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`C h e m i s t r y a n d H i s t o r y
`
`The Story of Nitinol:
`The Serendipitous
`Discovery of the
`Memory Metal and
`Its Applications
`
`GEORGE B. KAUFFMAN*
`California State University, Fresno
`Fresno, CA 93740-0070
`
`ISAAC MAYO
`College of Veterinary Medicine
`Cornell University
`Ithaca, NY 14853-6401
`
`Science and
`technology
`abound with
`examples of
`serendipity….
`
`T
`
`he shape-retaining alloy Nitinol (Nickel Titanium
`Naval Ordance Laboratory), the “metal with a
`memory,”
`is
`revolutionizing manufacturing,
`engineering, and medicine as countless products that
`“think” for themselves enter the marketplace. This article
`recounts its discovery in 1959 by William J. Buehler of the
`U.S. Naval Ordnance Laboratory, its subsequent development
`by Buehler and Frederick E. Wang, and its applications in
`orthopedic and cardiovascular surger, orthodontics, solid-state
`heat engines, “shrink-to-fit” pipe couplers for aircraft, safety
`products, eyeglass frames, and toys. The serendipitous nature
`of the discovery, the solid-to-solid (austenite to martensite)
`
`COOK
`Exhibit 1019-0001
`
`

`

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`phase transition that produces the alloy’s unusual properties, its numerous practical
`applications, and the ready availability of samples make the alloy an ideal, exciting,
`and thought-provoking topic for chemistry courses at all levels in both lecture and
`laboratory.
`
`What do these technological advances have in common—fire, cooking, agriculture, the
`wheel, and weapons? All were probably encountered by chance rather than as the
`result of a planned search and discovery. In Mark Twain’s words, “Name the greatest
`of inventors. Accident.”
`
`These cases are examples of serendipity—the accidental happening became a
`discovery only when the inventor realized its significance. The best historical example
`of serendipity is probably Christopher Columbus’ discovery of America while seeking
`a sea route to the East Indies. The word itself was coined and first used in 1754 by
`Horace Walpole, 4th Earl of Orford. Walpole insisted that the serendipitous discovery
`be not only accidental but also be arrived at in the course of seeking something
`else [1].
`
`Science and technology abound with examples of serendipity: Pasteur’s discovery of
`optical asymmetry, Fleming’s discovery of penicillin, and the discovery of a unique
`property of the nickel–titanium alloy Nitinol, which can “memorize” a predetermined
`shape and return to this shape under certain temperature conditions.
`
`Nitinol’s Beginnings
`In January 1958 William J. Buehler (Figure 1), a metallurgist at the Naval Ordnance
`Laboratory (NOL) had completed research on a series of iron–aluminum alloys [2].
`Buehler, born in Detroit, Michigan on October 25, 1923, had received his Bachelor of
`Science degree in chemical engineering (1944) and his Master of Science degree in
`metallurgical engineering (1948) from Michigan State University at East Lansing. In
`1948 he was hired as an Instructor in Metallurgy at North Carolina State University in
`Raleigh. In June 1951 NOL in White Oak, Maryland was looking for a mechanical
`engineer for their staff, and Buehler was hired. He was promoted to Metallurgist in
`January 1952 and by July 1956 was a Supervisory Physical Metallurgist [3].
`
`COOK
`Exhibit 1019-0002
`
`

`

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`FIGURE 1. WILLIAM J. BUEHLER IN 1968, PICTURED WITH A DEMONSTRATION OF NITINOL WIRE. ELECTRICITY
`WAS PASSED THROUGH A STRAIGHT PIECE OF WIRE, AND THE WIRE WOULD CHANGE INTO THE WORD
`“INNOVATIONS.” THE OAK LEAF, U.S. NAVAL ORDNANCE LABORATORY, WHITE OAK, MARYLAND, JUNE 1968.
`
`The “between-projects boredom” began to set in for Buehler after completing the iron–
`aluminum alloy project [2]:
`
`It was at this point… that lady luck played a key role. I found within the U.S.
`Naval Ordnance Laboratory an ongoing materials project which had the goal of
`developing metallic materials for the nose cone of the U.S. Navy Polaris
`reentry vehicle…. The in-house project was under the direction of Mr. Jerry
`Persh, an aerodynamicist. I was able to attach myself to this project, and my
`initial task was to provide physical and mechanical property data on existing
`metals and alloys for computer-assisted boundary layer calculations. These
`calculations were to simulate the heating, etc. of a reentry body through the
`earth’s atmosphere. My informational role in this project very quickly became
`somewhat boring, and I almost immediately began to think in terms of possibly
`tailoring newly developed alloys that might better satisfy the drastic thermal
`requirements of the reentry body. My initial thought was to look more closely at
`intermetallic compound alloys, where the two component metals form a
`metallic phase that has simple stoichiometric proportions and generally
`possesses a high melting temperature—major limitation, DUCTILITY.
`
`Events in Buehler’s personal life at this same time exacerbated his ennui [4]:
`
`COOK
`Exhibit 1019-0003
`
`

