Benito-Lopez, F.

Berg, A. van den

Egberink, R.J.M.

Gardeniers, J.G.E.

Hermes, D.C.

Reinhoudt, D.N.

Tiggelaar, R.M.

Verboom, W.

van den Berg, A.

NARCIS 

Fabrication and mechanical testing of high-pressure glass microreactor chips

University of Twente Research Information

FABRICATION AND MECHANICAL TESTING OF HIGH-PRESSURE GLASS MICROREACTOR CHIPSRoald Tiggelaar1, Fernando Benito-López2, Dorothee Hermes1, Richard Egberink2, Han Gardeniers1, Wim Verboom2, David N. Reinhoudt2 and Albert van den Berg1MESA+ Institute for Nanotechnology, University of Twente,P.O. Box 217, 7500 AE Enschede, The Netherlands1: BIOS Lab-on-a-Chip Group, 2: Supramolecular Chemistry and Technology GroupHigh-pressure conditions can have a positive effect on stereoselectivity, conversion and yield1, however work in this area has been limited due to the requirement of special lab equipment. Due to their small characteristic dimensions microreactors are suitable for performing chemical reactions that require extreme conditions without extensive safety precautions2. Here we discuss the design, fabrication and testing of glass chips for high pressure applications, and show that pressures up to ca. 700 atms are feasible with such chips..Microreactor: Design & FabricationIn Fig. 1 a picture of the microreactor is shown. The chip has two inlets for introduction of pressurized fluids. In the following channel (cross-section 70 μm x 30 μm, length 13.5 mm) mixing of the fluids takes place as well as the chemical reaction. This channel  connects to a narrow channel (cross-section 20 μm x 5 μm; length 177 mm), which acts as a hydraulic resistance that ensures a virtually constant, high pressure in the reaction zone of the chip. The high-resistance channel ends in a wider zone that is at atmospheric conditions. Figure 1: Picture of chip for high-pressurechemistry (20  15  2.2 mm). Legend:1 & 2 inlets, 3 reaction zone, 4 fluidic resis-tance zone, 5 expansion zone, 6 outlet.	The chips were made by means of wet chemical etching and powder blasting in two separate glass wafers (Borofloat 33), and direct bonding. The inlets and outlet were created by powder blasting and/or etching with 25 vol.% hydrofluoric acid (HF). The different channel-zones were etched using HF. After dicing of the package, capillary fused silica fibers were connected to the chips using 2-component glue (Araldite Rapid or Loctite).Experiments: Strength of Glass MicroreactorsDuring preliminary experiments it turned out that chip-failure at pressures above 80 bars frequently occurred at one of the inlets. Therefore, different inlet-configurations (geometry, roughness) and bonding procedures (anodic, direct) were implemented in dedicated test-chips to investigate which design results in the highest working pressures. In Fig. 2 cross-sectional views of these designs are shown (light-gray: Borofloat, dark-gray: Si).   1	      2	    3	  4	    5				Figure 2: Different configurations of inlets (cross-sectional side views).A short description of the fabrication process of each configuration in Fig. 2:1: 	Powder blasted inlet (smoothened by HF); direct bonding (600 ºC for 1h); use of fibers with 360 µm outer diameter.2:	Identical to 1, but: HF-etched capping in top wafer (5 μm deep); prebonding and apply force of 11 tons on waferstack for 1h; direct bonding (600 ºC for 1h).3:	Identical to 2, but: use of fibers with 110 µm outer diameter.4:	Identical to 3, but: no capping; anodic bonding to silicon wafer.5:	HF-etched inlet (tubular structure in bottom and top wafer); prebonding and apply pressure of 11 tons on waferstack for 1h; direct bonding (600 ºC for 1h); use of fibers with 110 µm outer diameter.The maximum pressure (pmax) that each inlet configuration could resist with CO2 (l) as medium is shown in Fig. 3 (destructive tests). From this graph it is concluded that:Figure 3: Maximum pressures obtained with CO2 (l) for inlets shown in Fig. 2.	Inlets with small cross-sections are stronger (and more reliable) than large ones;Circular and smooth inlets - fully HF etched structures - are by far the best: pmax exceeds 690 bars;Loctite should be used as glue for the fibers; For small cross-sections there is a trend that a sharper inlet-design results in a higher pmax.Maximum pressure tests were also performed with H2O. Although the pmax-values were 30-50 bars lower for every inlet-design, the overall conclusion is identical.Conclusion and outlookWith the described microreactor chips working pressures above 200 bars can be achieved easily. In Fig. 4 an application is shown: a glass chip is used to study the carbamic acid formation of N-benzylmethylamine with CO2. From the NMR-spectra it can be seen that product is indeed formed for 200 bars (at 100 ºC), whereas for a low pressure (10 bar, 100 ºC) no product formation was observed.References1 G. Jenner, Tetrahedron, 53, 2669 (1997).2 K.F. Jensen – AIChE J., 45, 2051 (1999).	Figure 4: 1H-NMR spectra of high-pressure products (indicated by arrows) obtained on glass chips. 

English

http://purl.utwente.nl/publications/63781

Fabrication and mechanical testing of high-pressure glass microreactor chips

Abstract

Similar works

Full text

Available Versions

NARCIS

University of Twente Research Information