Smart Material Solve Contradictions
Editor | On 02, Feb 2009
By Darrell Mann
The value of smart material comes from its contradiction-solving abilities; linking the contradiction-solving material to a specific market need is critical to commercializing the product. The paper discusses the theoretical basis behind the importance of contradiction resolving in innovation and shows that while many smart materials are ready for the market, the markets are not necessarily ready for them. The paper includes examples of how innovators matched smart material capabilities to real contradiction-eliminating market needs.
TRIZ, phase change, non-linear, contradiction, inventive principles
The designer of a suspension system for an automotive application faces a difficult choice when specifying the optimum type of damping fluid. Sometimes the requirement is for a high viscosity fluid and sometimes it is for low. When the designer makes the trade-off calculations choosing the right viscosity of fluid, they miss an innovation opportunity, since the ideal damping fluid would possess both high and low viscosity.
Similarly, the designer of a bullet-proof vest must choose an optimum material that is stiff, yet flexible. Every time designers optimize they miss an opportunity to create a breakthrough ideal solution. Designers do not traditionally consider conflicting design criteria – materials that are viscous and non-viscous, flexible and stiff, big and small, red and blue – and, therefore, rarely think beyond design strategies that optimize material properties. Smart materials − like electro-rheological fluids, shape-memory alloys or thermo-chromic inks − present engineers and designers with potential paradigm-changing design solutions, because they offer solutions to these contradictions.
These smart materials, however, often come from academic research programs, which frequently results in technologies that cannot be successfully marketed. University laboratories rarely allow students to study the full-scale manufacturing capabilities for a smart material, and it is often difficult to see or control a particular application of the basic platform technology. The problem leads to materials viewed by industry as too expensive and unclear intellectual property situations. Another problem is that patents on a basic materials platform technology are bound by the same rules as patents for specific applications of the platform technology – patenting the platform technology buys 17 years of protection. In too many situations 17 years is insufficient for the patent owners to make a return on their investment.
The result is a gulf between research and commercialization with neither the industry nor industrial worlds asking the right questions. A previous study indicated the average return for applied university materials research is approximately three dollars for every $100 invested.1 As an investor this figure might indicate that money is better spent elsewhere. There are ways to better understand the root of a problem and develop suggestions for bridging the gulf. The discussion begins on the industry side of the equation with designers that operate with an “optimum,” as opposed to “ideal,” mindset. By using the inventive principles defined in TRIZ (Theory of Inventive Principles) researchers can design ideal smart materials.
Example One: Wrist Replacement
Figure 1 shows an X-ray of a typical wrist replacement. Usually prompted by chronic arthritis, wrist replacement surgery has one of the worst track records for durability among joint replacements. Of the approximately 30,000 wrist replacement operations in the United Kingdom every year almost half are replacements of previous replacements that have failed.
A key problem is that while the replacement uses a lot of metal, there is not much bone to hold it. The problem is exacerbated because unlike, for example, hip replacements, wrists cope with wider ranges of loads. A hip joint is usually in compression, and when it is in tension the load is limited to the weight of the leg. A wrist joint, however, regularly experiences both tension and compression loads that can exceed the weight of a person’s body.
Although wrist replacement joint engineers might not explicitly recognize it, they face a challenging contradiction with the tapered pin inserted into the radius – the tapered pin possesses both positive and negative qualities. When the joint is compressed − for example, when doing a push-up − the weight should be distributed over as much of the taper as possible to avoid splintering the radius. Conversely, when the joint is in tension − for example, when doing a pull-up exercise − the taper is a negative, because the pin could easily dislodge. By recognizing that a taper is good under compression, an optimization-focused design strategy sets about optimizing the taper angle. When the designer starts looking for the “optimum” solution he often misses the “ideal” solution and fails to innovate.
Figure 2 illustrates what a contradiction aware designer might see when looking at a wrist replacement problem:
It is difficult to contemplate a problem statement that calls for a design solution that has a taper and does not have a taper. But, that is exactly what the designers must consider when creating a breakthrough solution to the problem. TRIZ practitioners often study the contradictions in search of the ideal solution.
