Tunable and Highly Sensitive Graphene‐based Sensor
July 10, 2015 | EPFLEstimated reading time: 3 minutes
Researchers at EPFL and ICFO have developed a sensor made from graphene to detect molecules such as proteins and drugs. This is one of the first devices exploiting the unique electronic and optical properties of graphene for a practical application.
Many areas of fundamental research are interested in graphene owing to its exceptional characteristics. It is made of one layer of carbon atoms, which makes it light and sturdy, and it is an excellent thermal and electrical conductor. Despite its apparently limitless potential, however, few applications have been demonstrated to date. Scientists at EPFL’s Bionanophotonic Systems Laboratory (BIOS) together with researchers from the Institute of Photonic Sciences (ICFO, Spain) have now added another one. They have harnessed graphene’s unique optical and electronic properties to develop a reconfigurable highly sensitive molecule sensor. The results are described in an article appearing in the latest edition of the journalScience.
Focussing light to improve sensing
The researchers used graphene to improve on a well-‐known molecule-‐detection method: infrared absorption spectroscopy. In the standard method, light is used to excite the molecules, which vibrate differently depending on their nature. It can be compared to a guitar string, which makes different sounds depending on its length. By virtue of this vibration, the molecules reveal their presence and even their identity. This “signature” can be “read” in the reflected light.
This method is not effective, however, in detecting nanometrically-‐sized molecules. The wavelength of the infrared photon directed at a molecule is around 6 microns (6,000 nanometres – 0.006 millimeters), while the target measures only a few nanometres (about 0.000001 mm). It is very challenging to detect the vibration of such a small molecule in reflected light.
There is where graphene comes in. If given the correct geometry, the graphene is able to focus the light on a precise spot on its surface and “hear” the vibration of a nanometric molecule that is attached to it. “We first pattern nanostructures on the graphene surface by bombarding it with electron beams and etching it with oxygen ions,” said Daniel Rodrigo, co‐author of the publication. “When the light arrives, the electrons in graphene nanostructures begin to oscillate. This phenomenon, known as ‘localized surface plasmon resonance,’ serves to concentrate light into tiny spots, which are comparable with the dimensions of the target molecules. It is then possible to detect nanometric structures.”
Reconfiguring graphene in real time to see the molecule’s structure
There is more to it. In addition to identifying the presence of nanometric molecules, this process can also reveal the nature of the bonds connecting the atoms that the molecule is composed of.
When a molecule vibrates, it does not give off only one type of "sound." It produces a whole range of vibrations, which are generated by the bonds connecting the different atoms. Returning to the example of the guitar: each string vibrates differently and together they form one musical instrument. These nuances provide information on the nature of each bond and on the health of the entire molecule. “These vibrations act as a fingerprint that allow us to identify the molecule; such as proteins, and can even tell their health status” said Odeta Limaj, another co-author of the publication.
In order to pick up the sound given off by each of the strings, it has to be possible to identify a whole range of frequencies. And that is something graphene can do. The researchers “tuned” the graphene to different frequencies by applying voltage, which is not possible with current sensors. Making graphene's electrons oscillate in different ways makes it possible to “read” all the vibrations of the molecule on its surface. “We tested this method on proteins that we attached to the graphene. It gave us a full picture of the molecule,” said Hatice Altug.
A big step closer to using graphene for molecule sensing
The new graphene-‐based process represents a major step forward for the researchers, for several reasons. First, this simple method shows that it is possible to conduct a complex analysis using only one device, while it normally requires many different ones. And all this without stressing or modifying the biological sample. Second, it shows graphene’s incredible potential in the area of detection. “There are many possible applications,” said Altug. “We focussed on biomolecules, but the method should also work for polymers, and many other substances,” she added.
Suggested Items
Warm Windows and Streamlined Skin Patches – IDTechEx Explores Flexible and Printed Electronics
04/26/2024 | IDTechExFlexible and printed electronics can be integrated into cars and homes to create modern aesthetics that are beneficial and easy to use. From luminous car controls to food labels that communicate the quality of food, the uses of this technology are endless and can upgrade many areas of everyday life.
Book Excerpt: The Printed Circuit Assembler’s Guide to... Factory Analytics
04/24/2024 | I-Connect007 Editorial TeamIn our fast-changing, deeply competitive, and margin-tight industry, factory analytics can be the key to unlocking untapped improvements to guarantee a thriving business. On top of that, electronics manufacturers are facing a tremendous burden to do more with less. If you don't already have a copy of this book, what follows is an excerpt from the introduction chapter of 'The Printed Circuit Assembler’s Guide to... Factory Analytics: Unlocking Efficiency Through Data Insights' to whet your appetite.
Listen Up! The Intricacies of PCB Drilling Detailed in New Podcast Episode
04/25/2024 | I-Connect007In episode 5 of the podcast series, On the Line With: Designing for Reality, Nolan Johnson and Matt Stevenson continue down the manufacturing process, this time focusing on the post-lamination drilling process for PCBs. Matt and Nolan delve into the intricacies of the PCB drilling process, highlighting the importance of hole quality, drill parameters, and design optimization to ensure smooth manufacturing. The conversation covers topics such as drill bit sizes, aspect ratios, vias, challenges in drilling, and ways to enhance efficiency in the drilling department.
Elevating PCB Design Engineering With IPC Programs
04/24/2024 | Cory Blaylock, IPCIn a monumental stride for the electronics manufacturing industry, IPC has successfully championed the recognition of the PCB Design Engineer as an official occupation by the U.S. Department of Labor (DOL). This pivotal achievement not only underscores the critical role of PCB design engineers within the technology landscape, but also marks the beginning of a transformative journey toward nurturing a robust, skilled workforce ready to propel our industry into the future.
Winner of The Science Show Rakett 69 Receives Incap Scholarship
04/24/2024 | IncapThe winner of the Rakett 69 science show, Andri Türkson, who stood out as an electronics enthusiast, received a scholarship from Incap Estonia, along with an internship opportunity in Saaremaa.