Why Pacemakers Use Laser-Welded Titanium and Ruby-Glass

Cardiac pacemakers rely on laser-welded titanium enclosures and ruby-glass feedthroughs to ensure the survival of ultra-low-power electronics inside the harsh environment of the human body. This specialized combination creates a hermetic—or completely airtight and watertight—seal that blocks corrosive bodily fluids and moisture vapor from destroying delicate circuitry. By combining biocompatible titanium, precision laser welding, and electrically insulating ruby-glass seals, engineers can guarantee that a pacemaker functions reliably for a decade or more without poisoning the patient or suffering catastrophic electrical short circuits.

The human body is an exceptionally hostile environment for electronics. Internally, a pacemaker is constantly submerged in warm, salty bodily fluids that act as a corrosive electrolyte. At the same time, the body's immune system actively attacks and attempts to reject foreign materials. If even a microscopic amount of moisture penetrates the pacemaker's housing, it will corrode the microchips, drain the battery, and cause the device to fail, putting the patient's life at risk.

Titanium is the ideal material for the outer casing because it meets two critical requirements: biocompatibility and durability. The human immune system does not recognize titanium as a threat, meaning the body will not reject the implant or cause severe inflammation around it. Furthermore, titanium is completely impervious to corrosion from salty bodily fluids, while remaining lightweight and strong enough to protect the internal components from physical impacts.

To lock the electronics inside the titanium shell, manufacturers use laser welding to create a hermetic enclosure. Traditional sealing methods, like adhesives or rubber gaskets, degrade over time and eventually allow water vapor to seep inside. Soldering uses toxic metals that cannot be placed inside the body, and conventional welding generates extreme heat that would instantly fry the sensitive electronics and lithium battery inside the casing. Laser welding solves this by focusing a microscopic, high-energy beam directly onto the seam of the titanium halves. It melts and fuses the metal instantaneously creates a permanent, molecular-level seal while keeping the surrounding casing and internal electronics completely cool.

While a completely sealed metal box protects the electronics, it creates a new problem: the electrical pacing pulses must get out of the box to reach the heart muscle. Passing a metal wire directly through a hole in the titanium case would cause two failures. First, it would break the hermetic seal, letting moisture in. Second, because titanium is conductive, the wire would short-circuit against the metal casing, draining the battery and stopping the pacing signal from reaching the heart.

Engineers solve this using a component called a hermetic feedthrough, which utilizes ruby or specialized glass-ceramics. A tiny opening is made in the titanium, and a biocompatible platinum-iridium wire is suspended in the center of the hole. The gap between the wire and the titanium wall is filled with molten glass or fitted with a synthetic ruby insulator that is brazed into place with gold.

Ruby and glass are electrical insulators, meaning they completely isolate the conductive wire from the conductive titanium case. Because pacemakers use ultra-low-power electronics to make a tiny battery last up to 15 years, they operate on micro-amperes of current. Any electrical leakage would ruin the device's efficiency. Ruby and glass prevent even the slightest current from leaking into the case. Additionally, these materials can be bonded directly to metal at a molecular level, maintaining the absolute hermetic seal required to keep microscopic water vapor out of the enclosure for the lifespan of the patient.