Chemical mixing and reaction apparatus

An integral structure is provided for chemical processing, particularly high-speed mixing and chemical reacting, in which a plurality of laminae are joined together and having inlet and outlet ports connected by a plurality of intersecting channels formed therethrough which accommodate the passage of one or more chemicals, said laminae comprising a material selected for compatibility with the one or more chemicals, the channels being formed so that chemicals are combined at intersections therein at sufficient angles of attack and shear rates so that chemical reactions are not limited by mass transfer. Chemicals are introduced through the inlet ports and processed along the channel, with desirable product withdrawn through the outlet ports. The laminae are selected from material of groups III, IV or V of the Periodic Table. Processes of manufacture of the apparatus and processes utilizing the apparatus are also disclosed herein.

FIELD OF THE INVENTION 
This invention relates to an integrated chemical processing apparatus, 
adapted for use with high-speed chemical reactions, which can be 
incorporated into a larger integral structure of multiple chemical 
processing units or an integrated system. More particularly, the present 
invention is directed to chemical processing apparatus characterized by 
improved rapid mixing of chemicals passing therethrough, by enhanced 
safety of operation, and by reduced capital investment. 
BACKGROUND OF THE INVENTION 
To achieve efficient chemical processing, it is necessary to precisely 
control a number of processing parameters, such as temperature, pressure, 
mixing conditions, exposure of reactants to catalyst material, exposure of 
reactants to products and/or byproducts and exposure of reactants to 
actinic radiation. Certain chemical reactions are particularly difficult 
to perform in an optimal manner because the chemical reactions occur very 
quickly, sometimes before the reactants are completely mixed together. 
Certain non-stoichiometric portions of the partially mixed reactants may 
cause reaction products other than those desired to be produced. 
Conventional chemical processing equipment typically holds a relatively 
large volume of materials and consequently has a relatively large volume 
to surface area ratio, and are thus particularly ill-suited for high speed 
chemical reactions. Different portions of the reactant materials contained 
within such processing equipment are more likely to be exposed to 
different histories of conditions. In the case of a conventional tank 
reactor, for example, when reactants are introduced they are typically 
added in separate streams, usually at controlled rates, and are then mixed 
together. The so-called T-mixer has been used to mix incoming streams 
together before they enter a reactor tank. For chemical reactions that 
occur rapidly, i.e., typically in less than one second, insufficient 
mixing may have occurred, even with use of the T-mixer, before the 
reaction is well established. Portions of the incompletely mixed mixture 
may be starved of one or the other reactant and undesired secondary 
reactions may occur which produce undesired byproducts. 
Rapid stirring of the reactants may reduce this mixing history difference, 
but will not eliminate it. As a result of the nonhomogeneous mixing 
history, different portions of the reactants may chemically react 
differently. Undesired reactions may occur in portions of the reactants 
that cause localized heating in these different portions. This localized 
heating may accelerate undesired reactions. This may result in the 
production of undesired waste products, which may be hazardous and/or 
which must be properly disposed of. In extreme situations, reaction rates 
may accelerate to uncontrollable levels, which may cause safety hazards, 
such as potential explosions. 
If, however, the volume in each reactant stream being mixed is 
substantially reduced, then the speed of mixing of the reactants may be 
greatly increased to substantially improve the control of homogeneity of 
mixing history of the reactants. 
It has been recognized that a high degree of flow turbulence enhances the 
ability to rapidly mix two or more reactants together. Rapid mixing is 
known to be important for rapid chemical reactions. A high degree of 
turbulence is also known to enhance heat transfer as well as mixing rates. 
Thus a structure having both a low contained volume and a high degree of 
flow turbulence is particularly advantageous for precise control of 
high-speed chemical reactions. 
Mixer assemblies having highly turbulent flow have been constructed by 
machining the desired passages and chambers in metal plates, using 
conventional metalworking techniques, and then assembling the plates into 
a stack and either clamping the stack together or permanently joining the 
stack, as by welding or soldering. An example is U.S. Pat. No. 3,701,619. 