`

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`My first wife and I separated, and I spent a tremendous amount of time
`working in the laboratory… you might say it’s a good feature that came out of a
`disastrous situation. I had lots of time at that point… in the state of Maryland
`the law required a three-year waiting period of separation before formal
`divorce could be handled. During that three-year period I literally worked day
`and night. Many days I would get up at 4 o’clock in the morning, go to the lab,
`and not go home until 11 o’clock at night. Between working at the laboratory
`and playing golf, I really didn’t do anything other than eat or sleep.
`
`To initiate the reentry material project Buehler consulted Max Hansen’s recently
`published Constitution of Binary Alloys [5]. This book contained what was then the
`most complete collection of binary constitution diagrams, showing the solid-state
`phase relationships of two–component metallic alloys as a function of composition and
`temperature. Buehler selected approximately sixty intermetallic compound alloys for
`further study [6]. This number was then reduced, for various logical reasons, to twelve
`alloy systems. One of the systems, an equiatomic nickel–titanium alloy, immediately
`exhibited considerably more impact resistance and ductility than the other eleven
`alloys [7]. In 1953 Dr. Harold Margolin of New York University and his associates
`had carried out some studies on phase changes of nickel–titanium alloys but had
`sensed no uniqueness among them [8].
`
`In 1959 Buehler decided to concentrate on the equiatomic nickel–titanium composition
`alloys and relegated the intermetallic compound systems to secondary status. He
`named his discovery NITINOL (Nickel Titanium Naval Ordnance Laboratory) [7].
`That same year he made an observation about his discovery that hinted at the
`extraordinary, but still undiscovered, property of Nitinol [2].
`
`I distinctly remember my very exciting discovery of the acoustic damping
`change with temperature change near room temperature. This unusual event
`unfolded when my…assistant… and I were melting a number of [Nitinol] bars
`in the arc-melting furnace. On the day in question (circa 1959), six arc-cast
`bars were made. While cooling on the transite-topped table, the first bars arc-
`cast into bar form had cooled to near room temperature, while the last bars to
`be cast were still too hot… to be handled with bare hands. Between the cool
`(first bar) and the very warm bar (last bar) were four arc-cast bars possessing
`a broad spectrum of temperatures…. My “hands-on” approach caused me to
`take the cooler bar(s) to the shop grinder to manually grind away any surface
`irregularities that might produce a subsequent scaly or bad… surface. In going
`from the table to the bench grinder, I purposely dropped the cool (near room
`temperature) bar on the concrete laboratory floor [a quick test to determine
`roughly the damping capacity of an alloy]. It produced a very dull “thud,” very
`
`COOK
`Exhibit 1019-0004
`
`

