A device for withdrawing a fluid, preferably blood or interstitial fluid, from the skin and/or from beneath the skin of a subject, the device comprising: a reversibly deformable structure, wherein the reversibly deformable structure is switchable from a first stable configuration, through an unstable configuration, to a second stable configuration; an actuator that, when activated, switches the reversibly deformable structure from the first stable configuration to the second stable configuration; a fluid transporter fastened to a deformable portion of the deformable structure, wherein the fluid transporter comprises one or more microneedles, wherein in the first stable configuration of the reversibly deformable structure, the one or more microneedles are not contactable with the skin of the subject and in the second stable configuration, the one or more microneedles are insertable into the skin of the subject; a separate retraction mechanism able to move the fluid transporter away from the skin after the reversibly deformable structure reaches the second configuration; a pressure regulator comprising a pre-packaged vacuum chamber having an internal pressure less than atmospheric pressure prior to the point at which the device is used; and a storage chamber separate from the vacuum chamber for receiving the fluid withdrawn from the subject; and an activator and a seal that, when activated, the activator punctures the seal to fluidly communicate the vacuum chamber and the storage chamber with the one or more microneedles; wherein, when the device is applied to the surface of the skin of a subject and the structure is deformed by the actuator to switch the structure from the first stable configuration to the second stable configuration, the fluid transporter is driven into the skin of the subject. a reversibly deformable structure, wherein the reversibly deformable structure is switchable from a first stable configuration, through an unstable configuration, to a second stable configuration; an actuator that, when activated, switches the reversibly deformable structure from the first stable configuration to the second stable configuration; a fluid transporter fastened to a deformable portion of the deformable structure, wherein the fluid transporter comprises one or more microneedles, wherein in the first stable configuration of the reversibly deformable structure, the one or more microneedles are not contactable with the skin of the subject and in the second stable configuration, the one or more microneedles are insertable into the skin of the subject; a separate retraction mechanism able to move the fluid transporter away from the skin after the reversibly deformable structure reaches the second configuration; a pressure regulator comprising a pre-packaged vacuum chamber having an internal pressure less than atmospheric pressure prior to the point at which the device is used; and a storage chamber separate from the vacuum chamber for receiving the fluid withdrawn from the subject; and an activator and a seal that, when activated, the activator punctures the seal to fluidly communicate the vacuum chamber and the storage chamber with the one or more microneedles; wherein, when the device is applied to the surface of the skin of a subject and the structure is deformed by the actuator to switch the structure from the first stable configuration to the second stable configuration, the fluid transporter is driven into the skin of the subject.