Structures formed using conventional machine tool techniques cannot 
economically achieve volume to surface area ratios that are very low. The 
materials of construction of conventional chemical processing apparatus, 
such as steel and specialty iron alloys, furthermore may be subject to 
corrosion and wear, may have undesirable effects on catalytic activity, or 
may "poison" a catalyst. 
It is an object of the present invention to provide a chemical processing 
unit that mixes reactants in a rapid and efficient manner, such that 
chemical reactions are not limited by mass transfer considerations. The 
present invention provides the capability to integrate one or more 
mixing/reaction units with control elements into a larger integrated 
chemical processing system to meet the needs of a specific high-speed 
chemical reaction. A feature of the present invention is that it can be 
economically used in the laboratory, to make a range of precise sizes of 
mixing/reaction units, to perform the basic chemical reactions for 
determining the optimum operating parameters. Commercial production 
volumes may then be readily achieved by replicating the mixing/reaction 
units and operating them in parallel in a larger integrated chemical 
processing system. 
Advantages of the present invention, when used in a larger integrated 
chemical processing apparatus, include the elimination of many 
interconnections and joints, thereby reducing the potential for leaks. 
These and other objects, features and advantages will become better 
understood upon having reference to the following description of the 
invention. 
SUMMARY OF THE INVENTION 
There is disclosed and claimed herein an apparatus for use in an integral 
structure for chemical mixing and reacting of one or more chemicals, 
comprising a plurality of laminae joined together and having a plurality 
of intersecting channels formed therethrough which accommodate the passage 
of one or more chemicals. The laminae comprise a material selected for 
compatibility with the one or more chemicals, the channels being formed so 
that chemicals are combined at intersections therein at sufficient angles 
of attack and shear rates so that chemical reactions are not limited by 
mass transfer considerations. Moreover, the shear rate is sufficient to 
disrupt boundary layer formation. The channels are arranged such that two 
or more channels are positioned at a point of intersection to form an 
angle of attack of from 20 to 160 degrees, preferably from 70 to 110 
degrees, and most preferably about 90 degrees. 
The apparatus of the invention may be prepared according to the process of 
the invention. The process comprises first, processing a plurality of 
laminae each having a top portion and a bottom portion and a desired 
thickness, sufficient to form desired pathways thereon or therethrough. 
The laminae are then stacked and bonded together in precise alignment to 
develop channels that intersect at a desired angle of attack. 
In the process for preparing the integral structure, the pathways on facing 
surfaces of adjacent laminae generally form passages through the structure 
in the plane of the laminae having the desired cross-sectional areas. In a 
preferred embodiment, the ration of the length of any straight channel 
portion to the hydraulic diameter is less than 8. These planar passages 
are connected with each other and with passages orthogonal to the plane of 
the laminae which pass through one or more laminae to form passages having 
the desired overall three-dimensional shapes. 
The apparatus of the present invention may be used in a method for mixing 
and reacting of chemicals. The method comprises: (a) introducing one or 
more chemicals into channels of the above-described structure; (b) 
directing the chemicals to traverse the channels; (c) coordinating 
traversal at a traversal rate so that angles of attack and shear rates are 
sufficient to insure that chemical reactions are not limited by mass 
transfer considerations; and (d) withdrawing reacted product from the 
channels of the structure. 
The invention can be more fully understood from the following detailed 
description thereof in connection with accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention is characterized by small channels of complex 
three-dimensional shapes which: (1) can create a high degree of flow 
turbulence that enhances rapid mixing and heat transfer; (2) intersect 
with other channels in a shearing fashion at a predetermined angle of 
attack; (3) have a very low volume to surface area ratio that minimizes 
temperature gradients and further enhances heat transfer; and (4) controls 
residence time of materials therein, to achieve more precise temperature 
control, and a more uniform temperature history, for every portion of the 
entire volume of reactants mixed and reacted. Channels small enough that 
they will not allow the propagation of a flame may be readily formed and 
thus can be used to safely react potentially explosive chemical reactants. 
The channels may measure as small as about 10 micrometers in cross 
section. 
