Smart Wearable Devices

The smart wearables industry pursues lightweight, high-performance, biocompatible, and durable materials, which are highly compatible with the material properties of advanced ceramics. Alumina (Al₂O₃), zirconia (ZrO₂), silicon carbide (SiC), and silicon nitride (Si₃N₄) are gradually infiltrating the smart wearables market from high-end consumer products.

It is important to note that in the smart wearables sector, zirconia is currently the most widely used and mature, followed by alumina. Silicon carbide and silicon nitride are more at the cutting-edge exploration and specialized functional application stage.

In the smart wearables sector, the value of ceramic materials lies primarily in:

• Excellent texture and aesthetics: They possess a jade-like texture, glossiness, and a premium feel, far surpassing metal and plastic, satisfying the aesthetic demands of consumer electronics.
• Excellent biocompatibility: They are non-allergenic and non-toxic upon contact with the skin, ensuring long-term comfort and safety.
• High hardness and wear resistance: They offer exceptional scratch resistance (high Mohs hardness), maintaining a pristine appearance and withstanding daily wear and tear. Hypoallergenic and skin-friendly: It is inert to bodily fluids like sweat, less likely to cause skin allergies, and provides a cool, skin-friendly feel.
• Integrated structure and function: It can serve as both an exterior component and an internal functional component (such as an antenna window or heat sink substrate).

1. Alumina (Al₂O₃) - "Economical and Reliable Functional Components"
In smart wearables, it is primarily utilized for its high hardness, electrical insulation, and low cost.
Advantages: High hardness, wear resistance, good electrical insulation, relatively low cost, and mature processing technology.

Specific Applications:

• Watch Back Cover/Sensor Window: Used in the back cover of smart watches, its signal penetration (for wireless charging and biosensor light) is superior to metal, making it a key material for functions such as heart rate and blood oxygen monitoring.
• Buttons/Crown: As buttons or crowns on watches, it is wear-resistant and provides a differentiated texture. 
• Internal Insulating Substrate: Serves as a carrier substrate for microsensors or chips, providing insulation and support.

2. Zirconia (ZrO₂) - "The Look and Feel of High-End Wearables"
Currently, this is the most successful and well-known advanced ceramic in the smart wearables field, primarily used in high-end product lines.
Advantages: Metal-like toughness (unbreakable), jade-like texture, high gloss and wear resistance, excellent biocompatibility, and no signal shielding.

Specific Applications:

• Smartwatch Cases/Bezels: This is its core application, as seen in the Apple Watch Edition, Huawei Watch GT series, and the high-end Xiaomi Watch. It replaces stainless steel and titanium alloys, offering a lighter, more wear-resistant, more skin-friendly, and more luxurious alternative.
• Smart Ring/Bracelet Body: Used in emerging smart ring products, its lightweight, durable, and skin-friendly properties are ideal for devices that require long-term, seamless wear.
• Mobile Phone/Watch Integrated Back Covers: Some smartphones also use ceramic back panels to match the watch style, and their wireless signal penetration is superior to metal.

3. Silicon Carbide (SiC) - "Forward-Looking Thermal Management and Chip Core"
In wearable devices, it serves not as a structural component but as a core semiconductor material and ultimate heat dissipation material.
Advantages: Extremely high thermal conductivity (superior heat dissipation), wide bandgap semiconductor properties (high efficiency and voltage resistance).

Specific Applications:

• Micro-Efficient Power Chips: Future applications include ultra-compact power management chips and charging management chips within smartwatches. The high efficiency of SiC devices reduces energy conversion losses and heat generation, thereby extending battery life or enabling faster charging.
• Heat dissipation substrate for ultra-high power density devices: For future AR glasses or smartwatches with highly integrated and complex functions, heat dissipation from their main chips will become a bottleneck. SiC can be used as a highly thermally conductive heat sink or substrate, quickly dissipating heat and ensuring stable performance.

4. Silicon Nitride (Si₃N₄) - "Exploring Sensor and Structural Expert"
A material with excellent overall performance, SiC is still in the R&D and specialized application stages in the wearable field, but it holds enormous potential. Advantages: Excellent comprehensive mechanical properties (strong and tough), thermal shock resistance, excellent dielectric properties, and good biocompatibility.

Specific Applications:

• High-Performance Sensor Substrates: Can be used to manufacture microsensors requiring extremely high precision and stability, such as high-precision pressure sensors or carriers for inertial measurement units (IMUs). Its low deformation and high stability help improve sensor accuracy.
• Ultra-Durable Structural Parts: For industrial-grade or specialized smart wearable devices (such as those used in outdoor adventures and military applications), silicon nitride's high strength and toughness can be used to manufacture the most vulnerable casing components, providing ultimate protection.
• Subcutaneous Implantable Sensor Packaging: Silicon nitride's extreme biocompatibility and stability make it an ideal packaging material for future long-term implantable health monitoring devices.