A method and a device for determining liver function are described. The polymers and compounds according to the invention can have excellent solubility in organic solvents and excellent film-forming properties. The apparatus comprises a user device interface configured to communicate with user device applications and a permissions module configured to define user access permissions, including temporary user access permissions, relating to individual ones of the one or more items of content. The top seal has a slight gap from the motor shaft to form a throttle structure which increases a flow resistance.