In Re Mouttet ( 2012 )


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  •   United States Court of Appeals
    for the Federal Circuit
    __________________________
    (Serial No. 11/395,232)
    IN RE BLAISE LAURENT MOUTTET
    __________________________
    2011-1451
    __________________________
    Appeal from the United States Patent and Trademark
    Office, Board of Patent Appeals and Interferences.
    ___________________________
    Decided: June 26, 2012
    ___________________________
    BLAISE LAURENT MOUTTET, of Arlington, Virginia, pro
    se.
    RAYMOND T. CHEN, Solicitor, United States Patent
    and Trademark Office, of Alexandria, Virginia, for appel-
    lee. With him on the brief were LYNNE E. PETTIGREW and
    KRISTI L. R. SAWERT, Associate Solicitors.
    __________________________
    Before PROST, O’MALLEY and REYNA, Circuit Judges.
    REYNA, Circuit Judge.
    Mr. Blaise Laurent Mouttet (“Mouttet”) appeals the
    decision of the Board of Patent Appeals and Interferences
    (“Board”) affirming the rejection of all pending patent
    IN RE MOUTTET                                              2
    claims under 
    35 U.S.C. § 103
    (a). Substantial evidence
    supports the Board’s factual determinations, and we
    agree with the Board’s conclusion that Mouttet’s claimed
    invention would have been obvious to one having ordinary
    skill in the art. We therefore affirm.
    I. BACKGROUND
    A. Mouttet’s Patent Application
    On April 3, 2006, sole inventor Mouttet submitted
    utility patent application No. 11/395,232 (“the ’232 appli-
    cation”) entitled “Crossbar Arithmetic Processor.” It
    discloses a computing device for processes such as addi-
    tion, subtraction, multiplication, and division using
    nanoscale materials in a crossbar array. 1 Specifically,
    Mouttet claimed in representative 2 claim 1:
    1. A computing device comprising:
    at least one crossbar array including a first
    set of N conductive parallel wires (N≥2) forming a
    set of columns and a second set of M conductive
    parallel wires (M≥2) forming a set of rows, and
    formed so as to intersect the first set of conductive
    parallel wires, wherein intersections are formed
    between the first and second sets of wires forming
    MxN crosspoints wherein each of the crosspoints
    is programmable so as to be in a relatively high
    conductive state representative of a binary value 1
    1   Nanoscale materials have dimensions ranging be-
    tween 1 and 100 nanometers.
    2  The Board treated Mouttet’s independent claim 1
    as representative according to 
    37 C.F.R. § 41.37
    (c)(1) and
    In re Dance, 
    160 F.3d 1339
    , 1340 n.2 (Fed. Cir. 1998).
    This decision by the Board is uncontested on appeal.
    3                                            IN RE MOUTTET
    or a relatively low conductive state representative
    of a binary value 0;
    a programming unit configured to program
    the crosspoints to have one of the relatively high
    conductive state or the relatively low conductive
    state so that at least one column of the crossbar
    array stores a bit pattern representative of a pro-
    grammed numerical value;
    an input unit configured to provide a bit pat-
    tern representative of an input numerical value to
    the columns of the crossbar array; and
    a post-processing unit configured to convert
    analog signals output from each of the rows of the
    crossbar array into digital output bit patterns and
    configured to combine the digital output bit pat-
    terns so as to form a resultant bit pattern repre-
    sentative of an output numerical value,
    wherein the output numerical value is
    mathematically dependent on both the pro-
    grammed numerical value and the input numeri-
    cal value.
    Ex parte Mouttet, No. 2009-010041, 2011 Pat. App. LEXIS
    15036, at *1-2 (B.P.A.I. Mar. 29, 2011).