Figure 2 offers the problem solver several contradiction resolution opportunities.2 Each of the six lines in the picture represents a conflict or contradiction. Fail to solve one of them and five other possibilities remain. If the designer started with the “taper/no taper” physical contradiction, she would immediately face the usual separate-in-space, separate-in-time, etc., strategies. These strategies have been complemented with a model allowing a problem solver to map the eligible separation strategies to the inventive principles most likely to help resolve the contradiction.3 The eventual model is illustrated in Figure 3.
For the wrist replacement “taper/no taper” problem, the time, space and condition resolution strategies appear to be possible, and so the place to look for the most relevant inventive principles is at the center where the regions intersect. The most likely principles to solve the wrist replacement problem – based on previous problem solvers – are principles 2, 3, 4, 5, 13, 22, 25 and 35.
Principle 35, parameter changes, points problem solvers in the direction of smart material solutions. Principle 35 is simultaneously the most frequently recommended inventive principle and the one least well applied by problem solvers.4 When applied to the “taper/no taper” problem it is easy to see why simply telling a designer to change one of the design parameters is usually not effective. The biggest misinterpretation of this principle is that it is often viewed as a call to optimize a parameter, whereas in fact – since TRIZ is fundamentally not about optimization – it is a call for problem solvers to adjust parameters far enough that a non-linear shift in performance occurs. Figure 4 shows an example of the way this strategy is most effectively applied.
Having made the connection to non-linear shifts, designers must determine what parameters need to be shifted. Look at Figure 2 and examine what changes between the two extremes of the contradiction − what changes between tension and compression in the wrist joint? For one thing, the loading switches from negative to positive. Strain also changes, and if strain is changing, so is the size of the hole in the bone. Stress is changing, which means pressures are changing.
Next, the designers need to explore if any of these changes are relatively different between the bone and the metal replacement joint. Any differences between the two materials may cause problems. There are many differences between the properties of bone and titanium, including differences in the stress-strain characteristics. These differences impact loading transitions from compression to tension. Ultimately, the differences reduce down to a difference in Poisson’s ratio characteristics. According to The Engineering Tool Box, Poisson’s ratio is the ratio of the relative contraction strain to the relative extension strain. The Poisson’s ratio behavior under tension of bone is the exact opposite of that of titanium and other metals: stretch bone and initially it gets fatter (i.e., it has a negative Poisson’s ratio). Stretch titanium and it gets thinner (i.e., it has a positive Poisson’s ratio).
Having found differences between what existed in the original healthy joint and what the surgeon is going to replace it with, and having picked up the idea of transitioning boundaries as a means of solving contradictions, the designers are in a position to conduct a targeted search for a smart material solution. The ideal smart material solution will be one that under tension achieves a negative Poisson’s ratio and under compression achieves a zero or slightly positive ratio.
Auxetics are materials that have a negative Poisson’s ratio and become thicker when stretched.6 These auxetic materials and/or structures, if appropriately configured, might work in joint replacements. Researchers have been studying auxetic structures that can vary their Poisson’s ratio properties under different conditions, but no one has made the connection between the problem and this potential solution. From the designer’s perspective it is because the wrong problem has been specified.
A Generalized Model
The wrist replacement contradiction is by definition a mechanical problem. Any smart material solution to this problem requires the material to “respond” to different conditions in different ways. The important question is “what type of response does this situation require?”
The next question is “what is changing that can act as a stimulus to create the desired response?” In the wrist replacement problem, the primary stimulus is load. Changing the load, therefore, acts as a stimulus that triggers a changing Poisson’s ratio response − a mechanical stimulus is used to trigger a mechanical response.
