Question 1

How does the delivery of a compound remain localized and does not diffuse to other areas?

Celine Billerit · Accepted Answer

The BioPen tip has 3 channels at its front, introduced into the open volume:

The central channel serves as an injection port or output channel (positive pressure), where liquid is delivered to the open volume.
Two adjacent channels function as aspiration ports or input channels (negative pressure), through which liquid is drawn in from the sample dish (see figure below).

Perfusion recirculation — *Schematic of the hydrodynamic flow formed at the end of the pipette tip*

Balancing this inflow and outflow, creates a small perfusion volume or delivery zone at the front of the BioPen tip.

To generate a localized delivery zone, the flow rate of the aspiration port has to be higher than the flow rate of the injection port, such that all fluid leaving the outlet would flow entirely into the neighboring inlet. Flow recirculation provides a mean to maintain a localized delivery volume, which would otherwise rapidly fade by diffusion and contaminate the surroundings.

Standard flow conditions are set to have 10 times more inflow than outflow.

Question 2

How does the delivery of a compound remain localized and does not diffuse to other areas?

Celine Billerit · Accepted Answer

The BioPen tip has 3 channels at its front, introduced into the open volume:

The central channel serves as an injection port or output channel (positive pressure), where liquid is delivered to the open volume.
Two adjacent channels function as aspiration ports or input channels (negative pressure), through which liquid is drawn in from the sample dish (see figure below).

Balancing this inflow and outflow, creates a small perfusion volume or delivery zone at the front of the BioPen tip.

To generate a localized delivery zone, the flow rate of the aspiration port has to be higher than the flow rate of the injection port, such that all fluid leaving the outlet would flow entirely into the neighboring inlet. Flow recirculation provides a mean to maintain a localized delivery volume, which would otherwise rapidly fade by diffusion and contaminate the surroundings.

Standard flow conditions are set to have 10 times more inflow than outflow.