    Mouttet’s crossbar array consists of two intersecting
    sets of conductive parallel wires. At the wire junctions, or
    “crosspoints,” a thin film material or molecular compo-
    nent acts as a bridge between the wires. The resistance of
    the thin film material or molecular component between
    the intersecting wires may be altered by controlling the
    voltages applied to individual wires in the first and sec-
    ond sets. By altering the resistance, each crosspoint can
    IN RE MOUTTET                                           4
    be programmed to be in a high resistance (low conduction)
    state or low resistance (high conduction) state. The two
    states can represent the binary values “0” and “1” and
    thus store digital data. For example, Mouttet’s Figure 2b
    from the ’232 application, below, illustrates the internal
    structure of a 3x8 crossbar array with various crosspoints
    in either state after programming:
    Figure 2b depicts binary values 00001001, 00000111, and
    00000011, which in the base 10 number system represent
    the numerals 9, 7, and 3.
    Mouttet’s claimed computing device adds other input
    and output units to the central crossbar array. As shown
    in Figure 1 of the ’232 application, reproduced below, an
    input unit 103 and a program unit 102 provide the neces-
    sary voltage to the array of crossbar wires 101, altering
    the resistance at the crosspoints:
    5                                            IN RE MOUTTET
    By altering the conductive states of the crosspoints, input
    unit 103 and program unit 102 provide the crossbar array
    with bit patterns (a series of “0”s and “1”s) representative
    of numerical values. Post-processing unit 105 converts
    the analog signals from each of the rows of the crossbar
    array 101 into digital output bit patterns representative
    of numerical values, for example, the sum of the values
    provided by the input unit 103 and program unit 102.
    B. Prior Art
    The examiner at the United States Patent and
    Trademark Office (“PTO”) rejected all twenty of Mouttet’s
    pending claims under § 103(a) as unpatentable over a
    publication by Shamik Das 3 (“Das”) and four prior art
    3   Shamik Das, et al., Architectures & Simulations
    for Nanoprocessor Systems Integrated on the Molecular
    Scale, in Introducing Molecular Electronics 479, ch. 17
    (2005), available at http://www.mitre.org/work/tech
    papers/tech papers 05/05 0977/05 0977.pdf.
    IN RE MOUTTET                                              6
    patents: U.S. Patent Nos. 4,633,386 (filed Apr. 6, 1984)
    (“Terepin”), 5,249,144 (filed Sept. 29, 1989) (“Falk”);
    6,693,821 (filed June 28, 2001) (“Hsu”), and 6,867,996
    (filed Aug. 29, 2002) (“Campbell”). The only relevant
    references for purposes of this appeal are Falk, Das, and
    Terepin. See infra nn. 4 & 5.
    1. Falk
    Falk, a patent issued September 28, 1993, discloses a
    programmable computing device for performing arithme-
    tic and logic operations. See Abstract; id. at col.1 ll.7-11.
    Falk’s central circuit component consists of a crossbar
    array having two intersecting sets of parallel optical
    channels, or simply put, crossed paths of light. Id. at col.1
    ll.35-39; col.6 ll.39-42. Figure 1 of Falk illustrates an
    example of a 4x4 optical crossbar circuit:
    FIG. 1
    In Figure 1, the crossbar array has two sets of inputs. Id.
    at col.3 ll.38-51. Input 100 from channel 1 and input 200
    from channel 2 are light sources that have been turned on
    7                                             IN RE MOUTTET
    so as to beam light along optical paths 101 and 201. Id.
    at col.3 ll.38-46. The intensity of light at each intersect-
    ing region along the crossbar’s optical paths (e.g., 300-
    302) represents a particular logic state. Id. at col.1 ll.39-
    42; col.3 ll.46-51. The examiner determined, on the basis
    of these disclosures, that Falk teaches an optical crossbar
    array for its principle arithmetic/logic unit.
    Figure 13 shows the larger computing device that en-
    capsulates the optical crossbar array as arithmetic unit
    133, id. at col.5 ll.48-51 (“arithmetic unit 133 . . . is im-
    plemented as per FIGS. 1-4”):
    FIG. 13
    Falk’s crossbar arithmetic unit 133 receives inputs from
    reordering tables 131 and 132. Id. at col.6 ll.39-48.