`

`5 / V O L . 2 , N O . 2
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`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
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`much like what one would expect from a similar size and shape lead bar. My
`immediate concern was that the arc-casting process may have in some way
`produced a multitude of micro cracks within the bar—thus producing the
`unexpected damping phenomena. With
`this possibly discouraging
`development in mind, I decided to drop the others on the concrete floor. To my
`amazement, the warmer bars rang with bell-like quality. Following this I literally
`ran with one of the warmer bars (that rang) to the closest source of cold
`water—the drinking fountain—and chilled the warm bar. After thorough cooling
`the bar was again dropped on the floor. To my continued amazement it now
`exhibited the leaden-like acoustic response. To confirm this unique change,
`the cooled bars were heated through in boiling water—they now rang brilliantly
`when dropped upon the concrete floor. Subsequent discussions with my
`melter assistant revealed that he had in no way mixed or altered the alloy
`compositions during repeated melting. This immediately alerted me to the fact
`that the marked acoustic damping change was related to a major atomic
`structural change, related only to minor temperature variation.
`
`Following the startling acoustic damping discovery, other seemingly related
`unique changes were observed. More interestingly, these changes also
`occurred in about the same temperature range as the acoustic damping
`change. Examples of some of these correlatable phenomena were:
`• Polished plane metallographic alloy surface when heated slightly (100 (cid:176) C to
`200 (cid:176) C; 212 (cid:176) F to 392 (cid:176) F) exhibited an obvious eruption or recontouring of
`the surface. Plate-like surface shearing occurred and appeared to form
`along certain crystallographic planes.
`• Microhardness indentations made at room temperature remained stable in
`size at room temperature. However, when heated slightly (100 (cid:176) C to
`200 (cid:176) C; 212 (cid:176) F to 392 (cid:176) F), they tended to significantly reduce in size.
`• Metallography specimens polished using standard Al2O3 abrasive followed
`by etching always revealed a typical acicular martensitic structure that one
`would typically find in quench-hardened steel. It was only after very careful
`diamond polishing (with minimal surface strain) that the true NITINOL base
`structure was revealed.
`• Acoustic damping, strain, and microstructure combined with minor
`temperature variation were all, in their way, trying to tell me that this was an
`overtly dimensionally mobile alloy capable of major atomic movement in a
`rather low temperature regime—near room temperature. With all of the
`signals above what major act did NITINOL finally have to perform to reveal
`its incredibly unique shape-memory property?
`
`COOK
`Exhibit 1019-0005
`
`

`

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`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
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`Strain and Heat-actuated Recovery—A Serendipitous Discovery
`In the early 1960s Buehler prepared a long, thin (0.010-inch thick) strip of Nitinol to
`use in demonstrations of the material’s unique fatigue-resistant properties. He bent the
`strip into short folds longitudinally, forming a sort of metallic accordion. The strip was
`then compressed and stretched (as an accordion) repeatedly and rapidly at room
`temperature without breaking. In 1961 a laboratory management meeting was
`scheduled to review ongoing projects. Unable to attend, Buehler sent the late Raymond
`C. Wiley, his newly acquired professional metallurgical assistant, to the meeting to
`present Buehler’s work. As one of their “props” for the review, Wiley took the
`accordion folded fatigue-resistant strip. During the presentation, it was passed around
`the conference table and flexed repeatedly by all present. One of the Associate
`Technical Directors, Dr. David S. Muzzey, who was a pipe smoker, applied heat from
`his pipe lighter to the compressed strip. To everyone’s amazement, the Nitinol
`stretched out longitudinally [7]. The mechanical memory discovery, while not made in
`Buehler’s metallurgical laboratory, was the missing piece of the puzzle of the earlier-
`mentioned acoustic damping and other unique changes during temperature variation.
`This serendipitous discovery became the ultimate payoff for Nitinol [7].
`
`In 1962 Dr. Frederick E. Wang (Figure 2) joined Buehler’s group at the Naval
`Ordnance Laboratory, his expertise in crystal physics being vitally needed. Wang, born
`on August 1, 1932 in Su-Tou, Formosa (now Taiwan), emigrated to the United States
`and did his undergraduate work in chemistry and physics at the University of
`Tennessee at Knoxville. After receiving his doctorate in physical chemistry from
`Syracuse University in 1960 [9, 10], he worked as a postdoctoral associate for future
`(1976) Nobel chemistry laureate William Nunn Lipscomb, Jr. at Harvard University,
`until he left to join Buehler at NOL. The commercial applications of Nitinol that were
`to come would not have been possible without Wang’s discovery of how the shape-
`memory property of Nitinol works [11].
`
`An alloy such as Nitinol with a mechanical memory requires certain basic atomic
`structural characteristics. The first requisite is an atomically ordered solid-state parent
`phase, classically called austenite (named for the English metallurgist Sir William
`Chandler Roberts-Austen, 1843–1902) that exists in the higher temperature regime.
`Secondly, at a lower temperature, the atoms of the ordered austenite phase must be
`capable of solid-to-solid “shearing” into a very complex, new atomic arrangement or
`phase, which has been given the name martensite (named for the German
`
`COOK
`Exhibit 1019-0006
`
`

