Smart materials

Ahmed Samy

28 Nov, 2023

Dealing with smart people make your life easier and more comfortable, but how about dealing with smart materials can interact with external environment and respond to external stimuli.

What are smart responsive materials?

Smart materials, also known as responsive materials or intelligent materials, are materials that can interact with surroundings and have the ability to change their properties in response to external stimuli, such as mechanical stress, temperature, light, pressure, PH, or electric/magnetic fields. These materials can exhibit reversible changes, meaning they can return to their original state after the stimulus is removed.

Smart materials have cognitive responsiveness, rapid perceptiveness, swift reactivity, high efficiency, energetic vibrancy, and intellectual acumen. So we say this materials can think on their own.

The field of smart materials has significant implications for various industries, including aerospace, healthcare, robotics, consumer electronics and smart textiles.

Note that:

Smart materials are able to:

receive information.
analyze and decide.
act on the decision.

What are the basic components of a smart system?

There are 3 basic components of smart system:

Sensor.
Processor.
Actuator.

Note that:

Smart concrete building is the best example on the smart system:

There are optical fibers embedded in concrete these are sensors.

There are smart wires which can automatic shrink and expand these are Processors.

There are fillers preventing crack propagation these are Actuators.

What are types of smart materials?

1. Shape Memory Alloys (SMAs)

A type of alloy that retains its initial cold-forged form and can recover this shape upon heating or subjected to a specific stimulus.

Shape Memory Alloys (SMAs) possess the capability to restore their original dimensions and structure upon cooling, achieved through phase transitions.

Note that:

Nitinol (nickel-titanium alloy) is a well-known SMA.

2. Piezoelectric Materials

Materials that generate an electrical voltage in response to applied mechanical stress or pressure and can also deform when subjected to an electric field.

A piezoelectric transducer is connected to an LED. The LED momentarily illuminates upon the device being flicked, indicating the generation of electricity due to stress and strain.

Piezoelectric materials are used in sensors, actuators, and energy harvesting devices.

Note that:

The piezoelectric effect is a phenomenon that correlates mechanical stress with an electric voltage within solids.

In the realm of physics, the piezoelectric effect establishes a connection between mechanics and electrostatics.

3. Thermochromic Materials

These materials change color in response to temperature variations. They are used in applications like "smart" windows that can adjust their tint based on sunlight intensity, indicating temperature changes, or creating visual effects.

4. Electrochromic Materials

Similar to thermochromic materials, electrochromic materials change color, but the trigger here is an applied electric voltage. They are used in smart windows, displays, and rearview mirrors.

5. Shape Memory Polymers (SMPs)

Similar to SMAs, these polymers can return to a predefined shape after being deformed, usually through heat activation. SMPs are used in applications like self-healing materials and deployable structures.

6. Hydrogels

These are materials that can absorb and release water while maintaining their structural integrity. They are used in applications such as drug delivery, wound care, and soft robotics.

7. Photochromic Materials

These materials change color when exposed to light, commonly found in transition lenses for eyeglasses.

8. Magneto-strictive Materials

These materials change shape in response to a magnetic field. They are used in precision motion control systems and sensors.

9. Self-Healing Materials

Have the ability to repair damage autonomously, extending the material's lifespan. Used in aerospace, automotive, and consumer goods.

10. Smart Polymers

Polymers that can change their properties (shape, stiffness, etc.) in response to environmental factors like temperature, pH, or other stimuli.

11. Smart Textiles

Fabrics with integrated smart materials, such as conductive fibers for wearable electronics or shape-changing textiles.

12. Phase Change Materials (PCMs)

Absorb and release thermal energy during phase transitions, regulating temperature. Used in energy-efficient building materials and cooling applications.

How do smart materials work?

Smart materials work by exploiting the unique properties and responses of certain materials to external stimuli, allowing them to change their characteristics in a controlled manner. The mechanism behind each type of smart material depends on the specific properties of that material and the nature of the stimulus. Here's a more detailed explanation of how some common smart materials work:

Shape Memory Alloys (SMAs):

SMAs have two distinct phases: austenite (high-temperature phase) and martensite (low-temperature phase). The shape memory effect is based on the reversible phase transformation between these phases.

When the SMA is in the martensitic phase and is deformed (e.g., bent), it can "remember" this deformed shape. Applying heat to the SMA causes it to transition back to the austenitic phase, leading to the material returning to its original shape.

Piezoelectric Materials:

Piezoelectric materials have a crystalline structure that generates an electric charge when subjected to mechanical stress or pressure, a phenomenon known as the piezoelectric effect.

Conversely, applying an electric field to these materials can cause them to deform or change shape. This property is used in actuators, where the change in shape is used for various purposes.

Thermochromic Materials:

Thermochromic materials contain molecules that undergo reversible molecular rearrangements in response to temperature changes. These rearrangements result in a change in the material's absorption and reflection of light, causing a color change.