    Inputs from 131 and 132 are configured to send signals
    along lines 161-165, providing inputs to crossbar arithme-
    tic unit 133 and programming the device to perform the
    desired arithmetic operation. Id. at col.5 l.67-col.6 l.46;
    IN RE MOUTTET                                              8
    col.6 ll.55-61. Crossbar arithmetic unit 133 produces a
    set of outputs 170 based on the logic states at the crossbar
    intersections. Id. at col.6 ll.46-52. Outputs 170 are
    further processed at unit 134 to represent the result of
    the arithmetic operation at output 180. Id.
    2. Das
    Das, a 2005 publication cited by Mouttet in the ’232
    application, discloses nanoprocessor systems integrated
    on the molecular scale. “By integration on the molecular
    scale,” Das explains generally, “we mean the basic switch-
    ing devices, as well as the wire widths and the pitch
    dimensions (i.e., spacing between the centers of neighbor-
    ing wires), all will measure only a few nanometers—the
    size of a molecule—in the computer systems of interest
    here.” Das at 481.
    Das specifically discloses a nanoscale crossbar array
    with molecular switches. Das’s Figure 17.1 depicts struc-
    tures of one or a few molecules, sandwiched between
    intersecting wires at the junctions of a crossbar array:
    “Fig. 17.1 ‘Crossbar’ array of nanowires with molecular
    devices at junctions.”
    9                                            IN RE MOUTTET
    Das at 483. Das explains that the electrical behavior of
    the molecular-scale structures at each junction can act as
    a switch with two states: a high-conductance “on” state
    and a low-conductance “off” state. Id.; see also id. at 484
    & fig.17.2. This “allows the ‘programming’ of a junction
    into one of two states. Such bistable switches are essen-
    tial components of any computing system.” Id. at 483.
    On the basis of these disclosures, the examiner deter-
    mined that Das teaches molecular switches on a nano-
    scale crossbar array capable of being programmed into
    high resistance or low resistance states, thereby con-
    structing functional circuits that can be used to build
    larger processor systems. Id.
    3. Terepin
    Terepin, a patent issued December 30, 1986, is enti-
    tled “Digital Signal Processor.” The examiner determined
    that Terepin teaches the use of analog-to-digital (“A/D”)
    converter capable of converting analog signals to digital
    bit patterns. Terepin, col.3 ll.22-27.
    C. Examiner Rejection and Board Decision
    The examiner found that Falk taught all of Mouttet’s
    recited limitations in representative claim 1 except for (1)
    a crossbar array implemented with electrical wires rather
    than optical light paths, (2) crosspoints with programma-
    ble states based on electrical conductivity rather than
    optical intensity, and (3) conversion of analog signal
    outputs to digital output bit patterns in the post-
    processing unit. Ex parte Mouttet, 2011 Pat. App. LEXIS
    15036, at *3-4. The examiner relied on Das to teach the
    missing crossbar array using wires and crosspoints that
    are programmable to have electrical conductive states,
    and on Terepin to teach a component converting analog
    IN RE MOUTTET                                               10
    signals to digital bit patterns. The examiner thus rejected
    claims 1, 2, 6-12, and 16-20 of the ’232 application under
    
    35 U.S.C. § 103
    (a) as obvious over Falk, in view of Das
    and Terepin. 4 Mouttet appealed to the Board under 
    35 U.S.C. § 134
    (a).
    On March 29, 2011, the Board affirmed the exam-
    iner’s rejection of all twenty claims. 5 Ex parte Mouttet,
    2011 Pat App. LEXIS 15036, at *1. The Board agreed
    that an ordinarily skilled artisan, i.e., an electrical engi-
    neer with several years of related industry experience,
    would have recognized that substituting Das’s wired
    crossbar array for Falk’s optical path crossbar would have
    predictably yielded Mouttet’s claimed computing device.
