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The Vary Principle in Functional Innovation

By Tojin T. Eapen

"The world often resists change, but it is ultimately change that drives progress. "

In the above quote, Charles Kettering points out that without change, there can be little advancement. The principle of dynamism, or the "vary principle," is all about change and the ability of a system to adapt and respond to inputs by changing its attributes or characteristics.

Many systems around us are relatively static, such as tables, spoons, and curtains. However, more complex systems like helicopters and donut-making machines are more dynamic, moving and responding to inputs, sometimes even making noises. The computer is probably the most dynamic of human artifacts, with the ability to be programmed to respond to inputs in a specific way. Even the simplest life forms, like the Venus flytrap or the human eyelid, are more dynamic than the most complex human-made systems.

By applying the vary principle, we can make a system more "life-like," resulting in products that are easier to use, more attractive, and sometimes even safer. This way of thinking involves considering if a attribute or property of a product, system, or process can change based on an input, and using that information to come up with ideas for improving the system.

Identifying Changeable Attributes and Inputs

To start, we need to identify two things: the property or attribute that needs to be changed, and the input that will cause this change. For example, let's consider a simple kitchen knife. Some properties of a knife might include its weight, color, sharpness, strength, and shape. These properties are often relatively static, but we could intentionally design them to be alterable based on certain inputs. To do this, it can be helpful to gather user insights and consider any problems or issues that people might have with kitchen knives. For example, amateur chefs might accidentally cut their fingers, blades might become dull over time, or children might take the knives to their bedrooms and play with them. By considering these types of inputs, we can design a more dynamic kitchen knife that is able to adapt and respond to changing conditions.

Can any of these problems be solved by making a attribute more dynamic? For example, what if we designed a kitchen knife that changed color when it became dull, or one that reduced its sharpness on contact with skin? These ideas may not be practical, but thinking in this way can lead us to potential solutions. For instance, think of a kitchen knife with a handle that vibrated when the blade became dull, alerting the user to sharpen or replace the blade. This is just one example of how applying the dynamic principle can lead to innovative solutions to problems.

Of course, creativity and ingenuity are key when applying this principle to real-life problems. Identifying the right attribute to modify and the appropriate input to use is crucial in creating improvements. For example, in the case of the kitchen knife, changing the color might not be the most effective solution to the problem of dull blades. Instead, using the input of blade dullness to trigger a vibration or other alert might be a more practical and useful solution.

For example, consider a thermostat that is used to control the temperature in a home. The thermostat has a set point temperature that the user selects, and it is able to turn the heating or cooling system on or off to maintain that temperature. The input in this case is the ambient temperature in the room, which is constantly being measured by the thermostat's sensors. When the temperature falls below the set point, the thermostat triggers the heating system to turn on and warm the room. Once the temperature reaches the set point, the thermostat turns the heating off. In this case, the input (the ambient temperature) is simply a trigger that initiates a change in the system (the heating turning on or off).

On the other hand, consider a recipe for bread that requires yeast. The input in this case (the yeast) is not just a trigger, but is actually a key ingredient in the transformation that occurs during the bread-making process. The yeast is responsible for causing the dough to rise and become light and fluffy, and without it, the bread would not turn out as desired. In this case, the input (the yeast) is a key ingredient in the transformation of the dough into bread.

Four Types of Inputs

There are generally four types of inputs that can be identified: the user, time, external systems, and internal feedback. These inputs can be used to make a system more dynamic, allowing it to adapt and respond to different conditions.

User input a common way to vary an attribute. For example, a user might adjust the brightness of a flashlight or the volume of a speaker using a button or dial. Similarly, a user might adjust the firmness of a mattress or the intensity of a massage chair using a remote control or an app.

Examples of using the user as an input include smart home devices that can be controlled through a smartphone app, or vending machines that allow users to customize their orders. Time can be used as an input in a variety of ways, such as street lighting that varies in intensity based on the time of day, or automated irrigation systems that turn on and off based on the weather forecast. External systems can also be used as inputs, such as a security camera that uses facial recognition to identify known individuals, or a smart thermostat that adjusts the temperature based on the occupancy of a room. Internal feedback can be used to monitor and adjust the performance of a system, such as a car's onboard computer that adjusts the fuel-to-air ratio based on sensor readings.

Other examples of using inputs to make a system more dynamic include automated doors that open and close based on the presence of a person, or self-driving cars that use sensors and map data to navigate roads and avoid obstacles. By considering the various inputs that can be used to make a system more dynamic, we can come up with innovative solutions to problems and improve the user experience.

