Many of the transducers on the sensor chip require a membrane over the bare transducer so that they respond to a specific analyte. The membranes are applied to the surface of each sensor as a microscopic drop of liquid containing a few nanolitres (one billionth of a litre). The liquid then dries to leave a thin membrane over the top of the sensor. Some of the sensors require multiple membranes layers. The Sphere production facility houses a bespoke dispensing system which is used to automatically place the nano-litre volumes of liquid onto the surface of each sensor.

The membrane materials used by Sphere for the sensor array are based on those widely used for commercial blood analysers. However, the membranes have been specifically formulated and optimised for the performance characteristics required in the applications of interest.