`

`7 / V O L . 2 , N O . 2
`T H E C H E M I C A L E D U C A T O R
`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
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`FIGURE 2. DR. FREDERICK E. WANG.
`
`martensite
`austenite
`1850–1914). The
`metallographer, Adolf Martens,
`transformation (transition) proceeds through a critical temperature range or in special
`situations with applied stress and strain (stress-induced martensite). Thus Nitinol is
`said to undergo a martensite transformation. The complex relative movement of atoms
`within the martensite phase is far too complicated to be described in detail here. For
`the sake of simplicity, one can think of the solid Nitinol alloy in terms of a decreasing
`temperature profile. Starting below the alloy melting point and down to 600–700 (cid:176)C
`(1112–1292 (cid:176) F) the crystal structure is disordered body-centered cubic. From 600 (cid:176)C
`(1112 (cid:176)F) to the austenite
`martensite transformation temperature range (TTR), the
`crystal structure becomes that of an “ordered” cubic, frequently called a CsCl,
`structure. As the alloy cools through the transformation temperature range (TTR), its
`atoms “shear,” forming the new, rather complex martensite phase. The critical features
`to be emphasized here are the austenite
`martensite transformation (transition) and
`the temperature or temperature range (TTR) where this solid-state shear mechanism
`occurs [12] (Figure 3). In the Nitinol–type alloys this TTR can be varied over a
`realistic temperature range from 100 (cid:176)C to well below liquid nitrogen temperature
`(bp –195.8 (cid:176) C or –320 (cid:176) F) by varying the nickel–titanium ratio or ternary alloying with
`small amounts of other metallic elements, e.g., Co, Fe, V, etc.
`
`COOK
`Exhibit 1019-0007
`
`

`

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`T H E C H E M I C A L E D U C A T O R
`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
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`FIGURE 3. A MULTICRYSTALLINE METAL SAMPLE. EACH PATTERN REPRESENTS A DIFFERENT GRAIN OF
`RANDOM SHAPE, SIZE, AND ORIENTATION OF THE ATOM LATTICE. BLACK INDICATES GAPS BETWEEN GRAINS.
`THE BLOW-UP ON THE RIGHT SHOWS THE STRUCTURE OF THE AUSTENITE PHASE OF THE NITINOL ATOMIC
`LATTICE CALLED "BODY-CENTERED CUBIC:” THE CUBES ARE INTERTWINED SUCH THAT EACH CORNER IS IN
`THE CENTER OF ANOTHER CUBE. THE DISTANCE TO THE CENTER OF A CUBE FROM A CORNER IS SHORTER
`THAN THE DISTANCE TO A NEIGHBORING CORNER. THUS THE “NEAREST NEIGHBORS” OF EACH NICKEL ATOM
`(SHOWN BY THE WHITE BALLS) ARE TITANIUM ATOMS (BLACK BALLS), NOT OTHER NICKEL ATOMS; AND VICE-
`VERSA [13].
`
`Nitinol is a conglomeration of tiny regions of single crystals, called grains, all of
`random size, shape, and orientation. To fix a desired shape in Nitinol, it must be heated
`to approximately 500 (cid:176)C (932 (cid:176)F) while being constrained in its desired fixed position.
`The effect of the heating is the restructuring of the atomic lattice within the individual
`grains, and the atoms of the grains adopt the austenite (atomically ordered) phase,
`which has an atomic structure in which each nickel atom is surrounded by eight
`titanium atoms at the corners of the cube. Each titanium atom is likewise surrounded
`by a cube of nickel atoms. Figure 3 shows a sketch of this arrangement [13].
`
`COOK
`Exhibit 1019-0008
`
`

