UDI - an opportunity for process optimization

Is this the right heart valve? How old are the surgical instruments? UDI marking will answer this question in the future. It challenges manufacturers in new ways, but also provides an opportunity to completely restructure processes and increase efficiency

Unique product identification is required in almost every industry. Manufacturers and consumers want maximum transparency and traceability. For medical devices, the European Union is currently introducing UDI marking (UDI = Unique Device Identification). The system has been agreed and recognized with the USA by the International Medical Device Regulators Forum (IMDRF).

UDI is intended to provide information about the origin and properties of a medical device over its entire lifetime. Medical devices sold in the EU are to be clearly identifiable by the end of December 2028 in accordance with EU Regulation 2017/745. The deadlines in the Medical Device Regulation (MDR) are based on whether medical devices are classified as high, medium or low risk. Those with high risk (e.g. artificial joints or heart valves) have to be labeled since May 2021, in vitro diagnostic devices since May 2022. For the other classes, the deadlines have been extended. Depending on the product type, medical devices with medium risk (e.g., anesthesia instruments or hearing aids) and low risk (e.g., walking aids and bandaging material) must be UDI-marked from the end of December 2027 and the end of December 2028, respectively.

The goal is greater patient safety. Still, UDI involves a lot of effort and is a challenge for manufacturers with a broad portfolio. However, the extension of the deadline offers the opportunity to go beyond the simple fulfillment of regulatory requirements and to optimize logistics and sales processes in the course of the changeovers, thereby enhancing the quality, safety and efficiency of the entire product range.

DI+PI = UDI

The UDI is composed of the Device Identifier (DI) in the front part and the Production Identifier (PI) in the back part. As a globally unique article number, DI describes the static properties: product, manufacturer, risk class. It is defined by four allocation offices accredited by the EU Commission: GS1, HIBCC, ICCBA and IFA.

PI describes the variable data of the medical device for individual identification: date of manufacture or expiry, lot or batch number, serial number, etc. In the central database Eudamed (European Databank on Medical Devices), which is currently being set up, each manufacturer must register each medical device with its UDI before importers or distributors as well as pharmacies, clinics or practices check and add to the data. In this way, Eudamed is expected to document the characteristics of each product. The counterpart to the Eudamed database in the U.S. is the GUDID (Global Unique Device Identification Database), database of the U.S. Department of Health and Human Services.

For this, manufacturers are required to mark each medical device or its packaging and container packages with UDI - well-positioned and at least in duplicate: as plain text and machine-readable 1D bar code or 2D Data Matrix code. This can be done by ink, laser or label. If there is not enough space, the plain text can be omitted.

Crucial point: the choice of printing technology

A wide range of medical device materials and packaging are a challenge for the marking. To ensure that the UDI remains reliable and permanently legible, the choice of printing technology is significant.

Laser marking is primarily well suited for direct marking of plastic or metal, and also achieve very good results on paper folding cartons. Using a powerful laser, a color change is caused in the material itself, from light to dark or vice versa (color change), or printed ink is removed to expose the substrate behind it (ablation).

To achieve a positive result, the following parameters have to be coordinated with each other: Pulse duration, pulse spacing and possibly modulation of the laser beam; wavelength; focusing of the laser beam; speed of the production line. The material has a very strong influence as well. Paper types with a specific surface finish (kaolin or calcium carbonate) can affect marking performance. For plain paper grades with calcium carbonate as filler, CO2 lasers with wavelengths around 10.6 µm work less well, while 9.3 µm gives significantly better results with both fillers. The REA JET CL - CO2 laser system - marks folding cartons permanently and with high precision, while metals such as stainless steel and titanium, plastics and thin foils are marked by the fiber laser system REA JET FL.

Inkjet printers are often integrated into the production line for serializing packaging. In all processes, the print heads stay at a distance from the material, while thermal or thermal transfer print heads are always in direct contact with the material.

Thermal inkjet printing processes have a heater in the nozzle that creates a vapor bubble that ejects the ink droplet. The process is therefore called "Thermal Inkjet" (TIJ). Cartridges with integrated print heads from Hewlett Packard are frequently used in industry. These print up to 700 meters/minute, typical speeds are around 100 to 200 meters/minute.

These systems are preferred for marking absorbent materials with water-based inks, such as folding cartons that are unvarnished at the marking position. The ongoing development of solvent-based inks has significantly expanded TIJ's field of application: For example, non-absorbent materials (foils or metal) can now also be marked with them. Disadvantages are the low print height of only 12.7 millimeters and the small distance between the print head and the marking surface.

Advantages of the TIJ are the high resolution and print quality. The REA JET HR 2.0 inkjet printers, for example, print at up to 600 dpi vertically and 1,500 dpi horizontally at product speeds of up to 762 meters/minute on absorbent and non-absorbent surfaces. The combination of two printheads enables print heights of up to 25.4 millimeters. The new wet-on-wet printing process - creation and immediate marking of a color mirror - marks non-absorbent dark or transparent surfaces (foils, plastic and metal) with high contrast and good legibility.

TIJ is also suitable for Tyvek. The material, made of plastic fibers, allows hot steam to pass through so that packaged medical devices can be sterilized. Since fiber structure and permeability cause ink to run unevenly, it must dry quickly and adhere well.

Piezo inkjet printing works with a piezo crystal in the nozzle. This changes shape at lightning speed under electrical voltage and ejects ink droplets onto the print surface. In industry, these print heads were often found that work with oily inks and deliver low-resolution print images of about 100 dpi and heights of up to 100 mm. This technology is less suitable for serializing small folding boxes, but it is suitable for marking transport boxes. Newer developments such as the REA JET UP provide shipping units with content that previously had to be printed on labels, and does so with high print quality and edge definition. Its new patented and fast-drying ink formulation also enables high-resolution direct printing on surfaces of lacquered cartons.

Where direct marking is not possible or not wanted, labels are used. They are usually produced using thermal transfer printing, in which the heating element in the print head transfers the ink from the ribbon to the label. Depending on the choice of label and printing ribbon, the printed images can be of high quality and durability. REA LABEL systems offer two options for labeling shipping units of all sizes in different locations: They apply pre-printed labels or print, dispense and apply labels as complete print-and-apply systems.

Keep the code quality control in mind

Defective, recalled or expired medical devices can only be quickly identified with proper and legible UDI. So manufacturers should ensure that the marking is correct and error-free, its content is accurate, and its quality meets international standards. This is not done by handheld scanners, which are significantly more error-tolerant than fixed-mount scanners.

The basis for checking UDI code markings are both standards ISO/IEC 15415 and ISO/IEC 29158. The most important test parameters include: Symbol contrast - maximum difference between dark elements and light elements of the code or substrate; Modulation - consistency of reflections in the light and dark module areas of the 2D code; fixed pattern damage - examination of quiet zones in the 2D code which are without user data but provide position recognition and serve as an auxiliary factor; Code size (module size) - "passed" for sufficient size or "failed". Special code inspection systems such as those from REA VERIFIER help manufacturers with the measurement-based, qualitative assessment of their UDI markings - stationary, mobile or integrated into production.