Thinking in this stimulus-response manner allows innovators to simply and effectively classify smart material solutions. The table presents the results of arranging known smart materials in this way. Across the top of the table is a range of different responses a designer might wish to achieve. This is usually where to start when looking at the table, since it focuses on the desired outcome, and identifies the type of problem being solved. The stimulus column on the left side of the table prompts the user to consider what is changing or could be changed in the system to trigger the desired response. The range of different classes of stimulus reminds users there are a number of possible options. In the wrist replacement problem, as in any situation where designers are trying to create an ideal solution, the idea is to use a stimulus already present in the system. If there is no existing stimulus, there may be things to add to the system.
|Known Intelligent or Smart Resources|
|Magneto-electronics, spin-electronics, spintronics||Electro-chromic, electro-luminescent, electro-optic, piezo-chromic, Kerr effect, Pockel effect||Thermo-electric (Peltier)||Piezo-electric, electro-strictive electro-rheological electro-kinetic||Electrolysis, electro-chemical, bio-electric, electro-migration|
|Magneto-electronics, spin-electronics, spintronics, Hall effect||Magneto-optic, piezo-chromic||Magneto-thermal||Magneto-strictive, magneto-rheological||Nuclear-magnetic-resonance, magneto-chemical|
|Photo-conductive||Opto-magnetic||Optical bi-stability||Photo-thermic||Opto-mechanical, photo-acoustic||Photo-chemical, photosynthesis, photo-catalyst|
|Thermo-electric, super-conductivity, radiometer effect, pyro-electric||Curie point||Thermo-chromic, thermo-luminescent||Shape-memory|
|Piezo-electric, electro-strictive||Magneto-strictive||Mechano-chromic, rheo-chromic||Rheopexic, auxetic, shear-thinning, dilatants, non-newtonian, pseudo-plastic|
|Magneto-chemical||Color-change, litmus, luminescence||Exothermic, endothermic||Catalysis|
The table offers a list of key words used to instigate and guide a more detailed Internet or patent database search to find actual solutions. In the wrist replacement case, the box at the intersection between desired mechanical response and input mechanical stimulus indicates that auxetics are already an established solution in some applications. The entries in the table comprise materials or materials’ systems where the non-linear phase-change behavior illustrated in Figure 4 has been achieved.
Example Two: Self-timing Egg
Figure 5 illustrates an example of a more simple use of one of the smart materials identified in the table – a self-timing egg. The incorporated smart material allows people to boil an egg and achieve the desired result – the perfectly cooked egg. Too often people cook their eggs using an “optimal” rather than “ideal” mindset and, therefore, often cook them incorrectly. Shifting from an optimization mindset to ideal thinking can be difficult.
Breakfast eaters have viewed the egg problem as an optimization problem, because everyone knows how they want their eggs cooked. Most people remember one optimal number (a four-minute egg) when, of course, no two eggs are the same and cook at the same rate. The self-timing egg solution effectively says, “Wouldn’t it be nice if my specific egg in my specific pan tells me how cooked it is?”
The desired response is “tells me.” The table presents a number of possibilities. Most likely the simplest of those possibilities, and certainly the choice made by the owners of the Figure 5 solution, is optical. The next question, then, is “what are the available stimuli that might trigger the desired response?” Again, as with the wrist replacement problem, innovators must look at what is changing in the system. Again, as far as the owners of the solution were concerned, the simplest and most obvious change is with the egg’s temperature.
Looking at the optical response versus the thermal stimulus in the table, the first answer in the list of possibilities is thermo-chromic, which is the solution adopted by the self-timing egg inventors. Or rather, almost − because what makes the solution especially powerful is that it contains two subtly different thermo-chromic inks, each with a slightly different color change trigger temperature. Hence, the word “soft” (as shown in Figure 5) is triggered at one temperature, and the word “hard” is triggered at another slightly higher temperature.
From the Material Scientist’s Perspective
In many ways the self-timing egg and the wrist replacement joint cases provide two ends of a spectrum for the materials scientist. In the wrist replacement case, the medical devices industry may be guilty of defining the wrong problem. But, a reason they have been thinking in optimization rather than contradiction-solving terms is because of the inherent difficulties in proving to the regulatory authorities that the proposed solutions are safe. It is easier for the industry to prove that tweaking the shape of a titanium pin is safe than to prove the safety of a new form or structure of titanium. Proving a new material is safe can involve several years of expensive validation testing.