Throughout the following detailed description, reference characters between 
1 and 99 refer to overall features of the invention. That is, these 
features may only be apparent on joinder of adjacent laminae. For example, 
in FIG. 7 chamber 50M is comprised of chamber 250M on laminae 200 and 
chamber 350M on laminae 300. Laminae are numbered 100, 200, 300, and 
specific features on each respective lamina are numbered 101 to 199, 201 
to 299, etc. with the last two digits corresponding to the overall feature 
of the invention. The suffix letter "V" is used to designate interlamina 
vertical pathways, also known as "vias" through the structure. Similarly, 
suffix "M" indicates a manifold chamber within a manifold; suffixes "S" 
and "T" indicate straight and turning portions of pathways. Suffixes 
comprising a hyphen and numeral (-1, -2, etc.) are used to designate parts 
of specific elements, such as individual branches of the branched 
manifolds. A capital letter and number are appended to the reference 
character to designate elements of an array (e.g., mixer 64A2 of array 
64). Numerals enclosed in curved braces {} designate crystal planes in a 
crystalline material (e.g., {100}). 
Referring to FIG. 1, there is shown an apparatus 10 exemplary of the 
present invention. This apparatus 10 is comprised of a plurality of 
laminae 100, 200, 300 fused together to form an integral structure. One or 
more inlet ports (here, inlet ports 20 and 24 are shown) enable the flow 
of reactants into the apparatus and one or more outlet ports (here, outlet 
ports 30 and 34 are shown) enable the flow of the resulting reaction 
products out of the apparatus. It is to be appreciated that the inlet 
ports 20 and 24 and outlet ports 30 and 34 do not necessarily have to be 
positioned only through lamina 100 as shown but may extend through all 
three laminae (e.g., outlet port 34 in FIG. 4). These elements could be 
arranged to meet the integral structure at the side of a lamina, for 
example (not shown). The laminae may be comprised of either the same or 
different materials. The laminae (also known as wafers) 100, 200, 300 
preferably are comprised of materials from groups III, IV or V of the 
Periodic Table, silicon being the most preferred material. If desired one 
or more of the laminae may be comprised of an alternate material, such as 
ceramic, a glass material such as Pyrex or other compatible materials. 
FIG. 2 shows the top surfaces of the three laminae 100, 200, 300 and FIG. 3 
shows the bottom surfaces of the three laminae 100, 200, 300 which are 
used to form the apparatus of FIG. 1. Operative features of the apparatus 
shown in FIGS. 2 and 3 are: two distribution manifolds 40, 44 formed by 
pathways in the bottom surface of lamina 100 and the top surface of lamina 
200; an array 60 of mixer/reaction chambers represented by a 
series/parallel arrangement of T-mixers 62 and intersecting-channel mixing 
elements 64 formed by corresponding pathways in the bottom surface of 
lamina 100 and the top surface of lamina 200; a fork-shaped collection 
manifold 50 formed by corresponding pathways in the bottom surface of 
lamina 200 and the top surface of lamina 300. 
In sectional views of FIGS. 4 and 5 the vertical scale is exaggerated for 
clarity of illustration. Although the laminae of the apparatus are fused 
into an integral structure when completely fabricated, for clarity of 
illustration the interfaces between the laminae are shown in FIGS. 4 and 
5. 
In FIGS. 4 and 5, which illustrate typical flow passages in the interior of 
the structure, the vertical pathways 20V, 24V, 30V, 34V which connect 
respectively with the inlet ports 20, 24 and outlet port 30 in lamina 100 
and outlet port 34 in outer laminae 100 and 300, are typically formed by 
grinding or drilling through the lamina. 
In FIG. 4 three passages 40-1, 40-2, 40-3, which are branches of 
distribution manifold 40 and three passages 44-1, 44-2, 44-3, which are 
branches of distribution manifold 44 are formed in the top surface of 
lamina 200. Five passages 50-1, 50-2, 50-3, 50-4, 50-5, which are branches 
of collection manifold 50, are respectively formed by corresponding mirror 
image pathways 250-1, 250-2, 250-3, 250-4, 250-5 (see also FIG. 7) in the 
bottom surface of lamina 200 and pathways 350-1, 350-2, 350-3, 350-4, 
350-5 (FIG. 7) in the top surface of lamina 300. 