`

`9 / V O L . 2 , N O . 2
`T H E C H E M I C A L E D U C A T O R
`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
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`For example, when a Nitinol wire cools below its transition temperature range (TTR),
`the austenite phase inside the grains changes to the martensite phase, which means that
`the nickel and titanium atoms within the wire assume a different and more complex
`three-dimensional arrangement. The austenite structure is slightly distorted, but these
`accommodating distortions are on the atomic scale and thus are not visible. There
`are 24 three-dimensional variants of this slight, atomic-scale distortion [13]. Thus the
`Nitinol wire can be cooled from the austenite temperature range, through the TTR, to
`room temperature without changing its shape, even though austenite-to-martensite
`phase transformations occur. If the cooled wire (at a temperature lower than its TTR) is
`put under strain by stretching, some of the martensite undergoes atomic shear that is
`caused by the strain. Greater strain leads to more transformation [14]. In Nitinol an
`overall strain approaching 8% can be attributed to martensite shear. Strains in excess
`of about 8% are not the result of martensite shear and are therefore not recoverable.
`
`When distorted Nitinol alloy is warmed, the motion of the atoms is again increased. To
`accommodate the increased thermal motion the atoms slip back into the austenite
`phase configuration, which also restores the original shape of the alloy. In nonmemory
`metals, the strain of a deformation must be absorbed by the rearrangement of entire
`grains because the atoms within the grains are locked rigidly into their lattice
`positions. It is impossible to get the grains back into exactly the same positions after
`such a deformation. In Nitinol, however, the grains stay in place—instead, the atoms
`move [13]. If the recovery of shape is restrained when heating above the TTR
`(austenite phase), a force will be available for doing work or gripping another
`object [15].
`
`No discussion of Nitinol, the preeminent shape–memory alloy, would be complete
`without a brief mention of other alloy systems that have exhibited the shape-memory
`property in at least some limited form. The most significant examples are copper–zinc
`(brass), copper–zinc–aluminum, and gold–cadmium alloys [15]. Also, to a lesser and
`varying degree, shape memory is found in such diverse alloy systems as iron–platinum,
`indium–cadmium, iron–nickel, nickel–aluminum, and stainless steel [15]. What limits
`the shape-memory applications potential of these other alloy systems? Basically, none
`possess the combined property advantages of Nitinol. The list of a few key Nitinol
`advantages would include overall physical and mechanical properties, magnitude of
`strain-heat recovery, energy conversion, general corrosion resistance, human tissue
`and body fluid compatibility for medical applications, ease in reliably altering the
`
`COOK
`Exhibit 1019-0009
`
`

`

`1 0 / V O L . 2 , N O . 2
`T H E C H E M I C A L E D U C A T O R
`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
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`memory-recovery temperature through alloying variations, and a reasonable fabricated
`alloy cost.
`
`Early Research and Uses of Nitinol
`Progress in getting Nitinol into consumer applications came slowly because of early
`problems with its manufacture and because of its expense [16]. A major problem was
`inconsistency among batches of Nitinol. Supposedly identical batches did not possess
`the same transition temperature. These inconsistencies were not a problem for
`laboratory demonstrations, but they hindered the manufacture of viable engineering
`materials [17]. Buehler and Wang’s research group at NOL continued to work on and
`refine the Nitinol manufacturing process until the bugs and glitches were eliminated
`[18, 19]. In April 1967 Wang organized and chaired a symposium on Nitinol and
`associated compounds. Thirteen papers were presented at the meeting [20].
`
`The first successful Nitinol product was the Raychem Corporation’s Cryofit™ “shrink-
`to-fit” pipe coupler, introduced in 1969 [21, 22]. Nitinol solved the problem of
`coupling hydraulic-fluid lines in the F-14 jet fighter built by the Grumman Aerospace
`Corporation. Grumman engineers were seeking an alternative to the difficult task of
`joining lines that lie close to the aircraft’s aluminum skin. Raychem, which had wide
`experience in heat-shrinkable plastics, proposed a coupling in which a low-TTR
`(below –120 (cid:176) C; –184 (cid:176) F) Nitinol alloy was fabricated at room temperature (austenite
`phase) to the final deployed coupling dimensions. To produce the desired coupling
`effect the coupler was placed in a liquid nitrogen bath (martensite phase) and while
`there, the coupler was radially expanded. This was accomplished by forcing an
`oversize tapered mandrel longitudinally through the coupler bore. When continually
`cooled in liquid nitrogen, the coupler remained stably expanded. Coupling two
`sections of hydraulic pipe was then accomplished by simply inserting the pipe ends
`into the expanded Nitinol coupler and allowing the coupler to warm to its near
`original, or memory, diameter. The radial contraction of the coupler, combined with
`the very high associated force, provided a continuously clamping and totally sealed
`joint at well below the required –120 (cid:176) C (–184 (cid:176) F) temperature [23]. In this Nitinol
`application the TTR was designed to be less than –120 (cid:176) C (–184 (cid:176) F) [15], which was
`the required minimum operating temperature specification. These proven couplers are
`currently being used to join hydraulic tubes in the F-14 fighter aircraft as well as in
`many other similar industrial applications [21].
`
`COOK
`Exhibit 1019-0010
`
`

