What is the smallest volume I can use and still get a good foam?

The smallest volume to foam up properly is 4-5 µl but the  small volume is not easy to handle. For 4-5 µl silk, you can add maximal 1 µl cells to the silk. Cell suspension volume radio to silk should exceed 0.25, or the silk will get too diluted and hard to stabilize.

For scale-up, the foam can be cut into smaller pieces of the desired size after the cells have been amplified.