Laser Marking vs Etching on Surgical Instruments: UDI Guide

Since the EU Medical Device Regulation and the FDA’s UDI rule came into force, a surgical instrument is no longer just a tool — it is a data record that has to survive its own working life. Every reusable Class I, II and III device must carry a permanent, machine-readable Unique Device Identifier directly on the instrument, because the instrument spends most of its existence separated from any label or packaging. The question every manufacturer had to answer was simple: how do you write a code onto hardened steel that stays legible through a thousand autoclave cycles? The two contenders are laser marking and acid etching, and they are not equal.

Why the mark has to be permanent

A UDI carries two parts: a device identifier that names the model and manufacturer, and a production identifier covering lot, serial and dates. Encoded into a 2D Data Matrix (ECC200) code a few millimetres square, it must remain scannable after repeated cleaning, ultrasonic baths, steam sterilisation at 134°C, and years of handling. Ink, adhesive labels and pad printing fail this test outright — they wear or dissolve. That leaves two methods that alter the metal itself.

Acid etching: the traditional method

Chemical etching, often applied through an electrolytic stencil, uses acid to eat a shallow recess into the steel in the shape of the mark. It is fast, inexpensive and needs modest equipment, which is why it dominated instrument marking for decades and still marks plenty of older trays.

Its weaknesses are exactly where modern traceability is demanding. An etched mark is a physical cavity — a recess with edges and a floor — and that cavity is a place for bioburden, cleaning residue and moisture to lodge. Under repeated sterilisation, an aggressive etch can also become a corrosion initiation site if the passive layer around it is disturbed. And etching is comparatively shallow, so a deep-enough-to-last mark and a shallow-enough-to-stay-clean mark pull in opposite directions.

Laser marking: how it became the standard

Laser marking on surgical steel is usually done by annealing, not engraving. A pulsed fibre laser — typically a MOPA-type source that allows fine control of pulse duration — heats the steel locally without vaporising it. That controlled heat grows a dark, oxide-rich layer just beneath the surface. The result is a high-contrast black mark that is flush with the surrounding metal: no recess, no raised burr, no material removed.

That flatness is the whole point. Because laser annealing does not gouge the surface, it leaves no crevice to trap bioburden and — done correctly — preserves the passivation the corrosion-resistant surface depends on. The mark is part of the oxide chemistry of the steel, so it cannot flake or wear off without removing the metal beneath it. It survives autoclaving indefinitely.

Laser systems also mark titanium beautifully, producing legible codes on the small, curved surfaces of implants and micro-instruments where mechanical or chemical methods struggle. And because the beam is software-driven, each instrument can carry a unique serial number with no tooling change — essential for serialised UDI.

Head-to-head comparison

What this means for a buyer

If you are procuring instruments that must carry UDI and endure reprocessing — which today is essentially all reusable surgical instruments — laser annealing is the method to specify. It satisfies the regulator’s demand for a permanent, machine-readable mark while satisfying the CSSD’s demand for a surface that cleans easily and does not corrode.

Etching still has a place for internal asset tags, non-critical identifiers, or legacy instruments where full UDI compliance is not in scope. But for anything that has to reconcile traceability with sterility, the recessed cavity of an etch is a liability the flat laser mark avoids.

When you review a supplier, ask three things: is the UDI applied by laser annealing; is the code a scannable 2D Data Matrix; and is the marking validated so it does not compromise corrosion resistance. A manufacturer working under ISO 13485 and CE conformity should be able to answer all three without hesitation. The same laser step sits near the end of the instrument manufacturing sequence, right before final inspection and release.

How the mark is read once it reaches the hospital

A permanent mark is only useful if the hospital’s systems can read it, and that depends on how the data is encoded, not just how it is applied. UDI codes are issued under an accredited agency — most commonly GS1, with HIBCC and ICCBBA also recognised — and each defines the syntax packed into the Data Matrix. The device identifier stays fixed for a model; the production identifiers (lot, serial, manufacturing and expiry dates) vary per batch or per instrument.

In central sterile, a fixed-mount or handheld 2D scanner reads the square Data Matrix as an instrument is checked in, assembled into a set, and released. Because a laser-annealed code sits flush and high-contrast, it scans reliably even after the surface has dulled slightly with age — one more reason the flat mark outperforms a shadow-filled etched recess, which can misread once residue or corrosion builds in the cavity.

This is what closes the traceability loop: a specific instrument can be tied to the tray it belonged to, the cycle that sterilised it, and ultimately the procedure it was used in. If a recall or an infection investigation arises, that chain is only as trustworthy as the mark’s legibility years down the line. Specifying laser marking is therefore not a manufacturing preference — it is what makes the hospital’s own tracking systems dependable over the instrument’s full service life.

Written by Ali, Fizza Surgical instrument engineering team — Sialkot, Pakistan. ISO 13485 certified and CE marked, with four decades in instrument manufacture.