`

`1 1 / V O L . 2 , N O . 2
`T H E C H E M I C A L E D U C A T O R
`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
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`I S S N 1 4 3 0 - 4 1 7 1
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`S 1 4 3 0 - 4 1 7 1 ( 9 7 ) 0 2 1 1 1 - 0
`
`FIGURE 4. DR. GEORGE ANDREASEN DISPLAYING NITINOL WIRE THAT HE ADAPTED FOR ORTHODONTIC USE.
`NITINOL ORTHODONTIC DEVICES REQUIRE FEWER READJUSTMENTS THAN THEIR STAINLESS STEEL
`COUNTERPARTS [24].
`
`Another early use of Nitinol was in orthodontic bridge wires [24]. The late George B.
`Andreasen, D.D.S. of the University of Iowa developed Nitinol for use in orthodontics
`(Figure 4). In standard binding tests Andreasen found that Nitinol wires had a
`recoverable strain that was ten or more times that of stainless steel. The large
`recoverable strain, combined with a low elastic modulus (stress divided by strain)
`means that only one Nitinol wire is needed for most of the teeth-straightening
`procedure, even for badly maloccluded teeth, as opposed to the continuous changing to
`thicker and thicker stainless steel braces as the teeth are gradually brought into line.
`Andreasen wrote to Buehler after Buehler’s present wife had undergone some
`orthodontic work [26]:
`
`The dignity you are still receiving has spread around the world in your
`development of the alloy Nitinol. If it hadn’t been for you, your wife would be
`treated with stainless steel wire. If you had not sent me the 3–foot piece of
`Nitinol wire, I could not have applied it to orthodontics. In fact, I’ll be in your
`debt forever.
`
`COOK
`Exhibit 1019-0011
`
`

`

`1 2 / V O L . 2 , N O . 2
`T H E C H E M I C A L E D U C A T O R
`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
`
`I S S N 1 4 3 0 - 4 1 7 1
`h t t p : / / j o u r n a l s . s p r i n g e r - n y . c o m / c h e d r
`S 1 4 3 0 - 4 1 7 1 ( 9 7 ) 0 2 1 1 1 - 0
`
`With improved manufacturing techniques the commercial use of Nitinol increased
`during the 1970s and 1980s. Nitinol was incorporated into medical products, safety
`products, military products, and even ladies’ undergarments.
`
`Medical Applications
`One revolutionary use of Nitinol in medicine has been in orthopedic surgery. In
`September 1989 the U.S. Food and Drug Administration (FDA) approved the use of
`Mitek Surgical Products’ Mitek Anchor, constructed of Nitinol. Presently, the most
`common way of treating torn ligaments and tendons is immobilizing the limb of the
`patient in the hope that tissue will grow back onto the bone. Another option is surgery
`involving screws, staples, and other devices which reattach torn muscles to bone. Most
`of the surgeries involving this type of hardware are expensive as well as quite invasive
`to the body, making them somewhat dangerous. Mitek’s anchor is a fraction of the size
`of the older devices and is implanted through tiny incisions. It is shaped like a tiny
`anchor with two arms that hook into the bones. What makes the design work is the fact
`that compressed Nitinol returns to its original anchor shape after it is squeezed through
`a tiny hole in the body and subsequently warms to body temperature (37 (cid:176) C or
`98.6 (cid:176) F). Until now, use of the anchor has been FDA-approved only for shoulder
`surgery, but Mitek is hoping for expanded approval for other orthopedic surgeries [27].
`
`Physicians in the former Soviet Union are using Nitinol splints, with which simple
`fractures can be mended several times faster than with conventional splints. The
`Nitinol splints not only hold the fractured bones in place more securely, but they also
`push the bones together so that the break heals more rapidly [28].
`
`Perhaps no field of medicine has been changed by Nitinol as much as cardiovascular
`surgery. In 1989 radiologist Morris Simon, M.D. of Boston’s Beth Israel Medical
`Center patented a design for a blood filter that can be set in a vein to trap blood clots
`without surgery [15]. These blood colts (pulmonary embolisms) kill about 200,000
`victims each year, and the process of surgically implanting blood filters is both
`dangerous and expensive. With the Simon–Nitinol filter, below-body-temperature–
`TTR Nitinol wires are preformed in the desired mushroom shape. They are then cooled
`and straightened well below body temperature. When inserted into a large vein through
`a catheter and warmed to body temperature, the Nitinol wires spring back into their
`original mushroom shape while the filter’s splay feet attach to the wall of the vein.
`
`COOK
`Exhibit 1019-0012
`
`

