Using the experience gained from the PCR test cartridge project for rapid MRSA and SARS-CoV-2 tests, RKT oversaw the volume production of a lab-on-a-chip disk used for the detection of skin psoriasis and also distinguished it from eczema. Throughout the development phase, we worked closely with the Hahn-Schickard-Gesellschaft research institute that directed the pre-series production runs of the start-up. In the following case study, we describe the project, detailing which production steps were carried out by RKT.
Mini Lab Disk for Skin Diseases
The single-use cartridge contains all the reagents required for PCR-based detection of the skin disease psoriasis. Image: ©Dermagnostix GmbH
Dermagnostix, a spin-off of the Hahn-Schickard-Gesellschaft, has leveraged extensive research in centrifugal microfluidics to develop a robust toolbox for liquid interconnections in lab-on-chip test systems. This innovation provides a scaled-down version of traditional laboratory procedures, offering enhanced efficiency and precision in diagnostic testing.
Product Development at the Client
The project’s goal was to integrate a biochemical assay into a PCR detection method suitable for dermatological diseases on a lab-on-a-chip cartridge. Precisely defining the intended use was crucial to specify the product’s functionality, application environment, and operational requirements and Hahn-Schickard successfully integrated the assay into a centrifugal CD-shaped system. Dermagnostix emerged as a spin-off to commercialize the concept into a viable product for the medical market. RKT collaborated closely with Hahn-Schickard and Dermagnostix in engineering initial prototypes, refining design elements, and optimizing fluidic specifications to ensure the system’s effectiveness and reliability.
Plastic-Compatible Design by RKT
RKT closely specified the design specifications for the plastic material and supervised the development of the steel injection molding tools. Demolding the components from the mold smoothly was critical, requiring the careful implementation of demolding chamfers and radii. Subsequent rigorous testing verified the functionality of the resulting fluidic components.
Semi-Automated Assembly Process
The disk was made of two injection-molded plastic components: a substrate and cover made to exact specifications. They were assembled using multiple stations. After injection molding, the substrate, containing fluidic channels, chambers, and necessary reagents was assembled. A sealing film was then applied to the substrate using a thermobonding process, sealing the disk and its biochemical contents securely.
Hahn-Schickard managed the pre-series and small-scale production phases. As demand escalated, exceeding 90,000 cartridges, production transitioned to RKT’s semi-automated assembly line. RKT meticulously developed assembly procedures encompassing assembly, sealing, primary, and secondary packaging of the cartridges in close collaboration with Hahn-Schickard.
Coating and Pipetting
Initially, a hydrophobic coating was applied to ensure smooth transport of the medium through the chambers during analysis. This critical step was carried out using a dosing robot known for its precision and repeatability and enabled the transition from prototyping and small series production at Hahn-Schickard to large-scale production at RKT.
In the same station, another complex task was accomplished: accurately pipetting four different primer solutions, each with a volume of only 5 microliters. Precision in dosing was critical to avoid any issues within the fluidic system.
Equipping Disks with Stick Packs and Lyophilizates
A subsequent semi-automated station was used to load stick packs containing solutions of various ingredients. The packs had to be precisely positioned and secured onto the substrate using UV adhesive. Fragiel Lyophilizates (freeze-dried reagents) were introduced into the assembly in the next station.
Sealing Station with Thermobonding
Next, the disk was sealed with a sealing film utilizing a precise thermobonding process. Careful development and control of temperature, pressure, and time were required to ensure optimal bonding between the substrate and the film based on the compatibility of the plastic chemistries.
At the final assembly station, the cover and a cover label were attached to the substrate, and the completed assembly was carefully packaged in an airtight aluminum bag.
Extensive Quality Assurance Efforts
Strict adherence to client specifications was critical for process development and scaling. We needed to maintain dimensions of less than 100 µm with a maximum allowable error of 10%, across all stages of production. Throughout the project, our efforts focused on quality assurance of the disk components, which included meticulous measurement of steel parts for precision mold construction and validation of the injection molding process through Design of Experiments (DOE). Quality control included a 100% inspection process initially performed manually during ramp-up, later transitioning to automated vision inspection utilizing cameras.
Effective team communication was crucial to ensure continuous coordination for client validations and approvals throughout the project.
View of the ISO7 clean room at RKT: The final quality check, carried out manually during initial production, was fully automated using a camera vision systems for full production. Stick packs are processed with the UV light workbench on the right.
Less Effort and Investment
Involving RKT early in the product design process allows us to integrate our plastics expertise from the very beginning which can save our customers’ effort, time, and costs. Early collaboration provides access to our full value chain capabilities.