The present invention generally relates to systems and methods for delivering and/or withdrawing fluid from subjects, e.g., through the skin, including packaging associated with such systems. Certain aspects of the invention are generally directed to devices for withdrawing a substance from the skin and/or from beneath the skin of a subject, and/or for delivering a substance to the skin and/or to a location beneath the skin of a subject. In some embodiments, the devices may comprise one or more skin insertion objects, such as needles or microneedles. In some cases, the device also may comprise one or more vacuum chambers, e.g., having an internal pressure less than atmospheric pressure. In some aspects, the device may be contained within an environment able to assist with maintenance of such pressures. For example, a package containing such an environment may also have a pressure less than atmospheric pressure, and/or the package may be molded to the device or otherwise have a shape that does not contain substantial gases that can “leak” into the device and alter the pressure of any vacuum chambers that may be contained therein. In some embodiments, the pressure of the environment may be the same as or less than that of vacuum chambers contained within the device. Other aspects of the invention are generally directed to methods of creating such devices, techniques for using such devices, kits involving such devices, and the like.