    
    Id. at *6
    , *9 (citing KSR Int’l Co. v. Teleflex, Inc., 
    550 U.S. 398
    , 416 (2007)). The Board found that while Falk notes
    certain advantages to optical devices, the reference in no
    way suggests that using electronic hardware instead of
    optical hardware would destroy Falk’s operability as a
    programmable arithmetic unit, nor that it teaches away
    from electrical circuitry. Id. at *7. The Board also found
    adequate reasons to combine the references because (1) as
    taught in Das, electrical circuitry “enable[s] more complex
    and specialized functions to be performed,” (2) “combining
    these references would predictably yield the claimed
    computing device,” and (3) “the relative advantages and
    4   The examiner also rejected claims 3, 4, 13, and 14
    under § 103(a) as unpatentable over Falk, Das, Terepin,
    and Hsu, as well as rejecting claims 5 and 15 under
    § 103(a) as unpatentable over Falk, Das, Terepin, and
    Campbell.
    5   As the rejections of claims 3-5 and 13-15 were not
    appealed to the Board by pointing out with particularity
    alleged errors in the examiner’s reasoning, the Board
    sustained these rejections as well without discussing the
    teachings of Hsu and Campbell. These issues are not
    before us in this appeal.
    11                                           IN RE MOUTTET
    disadvantages in selecting electrical circuitry in lieu of
    optical circuitry amounts to an engineering tradeoff—a
    decision well within the level of ordinarily skilled arti-
    sans.” Id. at *8-9. Importantly, the Board noted that
    there is no requirement that the examiner show how to
    physically incorporate Das’s features into Falk, because
    obviousness focuses on what the combined teachings
    would have suggested. Id. at *8 (citing In re Keller, 
    642 F.2d 413
    , 425 (CCPA 1981)). The Board affirmed the
    examiner rejection of all claims in Mouttet’s application
    on § 103(a) grounds. Id. at *9-10. Mouttet appealed to
    this court, submitting an Overdue Informal Brief of
    Appellant on August 5, 2011. 6 We exercise jurisdiction
    pursuant to 
    28 U.S.C. § 1295
    (a)(4)(A).
    II. DISCUSSION
    A. Standard of Review
    Whether an invention would have been obvious to one
    of ordinary skill in the art is a legal determination based
    on underlying findings of fact. KSR, 
    550 U.S. at 427
    ; In
    re Gartside, 
    203 F.3d 1305
    , 1316, 319 (Fed. Cir. 2000)
    (citing Graham v. John Deere Co., 
    383 U.S. 1
    , 17-18
    (1966)). The scope and content of the prior art, as well as
    whether the prior art teaches away from the claimed
    invention, are determinations of fact. See Para-Ordnance
    Mfg., Inc. v. SGS Importers Int’l, Inc., 
    73 F.3d 1085
    , 1088
    (Fed. Cir. 1995). The PTO bears the initial burden of
    showing a prima facie case of obviousness. In re Mayne,
    
    104 F.3d 1339
    , 1341 (Fed. Cir. 1997). If the PTO carries
    its burden, the applicant must rebut the PTO’s showing.
    
    Id.
    6In re Mouttet, No. 2011-1451, 
    2011 U.S. App. LEXIS 17401
     (Fed. Cir. Aug. 19, 2011).
    IN RE MOUTTET                                           12
    While this court reviews the Board’s legal conclusion
    of obviousness without deference, it upholds the Board’s
    factual findings if supported by substantial evidence. In
    re Gartside, 
    203 F.3d at 1313-16
    . Substantial evidence is
    something less than the weight of the evidence but more
    than a mere scintilla of evidence. 
    Id.
     at 1312 (citing
    Consol. Edison Co. v. Nat’l Labor Relations Bd., 
    305 U.S. 197
    , 229-30 (1938)). It means such relevant evidence as a
    reasonable mind might accept as adequate to support a
    conclusion. Consol. Edison, 
    305 U.S. at 229-30
    . Thus,
    “where two different, inconsistent conclusions may rea-
    sonably be drawn from the evidence in record, an agency’s
    decision to favor one conclusion over the other is the
    epitome of a decision that must be sustained upon review
    for substantial evidence.” In re Jolley, 
    308 F.3d 1317
    ,
    1329 (Fed. Cir. 2002); see also Gartside, 
    203 F.3d at 1312
    (noting that the possibility of drawing inconsistent con-
    clusions from the evidence does not prevent the Board’s
    findings from being supported by substantial evidence).
