Alexander Price, Wesley Cochrane and Brian Paegel
Department of Chemistry, The Scripps Research Institute, Jupiter FL 33458
Syringe pumps are the most popular tool for transporting fluids within microfluidic devices. In the process of loading sample into a syringe, air bubbles (derived from the syringe dead volume) frequently migrate into the barrel and require removal to achieve consistent flow. Ideally, a researcher would have a large excess of sample so that the barrel can be filled and evacuated multiple times. During loading, syringes are held vertically with the sample directly below the tip, necessitating forceful evacuation to dislodge rising bubbles, however this not feasible for low/intermediate-volume “precious” samples (50-500 µL). Here, we present a simple funnel to aid bubble removal during syringe loading.
Plastic transfer pipets (FisherBrand 13-711-7M)
Razor blade
Pipette and pipette tips
Syringe (we use Hamilton Gastight 1700 series w/ TLL tips)
1. Using the razor blade, carefully cut the end off of the transfer pipet so that it fits snugly over the tip of your syringe (Fig. 1). It might take a couple tries, but you can use this as a template once you have found the right location to cut.
2. Cut the transfer pipette again, roughly 2 inches up from the previous cut (Fig. 1). Your funnel is complete.
3. Attach the funnel onto the tip of the syringe. Holding the syringe vertically (funnel up), load your sample into the bottom of the funnel (Fig. 2).
4. Fill and evacuate the syringe barrel as needed to eliminate any air bubbles (Fig. 3).
5. Dispose of the funnel.
Figure 1. Construction of a syringe funnel from a transfer pipet.
Figure 2. The funnel is attached to the syringe (left), and sample is loaded into the bottom of the funnel (middle and right).
Figure 3. Air bubbles in the barrel are expelled into the funnel and syringe is filled.