In FIG. 5 the central axis of a third horizontal passage 50-3 (see also 
FIG. 7), which comprises the center branch of a 5-branch collection 
manifold 50, lies in the plane of the sectional view. The horizontal 
passage 50-3 is formed by corresponding mirror image pathways, 
respectively pathway 250-3 (FIG. 7) in the bottom surface of lamina 200 
and pathway 350-3 (FIG. 7) in the top surface of lamina 300. The passages 
which comprise the 5-branch collection manifold 50 in the exemplary 
apparatus are formed using an etching technique. 
In FIG. 5 passages 160A, 160B, 160C, 160D, in combination with the branches 
40-1, 44-1; 44-1, 40-2; 40-2, 44-2; and 40-3, 44-3 of distribution 
manifolds 40, 44 (FIGS. 4 and 7) form an array of T-mixer structures 62 
whose operation will be subsequently described in conjunction with FIGS. 
6, 7. The passages 164 in the bottom surface of the lamina 100 and the 
passages 264 in the top surface of lamina 200 cooperate to form an array 
of mixers (sometimes referred to as mixing elements or mixing chambers) 
64, each of which comprises a plurality of intersecting channels (FIG. 6). 
At the left of FIG. 5 is vertical passage 20V, which extends through lamina 
100 to connect inlet port 20 with the common chamber 40M of distribution 
manifold 40. At the right of FIG. 5 is vertical passage 24V, which extends 
through lamina 100 to connect inlet port 24 with common chamber 44M of 
manifold 44. A third branch 50-3 of 5-branch manifold 50 is formed by 
corresponding mirror image pathways 250-3 and 350-3 (FIG. 7) in the bottom 
surface of lamina 200 and the top surface of lamina 300, respectively. 
Mixing chambers 64A3, 64B3, 64C3, 64D3 are visible in FIG. 5. 
FIG. 6 shows an arrangement of pathways that cooperate to form an array of 
mixer/reaction chambers 60 and a pair of distribution manifolds 40, 44. 
First distribution manifold 40 is comprised of common chamber 40M and 
branch passages 40-1, 40-2, 40-3. The chamber 40M is formed by the 
combination of chamber 140M, on the bottom surface of the first lamina 
100, and chamber 240M on the top of lamina 200. Also shown is the opening 
of vertical pathway 20V which connects input port 20 with the common 
chamber 40M. 
Second distribution manifold 44 is comprised of common chamber 44M and 
branch passages 44-1, 44-2, 44-3. The chamber 44M is formed by the 
combination of chamber 144M, on the bottom surface of the first lamina 
100, and chamber 244M on the top of lamina 200. Also shown is the opening 
of vertical pathway 24V which connects input port 24 with the common 
chamber 44M. 
A series of serpentine pathways 164 are formed on the bottom surface of the 
first lamina 100, which cooperate with corresponding serpentine pathways 
264 of lamina 200, to form the array of intersecting-channel mixing 
elements 64 (here, 64A5 formed from 164A5 and 264A5 in FIG. 6) of the 
mixer array 60. The mixer array 60 comprises multiple groups 60A (e.g., 
64A1-64A5), 60B, 60C, 60D of multiple parallel mixers 64. In the specific 
example shown, there are five mixers in each group, that are respectively 
designated 64A1, 64A2, 64A3, 64A4, 64A5 through 64D1, 64D2, 64D3, 64D4, 
64D5. FIG. 6 also shows chambers 40M and 44M, previously mentioned. 
Each mixer 64 is comprised of two serpentine pathways, a first pathway 164 
formed on the bottom of the first lamina 100 and a second pathway 264 
formed on the top of the second lamina 200. The first and second pathways 
are each comprised of a series of straight segments and turning segments 
connected together to form a continuous path. The first and second 
pathways are positioned on abutting surfaces with the segments 
longitudinally offset such that the corresponding turning segments 
intersect repeatedly. The mixer element 64 (as illustrated by mixer 
element 64A2) may be described as having a double serpentine path (best 
seen in FIG. 11). 
Four pathways 160A, 160B, 160C and 160D, cooperate respectively with 
branches 40-1, 40-2, 40-3 of manifold 40, branches 44-1, 44-2, 44-3 of 
manifold 44 and a first straight segment 264S of each serpentine pathway 
264 to form a series of T-mixers 62 (best seen in FIG. 8). Each first 
straight segment 264S thus connects each T-mixer 62 with each serpentine 
mixer 64 of mixer array 60. 