`

`1 3 / V O L . 2 , N O . 2
`T H E C H E M I C A L E D U C A T O R
`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
`
`I S S N 1 4 3 0 - 4 1 7 1
`h t t p : / / j o u r n a l s . s p r i n g e r - n y . c o m / c h e d r
`S 1 4 3 0 - 4 1 7 1 ( 9 7 ) 0 2 1 1 1 - 0
`
`FIGURE 5. DIAGRAM 1 SHOWS THE SIMON–NITINOL PULMONARY EMBOLISM FILTER PRIOR TO ITS INSERTION
`IN A CATHETER. THE FILTER’S STRAIGHT, PLIABLE FORM IS MAINTAINED BY A COLD SALINE SOLUTION.
`DIAGRAMS 2–5 SHOW THE FILTER CHANGING TO ITS CLOT-TRAPPING SHAPE AS IT IS WARMED TO BODY
`TEMPERATURE [31].
`
`Once deployed in position, the filter is capable of catching clots en route to the heart,
`holding them until they dissolve naturally. Figure 5 shows the filter as it changes from
`the straight wire shape to its parent shape [29–31].
`
`Cardiovascular surgeons in Moscow have devised a procedure using a Nitinol
`prosthesis to reinforce sections of blood vessels. A small Nitinol wire, introduced into
`a vessel, transforms to its spiral parent shape when it warms to body temperature [32].
`
`Many other areas of medicine are feeling the impact of Nitinol. Catheter Research
`Corporation of Indianapolis, Indiana is currently marketing a “steerable” catheter for
`the placement of medical microinstruments, drugs, and electrodes
`in blood
`vessels [33]. The electronically controlled tip of the catheter is made of Nitinol
`supplied by Innovative Technology International (ITI), the company that Frederick
`Wang founded after he left the government in 1980 [34].
`
`In his doctoral project at the University of Twente in Enschede, the Netherlands,
`mechanical engineer Marc Sanders has experimented with the use of Nitinol as a
`gentler method of correcting scoliosis, a lateral bending and twisting of the spine that
`in most cases develops in infancy or childhood. In severe cases surgeons try to force
`the spine to straighten by implanting a rigid rod that is screwed to the vertebrae.
`According to Sanders, “we can apply a corrective force over several weeks, instead of
`
`COOK
`Exhibit 1019-0013
`
`

`

`1 4 / V O L . 2 , N O . 2
`T H E C H E M I C A L E D U C A T O R
`© 1 9 9 6 S P R I N G E R - V E R L A G N E W Y O R K , I N C .
`
`I S S N 1 4 3 0 - 4 1 7 1
`h t t p : / / j o u r n a l s . s p r i n g e r - n y . c o m / c h e d r
`S 1 4 3 0 - 4 1 7 1 ( 9 7 ) 0 2 1 1 1 - 0
`
`the transient force obtained by traditional methods…. We can achieve a better
`correction,” changing the twist as well as the bend in the spine [35].
`
`Extracting foreign objects from human organs such as the ear canal often requires a
`physician to force a large and rigid instrument past the object to grasp it, which often
`poses grave risks to the organ. Earl Angulo, a researcher with the Goddard Space
`Flight Center, has designed an instrument that eliminates such risks by incorporating
`Nitinol in its tip. The device is constructed from a small, flat loop for easy insertion
`past the object lodged in the organ canal. Electrical current is passed through the wire,
`heating it until it resumes the previously programmed hook shape and allowing the
`physician to grasp and remove the object [36].
`
`Energy, Engineering, and the Military
`Wang now researches, among other applications, the possibility of using Nitinol as a
`source of energy. Because solid-state heat engines require nothing more than a heat
`source to generate power, they could become a very clean power source. ITI has
`studied the feasibility of power plants based on