Issue link: https://iconnect007.uberflip.com/i/1236528
APRIL 2020 I PCB007 MAGAZINE 67 micromechanical, and microoptics onto the same substrates allows automated device con- trol, which reduces human error and operation costs. 3. Chem-Bio Detectors and Sensors Detectors, sensors, and electrodes can be ChemFET and BioFET C-MOS devices with special membranes or diffusions to make them sensitive to chemical or biological molecules. The sensors and electrodes are electrical ele- ments that are sensitive to various chemical or biological molecules, plated with gold, sil- ver, platinum, palladium, etc., and their salts (Figure 5). 4. Microfluidic Chips A microfluidic chip is a set of microchannels etched or molded into a material (glass, sili- con, or polymer, such as PDMS). Microchan- nels form the microfluidic chip connected in order to achieve the desired features (mix, pump, sort, control bio-chemical environment, etc.). Networks of microchannels are connect- ed to the outside by inputs (inlets) and outputs (outlets) pierced through the chip (interface between the macro and micro world). LoC Materials Over the years, several materials have been developed for use with LoC. It started in the late 1990s with silicon, as the microelectron- ics industry developed various methods of mi- cromachining silicon (MEMS) for accelerom- eters for airbag sensors. From silicon wafers, the materials branched out to glass and then polymers. The most recent interest has been in PCBs and the use of various paper materials. Silicon and glass have several advantages for fabricating an LoC, while being the most ex- pensive. Polymers and especially PCBs are a new choice because of various materials avail- able and the integration of electronics and vari- ous printing technologies. While paper is com- ing into focus for research, its use is only just beginning. Table 1 lists several characteristics of each of these materials. 1. Silicon-based Silicon started the LoC point-of-care (PoC) diagnostic uses. Figure 6 shows one of the first on the market—the Agilent 2100 Bioanalyzer System—for DNA, RNA, serum protein, and infectious disease analysis. Figure 6: Agilent Technology has been in- volved in the life sciences since 1995. Their "nanolab chips" are used to analyze DNA, RNA, SARS, and other infectious disease pro- teins [2] . 2. Glass-based Glass is a lower cost material if electrical components and circuitry are not required. Glass can be fabricated into microchannels and deposited with many substances such as gels and coating. The glass device seen in Figure 7 is an Agilent 3100 Bioanalyzer Automated LC/ MS that comes in numerous forms to separate Figure 5: P-MOS Bio-FET sensors channels and photodetectors [2] ; (a) Reference electrode; (b) Ag/AgCl plating on a PCB; (c) plated PCB [3] .