The silicon hairspring is not an incremental improvement: it's a paradigm shift in regulating watch movements. The traditional component — a steel strip coiled around the balance staff — works well, but suffers from three historical enemies: magnetism, temperature variations, and the need for lubrication. Silicon eliminates all three at once.
The material is produced through photolithography, the same technology used in semiconductors. It's not forged, not drawn: it's etched. This allows geometries impossible with metals, including the terminal curve integrated in the same plane as the hairspring — a solution that improves isochronism without soldering or adding mass. The original patent, filed in the early 2000s by a consortium including Rolex, Patek Philippe and the Swiss CSEM, has now expired, and today the silicon hairspring is adopted by Tudor in calibers MT5201, MT5412 and MT5633, by Tissot in the Powermatic 80 Si, by Rolex in caliber 7140 with its proprietary Syloxi variant, by Glashütte Original in calibers from the 36 series, and by many ETA movements and derivatives including the STP 1-21, COSC certified.
On the bench, the difference compared to steel is immediately measurable: there's no oil to apply to the hairspring, eliminating a source of long-term drift. The steel hairspring, as it ages, absorbs or loses lubricant and changes behavior; the silicon one doesn't. Thermal stability is guaranteed by an almost negligible expansion coefficient within the operating temperature range. Anti-magnetism is intrinsic: silicon is paramagnetic by nature, not by surface treatment.
Limitations exist. Silicon is fragile — a sharp impact on the crystal edge during servicing can break the hairspring, while steel will deform and sometimes recover. Production costs remain high for small batches, and not all traditional hairspring manufacturers have invested in the necessary equipment. Alloys like Nivachron or Anachron remain competitive on medium-high volumes. But where high anti-magnetic certification is required — 15,000 A/m and above — the silicon hairspring is today the most direct solution.