    B. Analysis
    A claimed invention is unpatentable “if the differences
    between the subject matter sought to be patented and the
    prior art are such that the subject matter as a whole
    would have been obvious at the time the invention was
    made to a person having ordinary skill in the art to which
    said subject matter pertains.” 
    35 U.S.C. § 103
    (a). Where
    “a patent claims a structure already known in the prior
    art that is altered by the mere substitution of one element
    for another known in the field, the combination must do
    more than yield a predictable result.” See KSR, 
    550 U.S. at 416
    . A reference may be read for all that it teaches,
    including uses beyond its primary purpose. See 
    id. at 418-21
    ; see also Beckman Instruments, Inc. v. LKB Pro-
    dukter AB, 
    892 F.2d 1547
    , 1551 (Fed. Cir. 1989).
    13                                           IN RE MOUTTET
    The government argues on appeal that substantial
    evidence supports the factual determinations underlying
    the Board’s conclusion that Mouttet’s claimed invention
    would have been obvious in view of the combination of
    Falk, Das, and Terepin. The ’232 application broadly
    claims a computing device comprising a crossbar array of
    wires with programmable crosspoints that can be in a
    relatively high or relatively low conductive state, pro-
    gramming and input units, and a post-processing unit
    that converts analog signals to digital signals to output a
    numerical value. The Board found that Falk discloses a
    computing device with all the recited limitations of Mout-
    tet’s representative claim 1 except that Falk lacks an A/D
    converter and uses optical paths rather than electrical
    wires for the crossbar array. The Board found that Tere-
    pin supplied the missing A/D converter and that Das
    taught the electrical crossbar array with programmable
    crosspoints in relatively high or low conductive states.
    The government maintains that a person having ordinary
    skill in the art would have implemented Falk’s arithmetic
    processor design using Das’s known electrical crossbar
    array.
    Mouttet makes two arguments on appeal: first, that
    substituting electronic hardware for optical hardware
    would destroy the Falk device’s principle of operation and
    physical structure; and second, that Falk teaches away
    from the claimed invention. Each is addressed below.
    1. Principle of Operation and Physical Structure
    According to Mouttet, the Board erred in finding that
    Falk does not suggest that using electronic wires instead
    of optical paths would destroy Falk’s ability to operate as
    a programmable arithmetic unit. Mouttet argues that
    eliminating the optical components from Falk impermis-
    IN RE MOUTTET                                           14
    sibly destroys its principle of operation. He cites In re
    Ratti, 
    270 F.2d 810
    , 813 (CCPA 1959), for the proposition
    that if the combination of references would change the
    principle of operation of the prior art, then the teachings
    cannot suffice to render claims obvious.
    We find the Board’s determination that eliminating
    the optical components of Falk would not destroy its
    principle of operation to be supported by substantial
    evidence. As the examiner found, the type of circuitry
    used is the main difference between Mouttet’s invention,
    which is based on electrical conductivity, and Falk’s
    invention, which is based on optical paths. But this
    difference does not affect the operability of Mouttet’s
    broadly claimed device—a programmable arithmetic
    processor. The Board found, and we agree, that the
    principle of operation of Falk’s computing device is its
    high level ability to receive inputs into a programmable
    crossbar array and processing the output to obtain an
    arithmetic result. Similarly, Mouttet’s claim 1 operates
    by combining Falk, Das, and Terepin to receive inputs
    into a programmable crossbar array and processing the
    output to obtain an arithmetic result. Stated differently,
    the examiner saw nothing in the programming and proc-
    essing of junction states in Falk that is unique to its
    optical implementation, and Mouttet has not shown
    otherwise. Thus, the Board’s determination that the
    difference in the circuitry—electrical versus optical—does
    not affect the overall principle of operation of a program-
    mable arithmetic processor was supported by substantial
    evidence. See, e.g., In re Umbarger, 
    407 F.2d 425
    , 430-31
    (CCPA 1969) (finding Ratti inapplicable where the modi-
    fied apparatus will operate “on the same principles as
    before”).
