Took my ink pens out the other day and every one of them was clogged up.
I notice the price of ultra sonic cleaners ran from 20 to 400 bucks. One of the reviews on a 20 dollar cleaner, the guy opened it up and there was a small motor taped inside of it. So put my pens in a jar of windex, capped it and then taped the jar to the top of my dehumidifier. That thing vibrates like crazy. To my surprise 6 of the 8 pens now worked, and the other 2 i replaced the windex and put them back in the jar for more cleaning.