Abstract: An electronic device such as a wristwatch may be provided with conductive structures. The conductive structures may include a sensor electrode for an electrocardiogram (ECG) sensor. A coating may be disposed on the sensor electrode to reflect particular wavelengths of visible light so that the sensor electrode exhibits a desired color. The coating may include adhesion and transition layers on the sensor electrode, an opaque coloring layer on the adhesion and transition layers, and a thin-film interference filter on the opaque coloring layer. The thin-film interference filter may have an uppermost diamond-like carbon (DLC) layer. The DLC layer may contribute to the color response of the coating while concurrently minimizing noise in ECG waveforms gathered by the ECG sensor using the sensor electrode.

Abstract: An apparatus includes a housing having a bottom surface and one or more mounting members that enable the housing to be mounted in a rack. The apparatus includes liquid cooling components mounted within the housing. The liquid cooling components include tubing within which a coolant may be communicated, and a heat exchange component that thermally couples a heat load within the housing to the coolant so that heat from the heat load is transferred to the coolant. The bottom surface of the housing defines a drain path. The heat exchange component is positioned in a downward direction of gravity relative to the heat load when the housing is mounted in the rack. In the event of a coolant leak, the coolant leak will occur beneath the heat load and the coolant will flow away from the heat load and exit the housing by use of the drain path.