    15                                            IN RE MOUTTET
    Mouttet further objects that replacing Falk’s optical
    crossbar circuitry with Das’s electrical crossbar circuitry
    would destroy the physical structure of Falk. Mouttet
    argues that there is no evidence that electrical crossbar
    circuitry would have been recognized by ordinarily skilled
    artisans as equivalent to, or able to be substituted for,
    optical crossbar circuitry.
    Any alleged nonequivalence in the type of circuit is ir-
    relevant to the Board’s determination since the examiner
    did not rely on art-recognized equivalence in substituting
    the crossbar arrays. It is well-established that a determi-
    nation of obviousness based on teachings from multiple
    references does not require an actual, physical substitu-
    tion of elements. In re Etter, 
    756 F.2d 852
    , 859 (Fed. Cir.
    1985) (en banc) (“Etter’s assertions that Azure cannot be
    incorporated in Ambrosio are basically irrelevant, the
    criterion being not whether the references could be physi-
    cally combined but whether the claimed inventions are
    rendered obvious by the teachings of the prior art as a
    whole.”); In re Sneed, 
    710 F.2d 1544
    , 1550 (Fed. Cir. 1983)
    (“[I]t is not necessary that the inventions of the references
    be physically combinable to render obvious the invention
    under review.”); In re Keller, 
    642 F.2d 413
    , 425 (CCPA
    1981) (“The test for obviousness is not whether the fea-
    tures of a secondary reference may be bodily incorporated
    into the structure of the primary reference . . . .”).
    Thus, it was not requisite to the Board’s § 103(a) de-
    termination that Das’s features be deemed equivalent for
    purposes of substitution into Falk’s device. Rather, the
    test for obviousness is what the combined teachings of the
    references would have suggested to those having ordinary
    skill in the art. Id. The Board properly found that an
    electrical engineer with several years of related industry
    experience would indeed have recognized that Falk’s
    IN RE MOUTTET                                             16
    arithmetic processor could have been combined with Das’s
    wired crossbar array to predictably yield Mouttet’s
    claimed computing device. See KSR, 
    550 U.S. at 416, 421
    .
    We further note that Mouttet’s objection to substitut-
    ing the electrical components of Das into the optical
    crossbar array of Falk is based on an incorrect assump-
    tion: that, because the Board designated Falk as the “base
    reference,” Falk’s optically-based crossbar implementa-
    tion—vis-à-vis Das’s electrically-based implementation—
    is a controlling principle of operation that any prior art
    combination must preserve. But where the relevant
    factual inquiries underlying an obviousness determina-
    tion are otherwise clear, characterization by the examiner
    of prior art as “primary” and “secondary” is merely a
    matter of presentation with no legal significance. See In
    re Bush, 
    296 F.2d 491
    , 496 (CCPA 1961) (Rich, J.); In re
    Krammes, 
    314 F.2d 813
    , 816-17 (CCPA 1963). While we
    recognize that there may be some cases in which relevant
    factual determinations inhere in such characterization of
    prior art references, this case is not one.
    Here, as found by the Board, Das clearly teaches what
    is at the core of Mouttet’s invention: a crossbar of parallel
    conductive wires with programmable molecular-scale
    switches at the junctions. Das at 483-84. Using Das’s
    principles of operation, one skilled in the art readily could
    have made a larger computer processor system using
    known input, output, and A/D converter units, as taught
    in Falk and Terepin. Thus, from either perspective, the
    claimed invention would have been obvious under
    § 103(a).
    17                                             IN RE MOUTTET
    2. Falk Does Not “Teach Away” from Electrical
    Circuitry
    Mouttet argues that Falk “teaches away” from the
    claimed invention. A reference that properly teaches
    away can preclude a determination that the reference
    renders a claim obvious. See DePuy Spine, Inc. v. Med-
    tronic Sofamor Danek, Inc., 
    567 F.3d 1314
    , 1326-27 (Fed.
