Pyrex cover

We have designed, manufactured and tested a prototype that may be applied in thermal control of electronic devices. It was fabricated from a silicon substrate and a Pyrex cover, serving as both an insulator and a window through which flow patterns and boiling phenomena could be observed. A number of parallel triangular micro-channels were etched in the substrate. The heat transferred from the device was simulated by different types of electrical heaters that provided uniform and non-uniform heat fluxes, defined here respectively as constant and non-constant values... 

The test module consisted of inlet and outlet manifolds that were jointed to the test chip (Fig. 6.20). The tested chip with heater is shown in Fig. 6.21. It was made from a square shape 15 x 15mm and 0.5 mm thick silicon wafer, which was later bonded to a 0.53 mm thick Pyrex cover. On one side of the silicon wafer 26 microchannels were etched, with triangular shaped cross-sections, with a base of 0.21 mm... 

In the study by Hetsroni et al. (2006b) the test module was made from a squareshaped silicon substrate 15 x 15 mm, 530 pm thick, and utilized a Pyrex cover, 500 pm thick, which served as both an insulator and a transparent cover through which flow in the micro-channels could be observed. The Pyrex cover was anod-ically bonded to the silicon chip, in order to seal the channels. In the silicon substrate parallel micro-channels were etched, the cross-section of each channel was an isosceles triangle. The main parameters that affect the explosive boiling oscillations (EBO) in an individual channel of the heat sink such as hydraulic diameter, mass flux, and heat flux were studied. During EBO the pressure drop oscillations were always accompanied by wall temperature oscillations. The period of these oscillations was very short and the oscillation amplitude increased with an increase in heat input. This type of oscillation was found to occur at low vapor quality. 

Fabrication was done by photolithography and deep reactive ion etching (DRIB). The catalyst was inserted by sputtering. Such a prepared microstructure was sealed with a Pyrex cover. The bonded micro device was placed on a heating block containing four cartridge heaters. Five thermocouples monitored temperature on the back side. A stainless-steel clamp compressed the device with graphite sheets. 

Catalyst bed width depth length volume 25.55 mm 500 pm 400 pm 5.1 pi Operating temperature 550 °C (with Pyrex cover) 1000 °C (with Si cover)... 

Powdered single crystals of 1 (ca. 20 mg) were sandwiched between two Pyrex cover glasses and placed in a polyethylene bag, which was irradiated with a 400-W high-pressure mercury lamp for 6 h (3 h for each side of the sample) in an ice-water bath. Out of seven carboxamides examined, la, le and lg showed intramolecular photocycloaddition in solid state to give the [4+4] cycloadducts 2a, 2e, and 2g in an almost quantitative yield after complete conversion, and If gave 2f in 9% yield. 

The flow of leukocytes was studied in square capillaries fabricated on a Si chip, and sealed with a PDMS or Pyrex cover plate. This capillary size (cross section of 4 pm2) is similar to the diameter of a human blood capillary, but is less than both the average diameter of a leukocyte cell (10 pm) and its nucleus (6 pm). Figure 8.32 shows the difference in the flow behavior of two leukocytes (possibly neutrophils) [1175]. Deformation-induced release of ATP from erythrocytes in PDMS channels was studied. The released ATP was detected by chemiluminescence using the luciferin/luciferase system [169]. 

REACTION CELL. The reaction cell was made of a silicone rubber gasket sandwiched between two pyrex cover slides. The cell was pressed against the flat face of a cylindrical heater, which was proportionally controlled to within 1°C. Two small holes were bored near the top of the rubber gasket for inserting a thermocouple and for filling the cell. 

Figure 5.19 PolySi-based nano-tips including Pyrex cover plate and a via hole for easy connection to capillary tubing, and dedicated holder for user-friendly handling. (A) Scheme of the integrated polySi-based nano-tips. (B) Image of an integrated microTAS. (C) Mechanical holder dedicated to the nano-nib microTAS for easy and watertight connection to capillary tubing.

Biochemical analysis on nanoliter scale is precisely carried out by micrototal analysis system (pTAS) which consists of microreactors, microfluidic systems, and detectors. Performance of the pTAS depends on micromachined and electrochemically actuated micropump capable of precise dosing of nanoliter amounts of liquids such as reagents, indicators, or calibration fluids [28]. The dosing system is based on the displacement of the liquid from a reservoir which is actuated by gas bubbles produced electrochemically. Electrochemical pump and dosing system consist of a channel structure micro-machined in silicon closed by Pyrex covered with novel metal electrodes. By applying pulsed current to the electrodes, gas bubbles are produced by electrolysis of water. The liquid stored in the meander is driven out into the microchannel structure due to expansion of gas bubbles in the reservoir as shown in Fig. 11.8. 

In conclusion, if a Pyrex cover is used to close silicon microchanneis, the silicon walls of the microchanneis tend to work at constant tempera-mre with an imposed constant heat flux on the contrary, the Pyrex side can be considered adiabatic. Due to the high ratio between the thermal conductivity of the silicon and of the fluid (in this case kjk = 247) and its small hydraulic diameter, the microchannel can be conveniently studied as a long duct under a classical HI thermal boundary condition (theoretically valid for kJk = oo). On the other hand, when a silicon cover is used to close the microchannel, all the boundaries can be considered as isothermal (see Fig. 3b) it is possible to use the HI thermal boundary condition, with the four sides at an imposed uniform temperature. 

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