Improving the signal visibility of optical-disk-drive sensors by analyte patterning and frequency-domain analysis

Abstract

One limitation of using compact disks (CDs) and optical disk drives for sensing and imaging of analytes placed on a CD is the fluctuations in the voltage signal from the disk drive generated while reading the data on the CD. In this study, we develop a simple, low-cost strategy for sensing and identification using CDs and optical disk drives that spectrally separates contributions to the voltage signal caused by an analyte intentionally placed onto the CD and that caused by the underlying data on the CD. Analytes are printed onto a CD surface with fixed spatial periodicity. As the laser beam in an optical disk drive scans over the section of the CD containing the analyte pattern, the intensity of the laser beam incident onto the photodiode integrated into the disk drive is modulated at a frequency dependent on the spatial periodicity of the analyte pattern and the speed of the optical-disk-drive motor. Fourier transformation of the voltage signal from the optical disk drive yields peaks in the frequency spectrum with amplitudes and locations that enable analyte sensing and identification, respectively. We study the influence of analyte area coverage, pattern periodicity, and CD rotational frequency on the peaks in the frequency spectrum associated with the patterned analyte. We apply this technique to discriminate differently-colored analytes, perform trigger-free detection of multiple analytes distributed on a single CD, and detect at least two different, overlapped analyte patterns on a single CD. The extension of this technique for sensing and identification of colorimetric chemical reagents is discussed.

Enhancing the sensitivity in optical biosensing by striped arrays and frequency-domain analysis

“…Therefore, by using the intensity of the resulting peak as analytical magnitude, noise can be efficiently discriminated in order to analyze biointeractions in a more sensitive fashion. Schaefer and Chau explored this strategy to discriminate voltage fluctuations in an ink-based optical system [13]. Hereinafter, we introduce for the first time FDA for biochemical analysis, describe and discus the key parameters for its implementation, and experimentally demonstrate the performance improvement provided by this methodology.…”

Automated, portable, low-cost bright-field and fluorescence microscope with autofocus and autoscanning capabilities

“…Optimal focusing of the lens is achieved by fine, micrometerscale adjustments of the vertical and horizontal lens position using the coil actuator. In recent years, there has been increasing interest in using the optical and mechanical components integrated into optical pickup units for imaging and sensing applications [11][12][13][14][15][16]. Here, we adapt an optical pickup unit by replacing the laser diode with an LED and the photodiode with a standard web camera (Logitech Webcam C160) that interfaces with a computer through a USB connection.…”