Micro-patterned bull’s-eye improves SERS sensitivity

Nov. 4, 2014
To maximize the number of molecules delivered to the detection area of a substrate when performing surface-enhanced Raman spectroscopy (SERS), a team of researchers has developed a micropatterned bull’s-eye structure that uses superhydrophobic (water-repelling) action.

To maximize the number of molecules delivered to the detection area of a substrate when performing surface-enhanced Raman spectroscopy (SERS), researchers at Harvard University (Cambridge, MA) and the École polytechnique fédérale de Lausanne (EPFL; Switzerland) have developed a micropatterned bull’s-eye structure that uses superhydrophobic (water-repelling) action. That is, a water droplet containing gold colloids, for example, is attracted to the bull’s-eye center, concentrating the colloids as it dries. Later, analyte molecules delivered via another water droplet adhere tightly to the colloids, increasing the number of molecules probed in a small area and correspondingly magnifying the SERS signal. For example, Rhodamine 6G can be detected at molar concentration levels as small as 10-15.

Rather than using expensive electron-beam lithography (EBL) and focused-ion-beam (FIB) milling methods, the SERS bull’s-eye was fabricated in silicon using simple optical lithography. A hexagonally oriented array of micropillars (3 μm radius, 15 μm height) spaced 20 μm apart is interspersed among 24 radial microfins with the same dimensions but length of 2 mm to create the 4-mm-diameter superhydrophobic structure with a 50-μm-diameter circular platform at the center. A water droplet is pinned in the center based on Cassie–Baxter modeling equations that deliver optimized contact angles for the patterned and smooth surfaces of the silicon substrate. The method significantly improves SERS sensitivity while simultaneously reducing the amount of gold needed to perform a SERS measurement. Contact Wuzhou Song at[email protected].

Sponsored Recommendations

Download New Product Development Strategies White Paper

March 27, 2025
Discover the importance of new product innovation, different process methods, and best practices for optimizing your company’s strengths.

Manufacturing Considerations for Tolerancing Aspheres

March 13, 2025
Understand the critical factors in manufacturing aspheres and how Lacroix Optics ensures precise tolerancing in every optical component.

Explore Our Videos: Insights into Precision Optics

March 13, 2025
Get an inside look at Lacroix Optics with our collection of informative videos showcasing our capabilities, innovations, and processes.

Optical Assemblies: Reliable and Precise Solutions

March 13, 2025
Ensure your optical system works seamlessly with Lacroix Optics' custom optical assemblies. Discover the precision and reliability we bring to every project.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!