Devices for collecting biological samples

A handheld device for collecting a blood sample from a subject, the handheld device comprising:

• a housing comprising a base surface configured to be placed onto a skin of the subject;
• an interface on the housing, wherein the interface is configured to be moved in a first direction in order to activate one or more piercing elements that are extendable through an opening of the housing in a second direction to penetrate the skin of the subject to enable collection of the blood sample into a cartridge coupled to the housing while the skin is drawn into a recess located on the base surface of the housing, the first direction being different from the second direction;
• a vacuum chamber in the housing;
• and
• another interface on the housing, wherein the another interface is configured to activate the vacuum chamber and cause the skin to be drawn into the recess of the housing, wherein the interface is configured to be initially in a locked state that prevents activation of the one or more piercing elements prior to activation of the vacuum chamber by the another interface,
• wherein the housing further comprises a window that permits observation of a progress of a collection of the blood sample as the blood sample flows into and is collected in the cartridge.