Graphene FET Tests Multiple Diseases On Chip at Once
Archer Materials’ latest device uses ultra-thin graphene to detect multiple diseases on one chip. The next goal: a reconfigurable biochip.
Aiming for a comprehensive lab-on-chip solution, Archer Materials has announced a new biochip using graphene FETs (gFETs). Since its discovery in 2004, graphene's lattice structure has demonstrated numerous unique advantages, several of which can be used in transistor fabrication to create ultra-sensitive devices.
gFETs include an ultra-thin graphene layer. Used as a conductive layer, this material is sensitive enough to allow engineers can detect an ionic solution's content. Image used courtesy of Graphenea
gFETs are particularly popular in biosensing applications since they can provide insight into patient health through molecular-level interactions between the graphene and the target bio-particles. Archer recently submitted a biochip graphene sensor to a commercial foundry in an MPW run. The company revealed that this solution can test for multiple diseases on one chip.
Since graphene-enabled technologies such as gFETs are still relatively new, this article dives into the details behind gFET fabrication and gives readers context on how graphene could be used to detect multiple diseases using a single chip.
gFETs are remarkably similar to other field-effect transistors, such as MOSFETs, but differ in the material used as the conductive medium. While MOSFETs use materials such as silicon to send current from drain to source, gFETs use a graphene layer only tens of micrometers thick.
The thin layer of graphene imparts numerous benefits, such as thermal and electrical conductivity, and also considerably improves the device's sensitivity to external factors. As such, labs often use gFETs to characterize adjacent fluids because graphene's inherent molecular-level sensitivity can easily detect pathogens.
gFETs use a single graphene channel as the conductive medium to control instead of silicon in the case of MOSFETs. Image used courtesy of Graphenea
To accommodate liquid samples for testing, Archer first developed “wettable” gFETs that can withstand contact with liquid materials. Archer then expanded these gFETs to test for single diseases, with the latest development aiming to test for multiple diseases on a single chip.
While graphene offers numerous benefits compared to traditional silicon electronics, it has its fair share of drawbacks. Chief of these is a complex fabrication process, with gFETs requiring extremely thin graphene layers to function correctly.
Typical graphene processes use chemical vapor deposition (CVD) to “grow” graphene on a substrate, after which it can be carefully removed. A lithographic process then deposits the metal contacts of the gFETs to connect to external circuitry. Lithography can also be used to modify graphene layers to create desired shapes.
An example biochip shows the interdigitated fingers used with multiple channels to achieve detection in a fluidic system. Image used courtesy of Archer
Implementing a similar process, the Archer gFET devices use single-device multiplexing, where each gFET sensor can be read individually to test for multiple diseases on the same chip. Archer hopes to eventually offer a real-time tuning feature for gFET parameters, potentially making gFET sensors a reusable solution.
Archer expects both the MPW and whole wafer runs to be available for delivery by the end of 2023. At this point, the company can validate and evaluate the chips to give Archer a better understanding of how the chips will perform in a practical environment.
Extending Beyond Biochips
While gFETs find much use in biosensing applications, the benefits of graphene transistors can extend to RFIC designs or high-speed switching. Ultimately, however, the scope of gFETs depends on whether fabricators can reliably incorporate graphene devices with silicon.
Despite this uncertainty, graphene FETs present clear advantages, with more expected to come to light after the delivery of Archer’s latest shuttle runs.