Digital Biosensing by Foundry-Fabricated Graphene Sensors

Jolie Nokes,Jeremy Lerner,Amy Walker,Francie Barron,Deng Pan,Mitchell Lerner,Brett R. Goldsmith,Savannah Afsahi,Angela Shue,Jayla Kyaw,Yingning Gao,Lauren Locascio

doi:10.1038/s41598-019-38700-w

Abstract

The prevailing philosophy in biological testing has been to focus on simple tests with easy to interpret information such as ELISA or lateral flow assays. At the same time, there has been a decades long understanding in device physics and nanotechnology that electrical approaches have the potential to drastically improve the quality, speed, and cost of biological testing provided that computational resources are available to analyze the resulting complex data. This concept can be conceived of as “the internet of biology” in the same way miniaturized electronic sensors have enabled “the internet of things.” It is well established in the nanotechnology literature that techniques such as field effect biosensing are capable of rapid and flexible biological testing. Until now, access to this new technology has been limited to academic researchers focused on bioelectronic devices and their collaborators. Here we show that this capability is retained in an industrially manufactured device, opening access to this technology generally. Access to this type of production opens the door for rapid deployment of nanoelectronic sensors outside the research space. The low power and resource usage of these biosensors enables biotech engineers to gain immediate control over precise biological and environmental data.

Highlights

TheoryClosest to the graphene channel, the salts in solution will form a well-organized and well-understood layer on top of the surface countering any difference in charge between the surface and the liquid
The Donnan effect region extends beyond the Debye length, extending through the thickness of an ion-permeable membrane immobilized to the surface
The voltage in the bulk liquid is controlled by conventional electrochemical means

Summary

Background

Closest to the graphene channel, the salts in solution will form a well-organized and well-understood layer on top of the surface countering any difference in charge between the surface and the liquid. Α is a very low 0.02, but in practice this value is increased by the presence of oxides and nitrides used in device fabrication; α values for practical graphene transistors are around 0.3736–38 This term is combined with the thermal voltage (φth), about 26 mV, and pH shift from a neutral surface (ΔpH) to produce the equivalent gate voltage due to pH. Any charges or dipoles leading to a net charge within that immobilized ion permeable layer (cx) will require an extra accumulation of a counter-ion within the layer to maintain charge neutrality This difference in the concentration of ions between the bulk solution (cs) and that in the immobilized protein layer creates a Donnan potential[8,39]. This additional potential enables sensing beyond the Debye screening length,[31,33,40] and has been demonstrated repeatedly with graphene biosensors[6,15,20,24,41]

Results

Discussion

Methods