Hand-held syringe as a portable plastic pump for on-chip continuous-flow PCR: miniaturization of sample injection device†
Abstract
On-chip continuous-flow polymerase chain reactions (PCRs) generally require peripheral apparatus such as a pump for injecting a sample liquid into the fluidic channel. This makes the overall instrumentation bulky, limiting integration. In this study, we propose a new scheme for injecting a sample employing a hand-held syringe as a portable plastic pump, and apply it to an on-chip continuous-flow PCR. In the proposed injection scheme, sample actuation was realized inside a highly gas-permeable and blunt-ended fluidic conduit connected to a hand-held plastic syringe filled with compressed air. In this system, the degree of air diffusion via the walls of the gas-permeable conduit becomes greater in the anterior (closer to the outlet) end of the sample plug than the posterior (closer to the inlet) end, because a relatively larger quantity of air is retained inside the syringe at the posterior end of the sample plug. This creates a pressure gradient at the inlet and outlet of the fluidic conduit and propels the sample forward toward the outlet. Preliminary experiments were performed for the quantitative analyses and evaluation of the proposed sample injection scheme using gas-permeable