FIG. 7 shows the arrangement of pathways that cooperate to form a 
collection manifold 50. As seen in FIGS. 6 and 7, collection manifold 50 
is comprised of common chamber 50M and branch passages 50-1, 50-2, 50-3, 
50-4, and 50-5. The vertical pathways 64A1V, 64A2V, 64A3V, 64A4V, and 
64A5V connects the last segment of mixer 64A1, 64A2, 64A3, 64A4, 64A5 with 
the collection manifold branches 50-1, 50-2, 50-3, 50-4, and 50-5, 
respectively; the vertical pathway 64B1V, 64B2V, 64B3V, 64B4V, and 64B5V 
connects the last segment of mixer 64B1, 64B2, 64B3, 64B4, 64B5 with the 
collection manifold branches 50-1, 50-2, 50-3, 50-4, and 50-5, 
respectively; the vertical pathway 64C1V, 64C2V, 64C3V, 64C4V, and 64C5V 
connects the last segment of mixer 64C1, 64C2, 64C3, 64C4, 64C5 with the 
collection manifold branches 50-1, 50-2, 50-3, 50-4, and 50-5, 
respectively; and the vertical pathway 64D1V, 64D2V, 64D3V, 64D4V, and 
64D5V connects the last segment of mixer 64D1, 64D2, 64D3, 64D4, 64D5 with 
the collection manifold branches 50-1, 50-2, 50-3, 50-4, and 50-5, 
respectively. Vertical passage 30V connects collection manifold 50 with 
the outlet port 30 on the first side of lamina 100. Vertical passage 34V 
connects manifold 50 with both outlet ports 34 on the first side of lamina 
100 and the second side of the lamina 300, as best seen in FIG. 4. 
As best seen in FIG. 8, each pathway 160 cooperates with manifolds 40 and 
44 and a first straight segment of serpentine pathway 264 to form a 
T-mixer 62. This connects with a serpentine mixer 64, comprised of the 
multiple straight segments 264S and turning segments 264T. As also may be 
seen in FIG. 8 each portion of pathway 160, e.g., portion 160A-3 between 
manifold 44-2 and segment 264S1 and portion 160A-4 between manifold 40-2 
and segment 264S1, may be of a different cross-sectional size to provide 
the desired flow rate of each chemical being mixed. The number of straight 
and turning segments 164S, 164T and 264S, 264T and the cross-sectional 
size of each segment of 164 and 264 may be selected, according to the 
mixing requirements and flow characteristics of the chemicals being 
processed. 
As seen in FIG. 9 the serpentine pathways 164, 264 are comprised of 
straight segments designated with a suffix letter "S" (171S, 172S, 173S, 
174S, 175S, and 271S, 272S, 273S, 274S, 275S) and turning segments 
designated with a suffix letter T (171T, 172T, 173T, 174T, 175T, and 271T, 
272T, 273T, 274T, 275T). Corresponding turning segments (e.g., 171T, 271T) 
of pathways 164 and 264 intersect in a juxtaposed fashion at a ninety (90) 
degree angle of attack. By slightly offsetting the position of pathway 164 
relative to pathway 264 this angle of attack may be changed if desired. By 
rotating lamina 100 relative to lamina 200, and suitably altering the 
spacing of the straight segments (suffix S) and turning segments (suffix 
T), almost any desired angle of attack may be achieved. Angles of attack 
within the range of 20 degrees to 160 degrees may be readily realized, as 
is contemplated being within the scope of this invention. 
FIG. 10 shows an alternate arrangement of channels, which may be used in 
place of the arrangement shown in FIGS. 6, 8, and 9. FIG. 10 shows two 
channels 181, 182 in the bottom surface of lamina 100 that join at a point 
of intersection, traverse in a combined configuration as channel 183, are 
subsequently separated into two channels 184, 185, and then recombined as 
channel 186, separate into channels 187, 188. Channel 281 in the top 
surface of lamina 200 separates at a point of intersection into two 
channels 282, 283, which are then recombined as channel 284, are 
subsequently separated into two channels 285, 286, and then recombined as 
channel 287. Channel 181 intersects with channel 282 and channel 182 
intersects with channel 283 at predetermined angles of attack. Similarly 
channel 184 intersects with channel 282, channel 185 intersects with 
channel 283, channel 184 intersects with channel 285, channel 185 
intersects with channel 286, channel 187 intersects with channel 285, 
channel 188 intersects with channel 286. 