Time is indeed another way to vary an attribute, and the example of deodorant that changes smell over time is a good one. Here, the attribute being modified is the smell, and the input is time. Another example of a product that varies an attribute based on time is a self-watering plant pot. These pots have a reservoir of water that is gradually released over a period of time, allowing the plants to stay hydrated without the need for daily watering.

Another common input for modifying an attribute is external conditions. For example, a weather-resistant jacket might have an attribute like waterproofness that can vary based on the amount of rain or humidity present. Similarly, a thermos bottle might have an attribute like insulation that varies based on the temperature of the surroundings.

Internal feedback can also be used as an input to vary an attribute. For example, a car's air conditioning system might use a sensor to measure the temperature inside the car and adjust the output of the air conditioning accordingly. Similarly, a smart thermostat might use feedback from sensors to adjust the temperature of a home based on the presence of people or the level of sunlight.

User as an Input

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The idea of designing products where attributes change based on user input is not new, but it has gained popularity in recent years with the rise of technology and the increasing focus on user experience. There are many examples of products where attributes change based on user input, and they range from simple everyday items to complex systems.

One example of a product where attributes change based on user input is a smart thermostat. These thermostats use sensors to gather data about the temperature in a room and allow users to set the desired temperature. The thermostat then adjusts the temperature accordingly, using inputs such as the time of day and the user's preferred temperature settings.

Another example of a product where attributes change based on user input is a self-driving car. These cars use a variety of sensors and algorithms to navigate roads and avoid obstacles, but they also allow users to input their destination and preferences for things like speed and route. The car then adjusts its behavior based on these inputs, making it a dynamic product that changes in response to the user's needs.

There are also many examples of products where attributes change based on user input in the field of healthcare. One such example is a smart inhaler, which tracks a user's inhaler usage and provides feedback on their inhaler technique. This allows users to adjust their inhaler technique as needed, improving their overall health outcomes.

Another example of a product where attributes change based on user input in healthcare is a smart insulin pump. These pumps allow users to input their insulin needs and adjust the amount of insulin they receive accordingly. The pump then adjusts the insulin delivery based on the user's inputs, making it a dynamic product that changes in response to the user's needs

Time as an Input

The use of time as an input to vary or modify attributes can be seen in many different products. One example is with medication. Many medications have time-release features, where the active ingredients are released gradually over a certain period of time. This can be useful for maintaining a consistent level of medication in the body, or for ensuring that the medication is taken at regular intervals.

In the realm of home appliances, we can see time as an input in products like coffee makers and slow cookers. These appliances allow the user to set a specific cooking time, after which the appliance will automatically turn off or switch to a warming setting. This can be convenient for people who want to set it and forget it, and it can also help to prevent accidents or fires by ensuring that the appliance is not left on for an extended period of time.

One more example can be found in the world of fashion. Some clothing brands offer garments with patterns or designs that change over time. For example, a shirt might start out solid black, but after being worn for a certain period of time, the fabric might start to fade or the color might change. This can create a unique, one-of-a-kind look that is different from anything else on the market.

Time release technology is a pharmaceutical technology that allows medicine to be released into the blood over a longer period of time. This means that the patient would have to take their medication much less frequently. For example, instead of taking a pill every 4 hours, a time-release version of the same medication might allow the patient to take the pill once a day. This can be especially useful for people who have trouble remembering to take their medication, or for medications that have unpleasant side effects when taken in high doses.

Slow release fertilizers are another example of products that use time as an input to modify their attributes. These fertilizers are designed to release nutrients into the soil over a longer period of time, rather than all at once. This can be more efficient for plants, as it allows them to access the nutrients they need when they need them, rather than having a sudden surge of nutrients that they may not be able to use all at once.

There are many potential applications for time release technology beyond the examples mentioned above. For example, a slow release soda system in soft drink cans could allow the user to continue to enjoy the fizz of the soda for a longer period of time. Similarly, a slow release detergent system in a washing machine could allow the machine to clean clothes more effectively over a longer period of time, rather than using all the detergent at once. Wrigley's obtained a patent in 1990 for a structure that enables the slow release of the active ingredient inside a chewing gum [US Patent 4978537].

External Systems as Inputs

There are many products that use external systems as inputs to modify their attributes. One example of this is the solar panel. Solar panels are designed to convert sunlight into electricity, and they do this by using photovoltaic cells made of semiconductor materials. These cells are able to absorb photons of light and convert them into electricity, which is then used to power electronic devices or stored in a battery for later use.

