Why are my microgels not centrifuging (sticking to tube)?

I have created a hydrogel water in oil emulsion using a microfluidic flow focusing device. I have been able to collect the microgels/particles from the device and then pipette/manipulate them. When I try to centrifuge them to wash them they seem to aggregate and stick to the tube walls instead of collect at the bottom of the tube. What could be causing this and how do I fix it? Below are some relevant details.


Water phase: 2 wt% Norbornene-modified hyaluronic acid, DTT (crosslinker), .1% Irgacure I2959 (photoinitiator)


Oil phase: Light mineral oil with 2% span 80 (surfactant), .1% Irgacure I2959 (photoinitiator)


[![Image of microgel aggregation/sticking](https://i.stack.imgur.com/iCUfK.jpg)](https://i.stack.imgur.com/iCUfK.jpg)


