Label-free cell sorting in microfluidics is a technique used to separate different types of cells without attaching chemical labels or dyes to them. Instead of tagging cells, it sorts them based on their natural physical properties while they flow through tiny channels (microfluidic devices). Cell sorting is an essential technique in cell biology research, as sample prep and in many diagnostic and therapeutic applications. Microfluidic cell sorting can provide gentile sorting methods with the benefit that it refrains from biochemical labeling of cells. Several microfluidic techniques provide solutions to this by making use of the intrinsic characteristics of cells like size, shape, electrical polarisability, or hydrodynamic properties.

What is label-free cell sorting?

Label-free cell sorting means there are no fluorescent dyes, antibodies, and magnetic beads attached to cells that need to be separated. Cells are separeted by their natural characteristics, while flowing through microscopic channels. The most common label-free cell sorting methods are:

• Inertial microfluidics
• Deterministic Lateral Displacement (DLD)
• Acoustic sorting
• Dielectrophoresis
• Filtration-based sorting

DLD: An asymmetrical array of pillars

One of the microfluidic label-free sorting techniques is deterministic lateral displacement (DLD). In short, this is a way to separate particles or cells in fluids by driving them through an array of regularly placed pillars. By positioning the pillars at determined angles, particles of different sizes are forced into different streamlines and are this way separated. The pattern of the array of pillars is determining the streamlines of the particles. If required, a relative high throughput can be achieved. Please contact Micronit if you have a specific need for this.

DLD in polymer

A quick examination of the blood is therefore of the essence. For this project, a thermoplastic polymer chip was developed that contains an array of pillars as small as 20 µm in diameter. The DLD sorting method, based on particle morphology, proved to be very useful.

To get a good impression of the DLD-process, take a look at this video, made by Stefan Holm, one of the project’s participants.

DLD in silicon/glass

At Micronit, DLD-chips are developed in silicon and glass. Both silicon and glass are known for their chemical and biological inertness. Besides, both materials can be cleaned from biological deposits, and are therefore very suitable to be reused. A hybrid combination of silicon and glass ensure the tiniest features, resulting in a sustainable and reliable chip. To test the functionality of the chip, fluorescent microparticles were used.

DLD-chip for general use

The goal of this project was to make a microfluidic DLD-chip that can be used for as many different applications as possible. This is a novelty, for up until now, DLD-chips were often developed for a dedicated purpose and specific devices. By choosing durable materials and making the chip suitable for general use, a multi-purpose, sustainable microfluidic DLD-chip was developed.