Every time you touch your smartphone screen, your finger glides over indium. A thin layer of indium tin oxide (ITO) makes glass simultaneously transparent and electrically conductive. Without it, no touchscreen, tablet, or OLED TV would work.
Indium is a remarkably soft metal — you can scratch it with a fingernail. When bent, it produces a distinctive squeak called the 'indium cry,' caused by crystal planes sliding over each other. It was named after the color indigo: spectral analysis reveals bright blue emission lines.
Indium is a critically important raw material for modern electronics. The world consumes over 1,200 tons of indium each year, mostly for ITO coatings. Known reserves stand at only about 16,000 tons. Researchers are actively seeking alternatives: graphene, silver nanowires.
Beyond screens, indium is needed for blue and white LEDs (the InGaN alloy) and CIGS thin-film solar panels. It's also essential in cryogenics: indium gaskets work at temperatures where rubber becomes brittle.
Metallic indium has low toxicity and is safe to handle. However, inhaling indium dust and its compounds can cause pulmonary fibrosis — a serious occupational disease among semiconductor industry workers. The condition develops slowly, over years. When machining indium, a respirator and exhaust ventilation are mandatory.
Indium was named after the color indigo — its spectral lines are a vivid blue. The discoverers spotted them while analyzing zinc ore.
Every smartphone holds 20–30 mg of indium in its ITO coating. Billions of screens per year add up to thousands of tons of a rare metal.
When you bend indium, it lets out a 'cry' — a distinctive squeak caused by crystal lattice planes sliding past each other.
Indium stays soft even at −200°C — most metals become brittle at such temperatures.
Indium is so soft (1.2 on the Mohs scale) that you can scratch it with a fingernail. Only cesium, gallium, and a few alkali metals are softer.
| Isotope | Mass (u) | Abundance | Half-life | Decay |
|---|---|---|---|---|
113In | 112.904058 | 4.29% | stable | — |
115In☢ | 114.903878 | 95.71% | 4.41×10¹⁴ years | β− |
Spectroscopic analysis of zinc ore