Why Microfluidic Chip Designers Are Excellent Tetris Players: The Game of Wafer Based Processing

When developing microfluidic chips or other precision components, every detail matters, but one aspect is often overlooked: the size of the chip. Have you ever considered how much unused space is wasted on a wafer when your chip is larger than necessary for the fabrication of microfluidic devices? This wasted space directly translates into higher costs per chip and lower output. For companies dependent on scalable, cost-effective production processes, this can be a significant challenge.

If you’ve ever played Tetris, you know how important it is to place each block as efficiently as possible. The fewer empty spaces you leave, the better you perform. Wafer processing works in a similar way: the more chips you can 'fit' on a wafer, the more efficient the production process, and the lower the costs per chip. By optimizing chip sizes, you can better utilize the wafer’s space and significantly increase output. In this article, we explore the benefits of reducing chip sizes and how a simple adjustment can lower production costs without needing to overhaul your entire manufacturing setup.

Maximizing Wafer Efficiency in Microfluidic Chip Production

Wafers form the basis of every microfluidic chip production process, regardless of the material used. Whether it’s glass, silicon, or polymers, the production processes are all adapted to work with standard wafer sizes. This makes wafers a crucial element in the mass production of microfluidic chips and other precision components. Standardizing wafers within the industry ensures that both design and production can proceed smoothly, no matter the complexity or variability of the designs produced on the wafers.

A wafer is essentially a thin disc of material used as a substrate onto which microstructures and circuits are are grown, etched, cut, or embossed. The most commonly used wafer sizes are typically 100 mm, 150 mm, and 200 mm in diameter, depending on the production processes and materials used. These standards make it possible to efficiently fabricate microfluidic devices and use systems specifically tailored to these sizes.

Each type of material used in production has unique properties that affect how it is processed on a wafer:

• Glass wafers provide several benefits, including chemical inertness, optical clarity, and mechanical stability. They are commonly used in applications requiring high precision and durability, particularly in the life sciences. One key feature is their isotropic etching behavior, which results in rounded microfluidic channels.

• Silicon wafers are fundamental to the semiconductor industry due to their excellent electrical properties. They exhibit non-isotropic behavior, allowing for straight walls, as seen in DRY etching techniques.

• Polymer wafers Polymer wafers are frequently chosen due to their inexpensive material cost, particularly in applications that require disposable materials, such as point-of-care diagnostics. These polymers are typically embossed, making it easier to produce large volumes in a standardized way. Working with polymers also provides more design flexibility because it is possible to employ formats other than wafers. Molding occurs at the piece level rather than the wafer level, so microfluidic chip sizes may vary depending on the mold's dimensions. Other processing processes, like as milling or 3D printing, may be employed depending on the maturity of your product.

Why the Size of Your Microfluidic Chips Matters

The size of the chips placed on the wafers determines how many chips can be produced per wafer and has a direct impact on the cost per unit. As seen in the image below, larger chip sizes result in fewer chips per wafer and more unused space.

Smaller chips lead to higher output per wafer, as more chips fit on the wafer. By optimizing the chip size, this space can be better utilized in the fabrication process, resulting in lower costs and higher output per wafer. Our designers understand this crucial aspect and can think ahead during the early stages about wafer optimization and possible adjustments to chip designs.

Practical Strategies for Optimizing Wafer-Based Microfluidic Chip Production: Design Analysis, Cartridges, and Multi-Design Processing

Improving Your Current Design Analysis

Optimizing chip sizes begins with a thorough evaluation of your current design. It is essential to assess where there is room for improvement without compromising functionality. By critically examining the existing chip dimensions, companies can often find opportunities to make the design more efficient. Our designers understand this important aspect and can already be involved in the early stages to think about wafer optimization and potential design adjustments. This ensures that the chip size is optimized from the design phase, leading to lower production costs and higher output.

Reduce Production Costs with Cartridges

Cartridges, typically made from plastic, play a crucial role in optimizing microfluidic chips. They provide a protective housing for more delicate materials like glass and silicon, making it easier to work with these brittle components. This approach not only enhances durability but also allows for smaller chip designs, which can lead to reduced production costs.

Beyond protection, cartridges offer several practical benefits. They improve integration with existing systems, simplify chip reading, and fit neatly into instruments. Many cartridges can also incorporate barcodes or other forms of information, making them ideal for automated procedures.

This cartridge-based approach is widely used in various fields where microfluidic chips are essential for analysis. For example, the GeneChip™ from ThermoFisher demonstrates this concept well. Its cartridge design allows for a smaller glass component, enabling multiple chips to be produced on a single wafer and significantly reducing costs. Another interesting case is Micronit's thin-bottom flow cells. These cleverly transform smaller-sized flow cells to fit a standard microscope slide format. Both examples show how thoughtful design choices can lead to more cost-effective and practical production methods. They're not just about making the chips smaller - they're also making the entire process smarter, safer, and more efficient.

Multiple Designs on One Wafer

One of the advantages of working with wafer sizes is the ability to process multiple chip designs on a single wafer. This offers companies flexibility during the testing phase, as they can place different design prototypes on one wafer and introduce variety into their tests. By smartly varying different parameters between the designs, a DOE (Design of Experiments) can be performed within one production run. Companies can quickly gain insight into which designs are the most efficient.

However, there are some limitations. Due to processing the entire wafer in one step, feature depths must be uniform across the wafer. However, you can vary the following dimensions:

• Length of the channels/structures
• Width of the channels/structures
• Number of channels/structures
• Spacing between the channels/structures

Our designers can guide companies from an early stage in optimizing wafer layouts, processing multiple designs on a single wafer to maximize testing possibilities while minimizing costs. For example, with five designs, you can get 10 chips per design or opt for 20-10-10-5-5 chips per design. See our the example on the wafer below. This can be interesting if you product is still in protoyping phase, so you can easily generate multiple versions of your designs. 

Why Early-Stage Design is Critical for Long-Term Success

Although the cost savings from reducing chip sizes may not be immediately noticeable in the short term, they become a crucial factor in the long term, especially when scaling up to higher production volumes. If companies decide to scale, an optimized design will ensure smooth production without unnecessary adjustments or extra costs. By investing in chip size optimization from the start, you enhance the scalability and success of your product. The cost per chip becomes essential to the success of your business case. It is therefore wise to consider optimizing chip sizes early on to prepare for future growth.

Start developing custom Microfluidic Chips with Micronit

At Micronit, we have extensive expertise in both design for manufacturing and the actual production of microfluidic chips. We advise our clients early on about the design of their chips, the use of cartridges, and how these can be integrated into their instruments. This not only results in short-term cost savings but also offers long-term benefits in terms of efficiency and scalability.