    Cir. 2009). Whether or not a reference teaches away from
    a claimed invention is a question of fact. See In re Napier,
    
    55 F.3d 610
    , 613 (Fed. Cir. 1995).
    To this end, Mouttet relies on the following passage to
    suggest that Falk teaches away from electrical circuitry:
    There is a fundamental difference between optical
    circuits, in which the information carriers are
    photons, and electronic circuits, where the carri-
    ers are electrons . . . . [I]n optical devices, there
    exist interconnect possibilities that do not exist
    with electronic hardware, in particular, intercon-
    nected parallel architectures which permit digital
    arithmetic and logic operations to be performed in
    a completely parallel, single step process. After
    the inputs are switched on, the output appears in
    the time it takes a photon to transit the device.
    No faster computation time is possible.
    Falk, col.1 ll.12-17.
    In In re Gurley, 
    27 F.3d 551
    , 553 (Fed. Cir. 1994), we
    emphasized that “[a] reference may be said to teach away
    when a person of ordinary skill, upon reading the refer-
    ence, would be discouraged from following the path set
    out in the reference, or would be led in a direction diver-
    gent from the path that was taken by the applicant.”
    IN RE MOUTTET                                             18
    Thus, the “mere disclosure of alternative designs does not
    teach away.” In re Fulton, 
    391 F.3d 1195
    , 1201 (Fed. Cir.
    2004). This court has further explained that just because
    better alternatives exist in the prior art does not mean
    that an inferior combination is inapt for obviousness
    purposes. Gurley, 
    27 F.3d at 553
    .
    The Board determined that the Falk passage Mouttet
    recites does not “teach away” from a computing device
    using an electrical crossbar array under our law. That
    determination is supported by substantial evidence. Falk
    indeed recognizes a “fundamental difference” between
    circuit types, and even suggests that electrical circuits are
    an inferior to optical circuitry for certain purposes. Falk,
    col.1 ll.12-17. But the Board found that “even if Falk’s
    [sic] discusses a preferred embodiment (e.g., an optical
    circuit with more interconnect possibilities), this does not
    teach away from a non-preferred embodiment containing
    an arithmetic/logic system having electrical circuitry with
    wire sets.” March 29, 2011 Board Decision at 6. While
    Mouttet’s reading of Falk is plausible, our standard of
    review mandates that we uphold factual findings that are
    supported by substantial evidence as opposed to revisiting
    them de novo.
    As noted by the Board, Mouttet fails to cite any refer-
    ence suggesting that the claimed invention would be
    unlikely to work using electrical circuitry; he alleges only
    that it may be inferior for certain purposes. See id.;
    Gurley, 
    27 F.3d at 553
    ; Baxter Int’l, Inc. v. McGaw, Inc.,
    
    149 F.3d 1321
    , 1328 (Fed. Cir. 1998) (finding no teaching
    away where nothing in the prior art device suggested that
    the claimed invention was unlikely to work). In this case,
    a known system such as an arithmetic/logic unit “does not
    become patentable simply because it has been described
    as somewhat inferior to some other product for the same
    19                                           IN RE MOUTTET
    use,” such as an arithmetic/logic unit having electrical
    circuitry despite fewer interconnect possibilities than
    optical circuitry. Gurley, 
    27 F.3d at 553
    . Nor do we
    recognize in Falk any teaching—sufficient to overturn the
    contrary determination of the Board—that a crossbar
    arithmetic processor “should not” or “cannot” be imple-
    mented with electrical circuitry, Para-Ordnance, 73 F.3d
    at 1090, or that “criticize[s], discredit[s], or otherwise
    discourage[s]” a device like Mouttet’s, In re Fulton, 
    391 F.3d at 1201
    .
    III. CONCLUSION
    We find that the Board’s factual determinations are
    supported by substantial evidence, and that it would have
    been obvious to persons having ordinary skill in the art to
    combine the features of Falk, Das, and Terepin to arrive
    at the invention claimed in the ’232 application. The
    Board’s decision is therefore affirmed.
    AFFIRMED
    COSTS
    No costs.