Michael Berger over at Nanowerk is profiling the development by a Singaporean team of a palm-size biosensor. The lab-on-a-chip device employs highly localized surface plasmon resonance (LSPR) technology and cuts out the standard spectrum analyzer for a set of four pulsing light emitting diodes.
Neuzil [Dr. Pavel Neuzil, researcher at the Institute of Microelectronics in Singapore] explains that the typical reflection spectra of an in-house-fabricated LSPR chip exhibits absorption peaks at 555 nm for water and 645 nm for ethanol. “Measuring only the intensity of the reflected light at a few selected wavelengths could lead to a calculation of the peak shift” he says. “In fact, a LSPR system with high reproducibility could even be based on the amplitude of the reflected light intensity at a selected wavelength. The consequence of this is significant as this would allow replacement of the spectrum analyzer and subsequent signal processing scheme by a single source of monochromatic light and a photodiode as detector. The resulting photocurrent output could then be converted into a voltage by an operational amplifier with a resistor in a feedback loop (I/V converter) and detected by a voltmeter.”
The two researchers have started this work accidentally. They were conducting an advanced lithography experiment for researchers from a sister institute using a method called lift-off: silicon wafers with 200 mm diameters were covered with light sensitive material (photo resist) and exposed by deep UV light creating a regular pattern of 150 nm diameter holes in the photoresist. The next step was gold deposition over the photoresist and final step was supposed to be photoresist removal by dissolving in a suitable solvent such as acetone together with the gold above the photoresist.
Read the rest at Nanowerk…
Article in Analytical Chemistry: Palm-Sized Biodetection System Based on Localized Surface Plasmon Resonance