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Khalifa University Team Develops Green Humidity Sensors for Wearable Electronics

30 Oct 2023

A new fabrication technique for wearable humidity sensors developed from graphene oxide and paper cellulose fiber provides enhanced efficiency and a reduced environmental impact. 


A team of researchers from Khalifa University’s System on Chip Lab (SoCL) has developed a novel humidity sensor from environmentally friendly paper cellulose fiber and graphene oxide matrix. Their sensor, which is also biocompatible, is designed for use in various wearable electronic devices and has already been employed in several applications, including non-contact proximity sensing, environmental humidity detection, and human respiration detection. The applications showcase the sensors broad potential. 


Postdoctoral Fellow Dr. Muhammad Umair Khan, Research Scientists  Dr. Yawar Abbas and Dr. Heba Abunahla, Associate Professors Dr. Moh’d Rezeq and Dr. Anas Alazzam, Assistant Professor Dr. Nahla Alamoodi, and Prof. Baker Mohammad, published the details of this work in the journal Sensors and Actuators B: Chemical


“Our work represents a significant milestone in developing inexpensive and eco-friendly humidity sensors, from paper and carbon nanomaterials, which are abundant in nature and biocompatibile,” said Dr. Alamoodi.


Humidity sensors are used in a wide variety of industrial applications, from environmental monitoring and defogging in vehicles to wearable technology and food logistics. However, making these sensors more sensitive, responsive and reliable is a research priority. Research focusing on using green and eco-friendly materials for humidity-sensing devices is particularly important. 


Wearable electronics often use humidity-sensing materials placed on flexible substrates, including polyimide and other polymers, but these substrates come with challenges: There’s a risk of separation during deformation, affecting their performance, and there are also environmental concerns as many of these polymer materials aren’t biodegradable. 


Using eco-friendly materials in device manufacturing can combat these challenges, mitigating environmental impact and ensuring high performance. 


Paper cellulose is the most abundance natural polymer. Its mechanical stability, high hydrophilicity, and water insolubility make it a promising candidate for humidity sensors, but cellulose by itself cannot offer electrical conductivity. The research team integrated reduced graphene oxide, a carbon-based conductive material. Their novel fabrication method enhances the device’s detection range, flexibility and stability, as the combination of paper cellulose fiber and graphene oxide shows improved sensitivity and a rapid response time to changes in humidity. 


“We used normal office paper, which is mainly composed of cellulose,” said Dr. Alamoodi. “This improves sustainability as our device can also be produced from recycled office paper. 


“Carbon-based conductive materials offer high conductivity and stability for humidity sensors in paper-based composite or layered structures,” said Dr. Alamoodi. “Previous methods have used graphene and carbon-based materials in combination with cellulose, but the resulting materials cracked during deformation due to the incompatibility of the stiff conductive filler and the flexible paper. We introduced a novel fabrication process to make a flexible and green humidity sensors, without the need for conductive fillers. Our method is simple and inexpensive and results in a three-layer sensor device.”


The KU team’s strategy is straightforward and effective, producing a high-performance and environmentally friendly humidity sensor from a paper cellulose fiber and graphene oxide matrix. Their sensor can detect moisture from human breath, fingertip proximity and moisture detection in open environments, suggesting it has potential for use in agro-industrial enterprises and healthcare systems.

Jade Sterling
Science Writer
30 October 2023