Electrochromic Materials:

Electrochromic materials change color in response to an applied electric voltage. This change in color is due to the migration of ions within the material, leading to a reversible oxidation or reduction reaction that alters the material's optical properties.

Shape Memory Polymers (SMPs):

SMPs are typically made of polymer chains that can form temporary cross-links in response to a certain stimulus, such as heat.

When heated above a specific transition temperature, the polymer chains can rearrange, allowing the material to return to its original shape.

Hydrogels:

Hydrogels can absorb and release water while maintaining their structure due to their network of hydrophilic polymer chains.

The absorption and release of water cause the hydrogel to expand or contract, which can be utilized for controlled drug release or actuation in soft robotics.

These are just a few examples, and there are many other smart materials with unique working principles. The key idea is that these materials have specific responses to external stimuli, and engineers and scientists leverage these properties to design innovative products and solutions.

Properties of smart materials

Properties of smart materials include:

Responsive to Stimuli

Smart materials can change their properties in response to external stimuli like temperature, pressure, light, or electric/magnetic fields.

Reversible Changes

They can undergo reversible changes and return to their original state once the stimulus is removed.

Autonomous Action

Some smart materials can perform actions without external control due to their intrinsic properties.

Adaptability

Smart materials can adapt to changing conditions, making them suitable for various applications.

Sensitivity

They exhibit sensitivity to specific triggers, enabling precise control over their behavior.

Mechanical Flexibility

Many smart materials can change shape or mechanical properties in response to stimuli.

Energy Conversion

Certain types of smart materials can convert one form of energy (like mechanical stress) into another (like electrical energy).

Self-Healing

Some smart materials have the ability to repair minor damage, extending their lifespan.

Efficiency

Smart materials often perform tasks more efficiently than conventional materials.

Innovative Applications

These materials enable unique and innovative applications, ranging from medicine to electronics.

Controlled Actuation

They can actuate or move based on external input, leading to applications in robotics and precision control.

Versatility

Smart materials have diverse applications across industries due to their diverse responses.

Reduced Maintenance

Their self-repairing abilities and adaptability can reduce the need for frequent maintenance.

Environmental Interaction

Some smart materials respond to environmental changes, aiding in monitoring and sensing.

Integration

They can be integrated into complex systems, enhancing their overall performance.

Customizability

Smart materials can be engineered with specific responses for tailored applications.

Precision

They enable precise control and manipulation in various fields, from medical devices to aerospace.

Overall, smart materials' distinct properties make them valuable for developing advanced technologies and improving various aspects of our lives.

Applications of smart materials in daily life

Smart materials have a wide range of applications in daily life, and they continue to play an increasingly significant role in various industries. Here are some common and emerging applications of smart materials that you might encounter in your daily life:

Smartphones and Tablets

Touchscreens: Capacitive touchscreens in smartphones and tablets use transparent conductive materials, often based on indium tin oxide (ITO), to detect touch gestures.

Scratch-resistant coatings: Some screens feature smart coatings that can self-heal minor scratches, helping to maintain display quality.

Smart Clothing and Wearables

Shape memory alloys and polymers: These are used in clothing with adjustable fit (self-adjusting waistbands, shoe laces), as well as in innovative designs for self-fitting bras, etc.

Activity trackers: Wearable devices utilize sensors and flexible materials to monitor activities, heart rate, and other health-related metrics.

Automotive Industry

Smart windows: Electrochromic windows that can change tint to regulate the amount of sunlight and heat entering the car, improving comfort and energy efficiency.

Tire pressure sensors: These sensors use piezoelectric materials to monitor tire pressure, alerting the driver to low pressure, improving safety and fuel efficiency.

Healthcare and Medical Devices

Shape memory alloys: Nitinol is used in stents, which can be compressed for insertion and then regain their shape at the target site.

Drug delivery systems: Smart materials, like hydrogels, can be used for controlled and targeted drug release, ensuring effective treatment.

Artificial muscles: Electroactive polymers (EAPs) are being researched for use in prosthetics and robotics to create more natural and responsive movements.

Energy Efficiency

Smart windows: As mentioned earlier, these windows can reduce energy consumption by regulating indoor temperatures, reducing the need for heating or cooling.

Energy harvesting: Piezoelectric materials can convert mechanical vibrations (e.g., from footsteps) into electrical energy, which can be used to power low-energy devices.

Consumer Electronics

Smart displays: OLEDs (organic light-emitting diodes) and other advanced displays use various materials to provide better image quality, lower power consumption, and flexibility.

Vibration feedback: Haptic feedback in devices like smartphones and game controllers uses piezoelectric actuators to create tactile sensations.

These examples demonstrate how smart materials are integrated into various aspects of daily life, enhancing functionality, comfort, energy efficiency, and overall user experience. As technology advances, we can expect to see even more innovative uses of smart materials in our everyday products and environments.