The efficiency of a solar panel depends on several factors, including the quality of the cells and the amount of sunlight it is exposed to. However, solar panels can also be designed to optimize their performance based on external inputs. For example, some solar panels are equipped with tracking systems that follow the movement of the sun across the sky, allowing them to capture more sunlight and generate more electricity. Other solar panels are designed to adjust their angle and orientation based on weather conditions or the time of year, in order to optimize their exposure to sunlight.

Another example of a product that uses external systems as inputs to modify its attributes is the smart thermostat. These devices are designed to control the temperature in a home or office by adjusting the heating and cooling systems based on external inputs such as the weather, the time of day, and the occupancy of the building. Some smart thermostats are also equipped with sensors that detect the presence of people in a room, and adjust the temperature accordingly. For example, if a room is empty, the thermostat may turn off the heating or cooling to save energy.

Other examples of products that use external systems as inputs to modify their attributes include smart irrigation systems, which adjust the watering schedules of plants based on weather data, and smart lighting systems, which adjust the brightness and color of lights based on the time of day or the presence of people in a room.

Internal Feedback as Input

Products that use internal feedback as an input to modify their attributes can be found in a variety of industries and applications. One example of this is self-regulating heating systems, which use sensors to monitor the temperature of a room and adjust the output of the heating element accordingly. This ensures that the room stays at a consistent, comfortable temperature without the need for manual intervention.

Another example can be found in the automotive industry, where self-regulating brake systems use sensors to monitor the pressure and speed of the brake pads, and adjust their output accordingly. This helps to optimize braking performance and increase safety, as the brakes can respond more quickly and effectively to changing road conditions.

Other products that use internal feedback to modify their attributes include self-regulating irrigation systems, which use sensors to monitor soil moisture levels and adjust the amount of water being applied accordingly, and self-regulating ovens, which use sensors to monitor the temperature of the oven and adjust the heating element to maintain a consistent cooking temperature.

Input Substitution

Sometimes, interesting ideas can develop by considering if a different input could be applied in place of an existing one. This can allow for innovative solutions to problems and can lead to significant improvements in a system.

For example, a system engineer at a data storage firm might have been tasked with finding ways to improve the efficiency of the company's storage systems. One approach the engineer might take is to consider if a different input could be used in place of the existing one. In this case, the engineer might have noticed that the current system relied on time as the primary input for managing data storage and retrieval. By considering if a different input could be applied, the engineer was able to come up with a novel solution: changing the input from time to data churn, or the amount of data being accessed and moved within the storage system.

This approach can be applied to a wide range of systems and problems, from technical systems like data storage to more abstract concepts like business models or marketing strategies. By considering different inputs that could be used to drive change and improve a system, we can come up with innovative solutions and find new ways to solve problems.

This way of thinking is not limited to products alone. We can also consider how the properties of other types of systems can be changed to make them more dynamic. For example, we could think about how a business model or a service process could be made more responsive to changing conditions. This approach can also help us design marketing schemes that are engaging and appealing to customers.

Designing a Dental Cleaning System

Let's consider the example of designing a superior dental cleaning system. One approach we could take is to create a grid that identifies the various components of the system and the various attributes each component might have. For example, for the brush component, we might consider attributes such as bristle length, stiffness, and material. The paste component could have attributes like color, taste, active ingredients, smell, and consistency.

By considering the different attributes of each component, we can identify opportunities for improvement and design a more effective and efficient dental cleaning system. For example, if we are designing a toothpaste, we might consider using a natural, minty flavor that is pleasant to taste and leaves a fresh smell in the mouth. Or, if we are designing a toothbrush, we might consider using soft, flexible bristles that are gentle on the gums but still effective at removing plaque and food particles. By thinking about the various attributes of each component and how they interact with each other, we can design a dental cleaning system that meets the needs and preferences of users.

There are many ways that we can improve a dental cleaning product by considering how an attribute can vary based on input. For example, one attribute that we might consider is the color of the toothpaste. Here are a few potential inputs that could be used to vary this attribute:

  • Time: A toothpaste that changes color over time could be used to indicate the relative effectiveness of the active ingredients. For example, a toothpaste that starts off white but gradually turns blue as it's used could indicate that the active ingredients are being released and working to clean the teeth.
  • Bacteria levels: Another use for a toothpaste that changes color could be to indicate the level of bacteria in the mouth. For example, a toothpaste that starts off green but turns red as the level of bacteria increases could help users monitor the cleanliness of their mouth and adjust their oral hygiene habits accordingly.
  • pH levels: The pH level of the mouth can affect the health of the teeth and gums. A toothpaste that changes color based on the pH level of the mouth could help users identify areas that might need more attention or where they might be using too much or too little of the toothpaste.

