A-360 Reproducible Graphene Sensor with Desiccated Biology
Authors: Aithal S , Gupta S , Kumar A , Kumawat R , Duong K , Ho N , Liu R , Warden J , Le S , Ho D H 
Published: September 2023

Abstract

Background
Graphene, a two-dimensional material composed of carbon atoms, has garnered significant attention for its potential application in biosensors due to its unique electrical properties. Despite its promising attributes, however, the non-reproducible nature of graphene biosensors has hindered their widespread commercialization. This issue arises from the difficulty in obtaining a clean graphene layer due to: photoresist such as PMMA residues that effect the performance of graphene; etching process which affect the physical and chemical properties of graphene; variation in the coating of bio-receptors on to graphene. All these issues affect reliable and accurate sensor performance. These challenges have made it difficult for graphene biosensors to reach their full potential as commercial products and have limited their widespread adoption. Hememics has developed a unique process for synthesizing and fabricating graphene-based biosensors. This represents a major breakthrough in the commercialization of graphene-based biosensors and will likely lead to widespread adoption of these devices in the medical and biotechnology industries.

Methods
HemChip™ contains multiple sensor areas that are coated with ultra-sensitive graphene. Using Hememics’ unique proprietary process, the graphene layer is functionalized with bioreceptors such as aptamers and stabilized with HemSol™ to allow room temperature storage. The relative difficulty of stabilizing aptamers on a hydrophobic graphene substrate has been overcome by using HemSol™ to secure its structure during dry storage. Each sensor on the biochip allows independent functionalization with a bioreceptor. These sensors coated with bioreceptors are freeze-dried and stored in a sealed pouch at room temperature until use.

Results
We have tested over 2000 samples using our modified process. The functionality of the graphene-based biosensor is evaluated by measuring the distribution of Dirac points. The results show that the distribution follows a Gaussian distribution with a median of 80 mV and a very narrow spread of approximately 35 mV. This indicates that the majority of the Dirac points are tightly clustered around the median value of 80 mV. Furthermore, one standard deviation of the Dirac points fall within the range of 50 mV to 120 mV. In contrast, the standard published process of producing graphene-based biosensor shows a much wider distribution of Dirac points, ranging from 250–1500 mV.

Conclusion
Hememics has developed a production process for making graphene-based biosensors with desiccated detection biology that deliver repeatable performance data. The results of the Dirac point distribution demonstrate the high precision and accuracy for the functionalized biosensors. This combined with the ability to mass produce the biosensor, make graphene-based biosensors an attractive molecular and immuno-based detection tool. Additionally, the results suggest that the Hememics process can be adapted to produce functional graphene-based biosensors for wide ranging bio detection applications.