Lab-on-a-Chip

Mini laboratories for rapid pathogen detection

Lab-on-a-chip testing options are increasingly diverse, and their adoption continues to grow. Microfluidic test carrier systems are now used not only for detecting specific pathogens—such as those responsible for infectious diseases or dermatological conditions—but also in wastewater analysis. These systems can serve as automated analytical tools to monitor molecular biological processes in wastewater. During the pandemic, targeted wastewater surveillance proved effective in tracking the spread of SARS-CoV-2. These miniaturized laboratories offer faster and more efficient testing outcomes.

What is a lab-on-a-chip?

A lab-on-a-chip is typically a plastic cartridge containing multiple chambers and microchannels. It houses a variety of reagents—biochemical substances and solutions—that initiate an analysis process when a sample (such as blood, saliva, skin tissue, or even wastewater droplets) is introduced and precisely guided through the channels. The key innovation is that a full laboratory process takes place on a miniature scale within the cartridge. Whereas samples previously had to be sent to a lab and processed by technicians within a specific timeframe, results can now be obtained directly at the point of care—often within just minutes or hours.

RKT specializes in microfluidic test carrier systems and supports companies in turning their product ideas into production-ready products.

How are lab-on-a-chip disks manufactured?

The manufacture of microfluidic channels and chambers for a lab-on-a-chip involves highly complex geometries, often created using plastic injection molding. The channels enable the controlled transport of liquids and sample material through the chip, while the chambers serve as reaction sites.
Integrating RKT’s plastics expertise early in the design phase helps ensure that fluid flow and reactions function as intended later in the process. Customer-designed geometries may need to be adapted for injection molding to account for demolding requirements—critical for enabling proper part release from the mold and preventing internal material stress.

In toolmaking, the creation of fine microchannels demands the highest precision. RKT manufactures microstructures using precision milling and electrical discharge machining (EDM), with milling diameters as small as 0.1 mm—about the thickness of a sheet of paper. Laser and LIGA processes are also employed to achieve even finer structural details

Wie werden Lab-on-a-Chip-Disks hergestellt?

Everything depends on the right plastic

Choosing a suitable plastic is crucial for subsequent functionalities. The raw material must have the right viscosity for the injection molding of the microfine structures, and be absolutely inert so that no undesirable reactions occur with the biochemical material that will be integrated at a later point (including in the long term to ensure the cartridge has a long shelf life). RKT often uses COC plastics for diagnostic purposes, such as lab-on-a-chip systems, as they are highly transparent, have very low optical anisotropies, and are also biocompatible. Parts of the housing, on the other hand, are usually made from impact-resistant plastics such as ABS, PC/ABS, polyamides, or PBT.

All from a single source

The finished injection-molded cartridge components are just the beginning.
RKT offers the full value chain—from loading the cartridges with biological components to assembly and packaging.
Over the course of multiple projects, RKT has established robust processes that ensure reliable series production of lab-on-a-chip products. These include technically demanding steps such as liquid handling and the integration of lyophilized reagents.
In addition, RKT operates its own production line for microfluidic disks, allowing for immediate manufacturing with customized adaptations—without the need to first set up a new production environment.

The various process steps:

Pipetting in liquids

When it comes to liquid handling, the main challenge is the small quantities of liquid that have to be introduced into the plastic cartridges. These are often just a few microliters – droplets – that are pipetted into the tiny chambers with positional and repeat accuracy using robotic systems in a process known as microspotting. Incorrect dosing can cause malfunctions in the fluidics, so absolute precision is required. The cartridge with the liquids then passes through a drying oven in which the liquids evaporate, leaving the pure reagents in dried form, thereby preserving the test system.

Other liquid solutions are glued into the cartridge in stick packs (small aluminum bags) at predefined positions using UV adhesive. In the analysis process within an associated analyzer, in which the cartridge is subjected to various treatment cycles (spinning, temperature loading, cooling, etc.), the stick packs are caused to burst by centrifugal forces while spinning in order to initiate a chemical reaction.

Loading with lyophilizates

Another sensitive step of the process is the loading of biochemical reagents that will later react with the sample material. The environmental conditions come into play at this stage. Alongside the basic requirements of an ISO class 7 cleanroom for the production of the lab-on-a-chip test, it is also essential to control humidity and temperature when processing lyophilizates. Lyophilizates are freeze-dried substances that are specifically selected for the respective application, and must be processed in the freeze-dried state. They are extremely brittle and hygroscopic, meaning that they dissolve immediately at a humidity of more than 50 percent. The humidity inside the cleanroom cell must therefore be below 50 percent; in addition, the temperature must not exceed 25 degrees Celsius. What makes handling even more difficult is the high electrostatic charge of the lyophilizate beads, which gives them a tendency to pop out of the cartridge. This is prevented by a continuous flow of ionized air.

Sealing through thermobonding

A plastic film is applied to the disks using hot stamping to seal them. This ensures that the inside of the cartridge is atmospherically sealed. It must be ensured that this heat does not affect the reagents. In other words, the right combination of temperature, pressure, and time is crucial.

Secure primary packaging

Finally, RKT takes care of the packaging process, which is particularly demanding due to the strict hygiene requirements in cleanroom environments. The primary packaging must be airtight and effectively shield the product from contamination.
Secondary packaging can either be carried out at RKT or, alternatively, handled by the customer at their own facilities.
A double-bagging concept is also available. Using this method, components are pre-packaged in two protective layers and temporarily stored outside the cleanroom. When demand arises, they can be returned to the cleanroom without compromising cleanliness. The outer bag is removed in the airlock, allowing the inner bag to be safely opened within the cleanroom before the cartridge is loaded.

Would you like to bring your idea for a lab-on-a-chip cartridge to series production?

Stefan Preis
Head of Project Business
S.Preis@rkt.de

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