Rotatable cartridge for analyzing a biological sample

A method of performing a measurement of a processed biological sample using a cartridge, wherein the cartridge is operable for being spun around a rotational axis, wherein the cartridge comprises:

• a fluid chamber for receiving a fluid;
• an aliquoting chamber;
• a duct connecting the fluid chamber and the aliquoting chamber;
• a downstream fluidic element;
• a siphon for siphoning the fluid from the aliquoting chamber to the downstream fluidic element, wherein the siphon comprises a siphon entrance into the aliquoting chamber, wherein the siphon further comprises a siphon exit into the downstream fluidic element, wherein the siphon comprises a bend, wherein the bend is the portion of the siphon closest to the rotational axis, wherein the siphon entrance extends all the way from the bend to the lowest point of the aliquotinq chamber, the lowest point being located in a lower portion of the aliquoting chamber, wherein the lower portion is further from the rotational axis than the bend, wherein the aliquoting chamber has a minimum width adjacent to the siphon, wherein the siphon has a siphon width, wherein the siphon width is less than the minimum width of the aliquoting chamber in a cross-sectional view;
• and
• a fluidic structure for processing a biological sample into the processed biological sample, wherein the fluidic structure comprises the downstream fluidic element, wherein the downstream fluidic element is fluidically connected to the fluidic structure, wherein the fluidic structure comprises a measurement structure for enabling measurement of the processed biological sample, wherein the fluidic structure is configured for receiving the biological sample;
• wherein the method comprises the steps of:
• placing the biological sample into the fluidic structure;
• controlling the rotational rate of the cartridge to process the biological sample into the processed biological sample using the fluidic structure;
• filling the fluid chamber with the fluid;
• controlling the rotational rate of the cartridge to transport the fluid from the fluid chamber to the aliquoting chamber via the duct;
• controlling the rotational rate of the cartridge to fill the siphon with the fluid a first time;
• controlling the rotational rate of the cartridge to increase in order to transfer a first portion of the fluid in the siphon to the downstream fluidic element, wherein the increase in the rotational rate of the cartridge causes air to enter the siphon at the bend, wherein the increase in the rotational rate of the cartridge forces the first portion of the fluid through the siphon exit;
• controlling the rotational rate of the cartridge to fill the siphon with the fluid a second time;
• controlling the rotational rate of the cartridge to increase in order to transfer a second portion of the fluid in the siphon to the downstream fluidic element, wherein the increase in the rotational rate of the cartridge causes air to enter the siphon at the bend, wherein the increase in the rotational rate of the cartridge forces the second portion of the fluid through the siphon exit, wherein the first portion and the second portion have the same volume;
• and
• performing the measurement using the measurement structure and using a measurement system.