FIG. 11 depicts the channels of FIG. 9 in a somewhat simplified manner to 
better visualize the shape, relative position and intersections of the 
channels. As may be appreciated from FIGS. 9 and 11, two channels 
repeatedly intersect to form a double helix configuration, wherein a first 
channel 164 is comprised of straight segments and turning segments in a 
first plane, a second channel 264 is comprised of straight segments and 
turning segments in a second plane. 
Chemicals within a first channel are repeatedly subjected to the sequence 
of: (a) a turbulent left hand turn, (b) a turbulent left hand juxtaposed 
intersection with chemicals in a second channel, (c) a turbulent right 
hand turn, (d) a turbulent right hand turn, (e) a turbulent right hand 
juxtaposed intersection with chemicals in the second channel, (f) a 
turbulent left hand turn. 
FIG. 12 depicts the channels of FIG. 10 in a somewhat simplified manner to 
better visualize the shape, relative position and intersections of the 
channels. In this figure it can be seen that the two channels intersect at 
angles of attack. Each channel comprises two or more channels that join at 
a point of intersection, traverse in a combined configuration, are 
subsequently separated into two or more channels, and then subsequently 
rejoin. 
FIG. 13 (a)-(c) is a plan view of the channels of FIG. 9. It shows channel 
164 alone (FIG. 13(c)), channel 264 alone (FIG. 13 (a)), and 164 
superimposed with 264 (FIG. 13(b)). At the point of intersection of the 
channels a centerline 164C of channel 164 and a centerline 264C of channel 
264 are shown. The included angle .alpha. between these centerlines is 
defined as the "angle of attack" of the two channels. 
Multiple units of the chemical mixing and reaction apparatus can be used in 
sequence or in tandem. The incorporation of units in any number of 
sequential or tandem patterns is a design choice to be made by those 
skilled in the art and according to the desired chemical processing 
result. 
As seen in FIGS. 9 and 10 the particular angles of the channel walls 
produced at the turning sections (e.g., 171T) are due to the orientation 
of the crystal planes of the silicon. In the illustrated example each 
lamina comprises a silicon wafer which has the major planar surface of the 
wafer in the {100} crystal plane. The sides of the straight segments (e.g. 
171S, 271S) are aligned to be in the {110} crystal planes. When etched 
with an anisotropic etch, the major sides of the segments are bevelled 
from the vertical at a 57 degree angle and are in the {111} crystal 
planes. The outside corners between the straight segment 171S and the 
turning segment 171T, are not sharp right angles but are beveled by two 
so-called bevelling faceting planes, which are the {210} crystal planes, 
thus producing the bevelled corners which are best seen in FIGS. 9 and 10. 
FABRICATION OF THE APATUS 
The apparatus of the present invention is achieved by a multi-step 
fabrication process. First, a series of planar laminae or wafers, are 
processed to form desired patterns of pathways on one or both major 
surfaces of each lamina or through the thickness of the lamina. The 
laminae are then joined together to form a plurality of intersecting 
channels that accommodate the passage of chemicals. 
In the preferred embodiment of the figures, the laminae are arranged and 
precisely oriented to locate the channels in adjacent laminae. These 
channels may be continuous or discontinuous along each of the laminae. 
Discontinuous channels are continuously aligned between adjacent laminae 
sufficient to form a continuous pathway therethrough. A typical channel is 
comprised of straight segments and turning segments in a first plane, 
straight segments and turning segments in a second plane and transition 
segments between the two planes. The straight or turning segments of a 
channel may be formed as a groove or trough entirely within one lamina. 
