A dermal patch for collecting a physiological sample includes a housing with a collection chamber, a sample channel and a pin within a receptacle of the housing. The sample channel is configured to direct a physiological sample drawn from a subject to the collection chamber. The pin is removably positioned within the receptacle and is configured to move from an undeployed position to a deployed position. The pin is configured to seal the receptacle when in the undeployed position and is further configured to facilitate generation of negative pressure in the sample channel when the pin is moved from the undeployed to the deployed position.