A silicon flow cell for optical detection in miniaturized total chemical analysis systems

Microfabricated Silicon Flow-Cell for Optical Monitoring of Biological Fluids

“…In this case, the refractive indices were 1.333 for water and 3.49 for silicon respectively. 4 By the Fresnel Equations 7 , the reflectivity at the water-silicon interface at normal incidence was calculated to be 0.200. However, a light beam exiting from an optical fiber diverges at an angle defined by the numerical aperture of the optical fiber and the refractivity at the phase boundaries (Fig.…”

“…The module is simple, easy to fabricate, having a volume in the microliter range, and has a collection efficiency of light much higher than in an earlier study. 4 Although a micromachined glass detection cell with good limits of detection for absorbance and fluorescence measurements has been developed for capillary electrophoresis 5 , the alignment of the optical fibers in the cell is complicate, and is thus unsuitable for use in a disposable manner. In this study, the detection method is based on reflection-absorption measurements.…”

Fabrication of multilayer systems combining microfluidic and microoptical elements for fluorescence detection

“…The detection modes in these systems can be as varied as ultraviolet (UV)-absorbance [1]- [3], refractive index measurements [4], [5], electrochemical detection [6]- [8], or laser-induced fluorescence detection (LIF) [9], [10]. Due to its selectivity and high sensitivity [11]- [13], LIF is one of the preferred detection techniques on microchemical chips.…”

“…The SNR (power of the background-corrected signal/noise power) and SNR in dB are given by [25] SNR (1) and SNR (2) where and are the average fluorescence and background signal, respectively, and and are the variances of and , respectively. The total noise is hence calculated as the sum of the variances and .…”

More than technology alone

“…(1) In the early 1990s, authors such as Manz et al, Harrison et al, and Verpoorte et al, 2,3,6 had already touched upon the promise of mTAS devices for use outside the laboratory. For medical devices this was soon linked up with the ability to measure (bio)chemical substances when and wherever needed, a process known as Point-of-Care testing.…”