When assembled this groove cooperates with the facing planar surface of 
the adjacent lamina to close the cross-section of the channel. This is 
best illustrated by the cross-sectional view of distribution manifold 40 
(seen as 40-1, 40-2, and 40-3) in FIG. 4. Mirror image grooves or troughs 
on facing surfaces of adjacent laminae may cooperate to form a channel 
having a symmetrical cross-section. This is best illustrated by the 
cross-sectional view of collection manifold 50 (seen as 50-1, 50-2, 50-3, 
50-4, and 50-5) in FIG. 4. The transition segments of the channels may be 
passages that pass through a lamina to connect a channel segment on a 
first lamina with another segment on a second lamina or with a 
distribution or collection manifold. This is best illustrated by the 
cross-sectional view of vertical pathways 64A3V through 64D3V in FIG. 5. 
Processing of Laminae 
The processing of the laminae to form pathways may be performed by a 
procedure selected from the group of: subtractive processes, additive 
processes, and forming processes. Subtractive processes comprise chemical 
etching, electrochemical machining (ECM), electrical discharge machining 
(EDM), laser ablation, drilling and cutting, abrasive grinding and single 
diamond point cutting (such as used to fabricate ceramic parts). Additive 
processes comprise deposition processes, such as electroforming, selective 
plating, chemical vapor deposition, stereo lithographic photoforming, and 
welding. Forming processes comprise molding, casting, and stamping. Wear 
resistant coatings, such as metalloid carbides, in the form of thin films, 
may be optionally deposited on the processed laminae before bonding. 
Materials of Construction 
Selection of lamina materials is based upon the material's compatibility 
with the chemicals to be mixed and reacted. As used herein "compatibility 
with the chemicals to be mixed and reacted" includes without limitation: 
resistance to chemical degradation; operating conditions, such as 
temperature and pressure; thermal conduction requirements; required 
features to be created in the lamina, including size, geometrical shape 
and precision; the sealability of the lamina material; and economic 
considerations. 
A variety of materials, may be used to construct the mixing/reaction units 
of the present invention. Crystalline materials that can be processed 
using photolithographic techniques may be used, especially when a 
mixing/reaction unit with extremely small cross-sectional passages are 
desired, for instance when gasses that react rapidly are to be processed. 
Such crystalline materials would typically include elements from groups 
III through V of the periodic table, for example silicon. Other compound 
materials, selected for their resistance to chemical attack, may be used 
to fabricate the laminae or may be used as coatings on the laminae. 
Ceramic materials may be used, such as silicon carbide, tungsten carbide, 
alumina and sapphire for instance using known molding, pressing and 
Sintering techniques, to form the laminae. Thin films may be deposited on 
the surfaces of the laminae, such as by chemical vapor deposition 
techniques, to improve resistance of the passages to chemical attack or to 
facilitate bonding of the laminae. Glass materials, such as fused quartz, 
pure silica glass and borosilicate glass, as well as composite materials, 
such as ceramic composites and polymeric composites may be used. 
For example, wafers similar to those used to fabricate semiconductor 
electronics components, such as single crystal silicon wafers, may be 
used. For such silicon wafers a combination of subtractive techniques may 
be used to form the passages. The laminae are subsequently stacked in 
precise alignment and joined together (as by bonding or clamping) into an 
integral structure. As illustrated in the example of FIG. 1, three laminae 
are joined as an apparatus. The laminae may be of identical or different 
materials. The outer laminae may be silicon or a protective material such 
as metal, ceramic, composite material or glass while the inner lamina 
would typically be silicon. If all the laminae are silicon, thermal fusion 
bonding is a preferred method of joining the laminae because the strength 
of the bond achieved approaches that of the laminae themselves. 
OPERATION OF THE APATUS 
Having reference to FIGS. 1-3, the two materials to be reacted flow into 
the unit through input ports 20, 24, through vertical passages 20V, 24V 
into distribution manifolds 40, 44 and into mixer array 60. Optional 
temperature control means (not shown) may be used to maintain the mixer 
array 60 at the desired temperature. The mixed material is collected in 
collection manifold 50 and passed through vertical passage 30V to the 
outlet port 30 or through vertical passage 34V to the outlet port 34. 
Additional microfabricated process control elements, such as proportional 
valves, pressure, temperature and flow sensors, may be incorporated with 
the structure of the present invention. These elements, when used with 
external controls could regulate the flow of reactants within the 
integrated chemical processing unit and thus control the residence time. 
