proximity sensing and smart diaper wetness detection. The ability to perform diverse functions using a single, low-cost device underscores the technological significance of the research.

The study was supported by the Department of Science and Technology (DST) through the INSPIRE programme, the Early Career Research Award and the DST-PURSE initiative, which provided essential funding, materials and manpower support for the project.

Researchers say the work highlights how locally adaptable, low-cost methods can be used to develop high-performance sensor technologies with potential impact across healthcare and agriculture sectors.