Another attribute that we might consider when designing a dental cleaning product is the length of the bristles. One solution could be a design where the user can adjust the length of the bristles based on their preferences. This could be especially useful for people with sensitive teeth or gums, as they might prefer softer, shorter bristles.

Alternatively, we could consider a design where the length of the bristles adjusts automatically based on the structure of the mouth and teeth. For example, the bristles could be shorter in areas with more sensitive teeth and gums, and longer in areas that are easier to reach. This could help to ensure that the teeth and gums are being cleaned effectively and gently. By considering different attributes and how they can be varied based on different inputs, we can design dental cleaning products that are more effective and comfortable to use.

By considering how an attribute like the color of the toothpaste can vary based on different inputs, we can design a product that is more interactive and informative for users, helping them to better understand and take care of their oral hygiene.

We could also start with a well known problem and consider if a solution can be identified using the vary principle. One problem that many parents face is getting their children to brush their teeth for the recommended two minutes. One solution to this problem could be a toothpaste that changes color to indicate when enough time has passed. For example, Howard Wright, a dentist, invented the Vortex color changing toothpaste, which turns red when it's time to stop brushing. This helps kids to understand how long they should be brushing for and encourages them to brush for the recommended time. Another solution could be a toothpaste that turns sweet after five minutes of brushing. This could be a fun and rewarding way for kids to brush their teeth, as they'll know that they'll get a sweet treat once they've brushed for long enough.


There are many different ways that the attributes of spectacles can be made more dynamic. One simple example could be a design where the spectacles can be folded in the middle, making them more portable and easier to store. Another option could be a design where the length of the frame can be adjusted to fit the comfort of the wearer, allowing for a more customized fit.

One well-known example of dynamic glasses is those with photochromatic lenses, such as those manufactured by Polaroid Eyewear. These lenses change shades when exposed to sunlight, becoming darker to protect the eyes from glare. This is a useful feature for people who need to wear glasses all the time but also want to be able to wear them outdoors without having to constantly switch between regular glasses and sunglasses.

Other potential attributes of glasses that could be made more dynamic include the frame material, which could be changed to suit different weather conditions or personal preferences, and the shape of the frames, which could be made more adjustable to fit different face shapes. By considering how different attributes of glasses can be changed or varied based on different inputs, we can design more functional and comfortable eyewear for a wide range of users.

A bolder idea for dynamic spectacles would be lenses that dynamically alter their focal length based on the optical correction required for the wearer. Basil Wright patented a design for spectacles with adjustable focal lengths that could be adjusted by rotating a dial on the lens. This was intended for use in areas where access to opticians may be limited, such as in Africa.

Car Design

Car design involves extensive use of the vary principle, which involves considering if an attribute or property of a product, system or process can change based on an input. In the case of cars, this could range from adjustable components like steering wheels and seats to attempts at providing a highly dynamic driving experience for the user.

One way in which the vary principle is applied in car design is through the use of user inputs. For example, a car might load a certain user profile based on the driver or the occupants. This profile could contain information about the user's preferred music or common routes. The car might also activate certain safety mechanisms, such as a child lock or a secondary airbag, based on the presence of certain users inside the car.

Another way in which the vary principle is applied in car design is through the use of time inputs. For example, a car might adjust its speed based on the time of day or the weather conditions. It might also have a system that monitors the driver for drowsy behavior and sends a message or stops the car in the case of a detected issue.

External systems can also be used as inputs to modify attributes of a car. For example, a car might have an adaptive steering system that adjusts the steering based on the actions of other vehicles on the road. It might also have variable headlights that change in intensity, direction, or shape based on the external environment.

Internal feedback is another input that can be used to modify attributes of a car. For example, a car might have a variable transmission system that adjusts the gears based on the speed and acceleration of the car. It might also have a system that monitors the road and provides feedback to the driver to help them better manage speed.

To learn how leading Fortune Global 500 companies such as ABB, Bosch, Google, Samsung, and NetApp have used Innomantra's Functional Innovation Methodology to turbocharge their idea management process, schedule a meeting today at


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