Conversely, applying a bit of thermo-chromic ink to an egg-shell merely requires a connection between the solution and a real problem. If the designer gets the self-timing egg solution wrong, the consequence for the customer is an over-cooked egg. The joint designer, however, is responsible for the patient’s quality of life.
John Naisbitt, a renowned American author who focuses on future studies, wrote “don’t get so far ahead of the parade that no-one knows you’re in the parade anymore.”5 This quote gets to the heart of the scientist’s dilemma in the world of smart materials. When patents are filed the clock starts ticking for marketing and achieving a return on the investment that created the basic material. Unless applications can be marketed inside the 17-year window the material technology has limited value. Thermo-chromic inks are fundamentally simple and inexpensive, so their transition to market for a host of applications has been relatively simple. Auxetics, however, still do not have any commercial applications. Despite the often-profound benefits they present to designers in many situations.
Dow Corning and the Active Protection System (APS) material solution derived from research at Imperial College in London is successfully marketing a new material. See Figure 6.
APS is a material system that is flexible under low-loading conditions (top-left part of the figure), but becomes stiff when subjected to a high impulse load (top right). In terms of the table, APS achieves a mechanical response to a mechanical stimulus. The material is an example of a shear-thickening dilatants silicone coating.
The material has a potential role where the “flexible/stiff” contradiction is present. Having patented the basic platform technology the race is on to find appropriate applications for the technology. Being aware of the contradiction they are solving has allowed researchers to target numerous possible applications, the ultimate of which appears to be in bullet-proof vests. Proving the material is suitable for such a demanding application requires time and significant resources. A good strategy, therefore, is to identify shorter-term niche applications such as using the material in shin-pads for soccer players. Using materials in alternate markets also emphasizes the importance of innovation timing.
Manufacturing shin-guards may not be a reason to invest in APS material production, but it increases the visibility of the material. It also offers real world data on the durability and effectiveness of the material – information vital in deciding whether to use the material in more critical applications.
This author has worked with a number of universities struggling with the issue of successfully commercializing their smart material platform technology research. The problem almost always involves a contradiction, and as a consequence, thanks to TRIZ research, someone will already have solved the contradiction. Figure 7 highlights one of the frequently used solutions to the commercialization contradiction:
Everything in this picture stems from the 17 years bought by the original patent. An alternative is for universities to not patent their discoveries, but rather keep their smart material formulations a trade secret until the first commercial possibilities are close to fruition. If the material is patented the aim is to generate revenues that pay for the research that in turn permits new and better platform patents to be constructed. These new patents then move the 17-year window far enough into the future that the mainstream applications have sufficient time to begin generating revenues.
Putting it Together
The gulf between smart material solutions and successful commercial exploitation exists because materials scientists, designers and engineers frequently come to the story with the wrong mindset. Designers and engineers need to consider contradiction-solving as part of their job. They also need assistance making it easier to find possible solutions to the contradictions they find. The table serves as a first step toward making a more direct connection between contradiction type and available solutions.
For materials scientists, the challenge is more about managing the transition from basic material technology to successful commercialization. All dilemmas are contradictions, and all contradictions can be solved. The key to their resolution in the case of smart materials has to do with finding sufficient high-value niche applications to generate sufficient revenues enabling the research that will open up mainstream applications.
- Graff, G.D., “Managing University and Government IP,” Commercialization and Technology Transfer Seminar, “Leveraging IP for Wealth Creation,” Kuala Lumpur, December 2007.
- Mann, D.L., “Evaporating Contradictions: Physical and/or Technical,” The TRIZ Journal, March 2007.
- Systematic Innovation E-Zine, “Re-Thinking the Physical Contradiction Solution Strategies,” Issue 76, July 2008.
- Systematic Innovation E-Zine, “Effective Use of Principle 35,” Issue 58, January 2007.
- Naisbitt, J., Mindset: Reset Your Thinking and See the Future, Collins, 2007.
- The Engineering ToolBox, http://www.engineeringtoolbox.com/poissons-ratio-d_1224.html
This paper was originallypresented at the European TRIZ Association’s TRIZ Future 2008 meeting in Enschede, NL.