Any rapid chemical process, such as hydrolysis, nitration, polymerization, 
and oxidation may be practiced using the integrated structure of the 
present invention. 
FABRICATION OF THE LAMINAE 
In the preferred embodiment, most steps of the fabrication process 
generally correspond to known semiconductor processing techniques for 
silicon wafers. The photo-tools for the patterns for each side of each 
wafer are prepared using well known computer-aided-design techniques. 
Already polished silicon wafers, having the {100} crystal plane and other 
orientations on the major surfaces may be purchased from commercial 
sources. The polished wafers are first cleaned using a well-known general 
cleaning technique, such as the "RCA process". An oxide film is grown on 
the wafer using well-known standard techniques. A nitride layer is 
deposited over the oxide layer using a known chemical vapor deposition 
method. The nitride layer protects the oxide layer from attack by the etch 
used to etch the silicon. A photoresist is applied, following the 
directions of the photo resist manufacturer, using the well-known spin 
coating technique. 
The desired pattern is formed by first masking the wafer with a photo-tool 
having an image of the desired pattern, which is precisely aligned with 
the crystal planes of the wafer. Straight portions of the pattern are 
typically aligned along the {110} crystal plane. After exposing and 
developing the photoresist, the undeveloped photoresist is stripped to 
expose part of the nitride/oxide film layer. The exposed nitride/oxide 
film is finally etched to form an nitride/oxide film negative image of the 
desired pattern. 
The pathways are formed in the surfaces of the wafers by etching the 
silicon, using either isotropic or anisotropic etch, the choice of which 
is dependent on the shape of the pathway desired. Curved shapes are etched 
using an isotropic etch. Straight shapes may employ either etch, depending 
on the desired cross-sectional shape pathway. If a trapezoidal 
cross-section is desired an anisotropic etch is used. 
If a given wafer is to be etched on both major surfaces using the same 
etch, both sides of the wafer may be masked with resist, the resist 
exposed with the desired pattern on each surface, developed, washed and 
the nitride/oxide etched simultaneously on both surfaces. Then the silicon 
may be simultaneously etched on both surfaces. If different types of 
etchants are to be used on each side of the wafer, all steps for the first 
etch are completed and then the steps are repeated for the second etch. 
After all the etching steps have been completed the vertical passages or 
vias through the wafer are formed by laser cutting through the wafers, 
typically using a pulsed neodymium-YAG laser cutting system. After laser 
cutting, the wafers are again recleaned to remove cutting debris. The 
remaining nitride layer of the negative image is removed from the wafer, 
by using a suitable solvent, such as boiling phosphoric acid, exposing the 
undamaged oxide layer. The remaining oxide layer negative image may 
optionally be removed from the wafer, by using a suitable solvent, such as 
buffered hydrogen fluoride. The wafer is recleaned, using the technique as 
described above. 
Other techniques may be used which are dependent upon the lamina material. 
Laminae which are comprised of group III, IV or V material are processed 
using etching, grinding, drilling and polishing techniques. Laminae 
comprised of glass, Pyrex, or fused silica are fabricated using 
conventional glass cutting, drilling, grinding, and polishing techniques. 
Laminae comprised of ceramic materials may be formed by slip casting, 
consolidated by pressing and fired using well known techniques. 
When all the laminae have been individually processed the laminae are 
carefully stacked in a precisely aligned manner and fusion bonded. To 
achieve good bonding of silicon laminae, the surfaces should be highly 
planar and the oxide layers on each surface should be undamaged. Since 
silicon is somewhat transparent in the infrared, a microscope with an 
infrared video camera may be used, with optional alignment indicia on each 
wafer, to insure precise alignment of the wafers before they are fusion 
bonded. If an outer lamina is comprised of glass, this lamina is then 
anodically bonded to the already fused stack of inner laminae. 
Those skilled in the art, having the benefit of the teachings of the 
present invention as hereinabove set forth, can effect numerous 
modifications thereto. It is readily appreciated that such modifications 
can be made without departing from the spirit of the scope of the present 
invention. Accordingly, such modifications are to be construed as being 
encompassed within the scope of the present invention as set forth in the 
appended claims.