PLT bioreactor design. (A) PLT bioreactors are based on custom-built polydimethylsiloxane (silicon-based organic polymer) bonded to glass slides, and are comprised of an upper and lower microfluidic channel separated by a series of columns. (B) The 2 µm gaps separate columns to trap MKs entering the upper channel from crossing into the lower channel upon fluid withdrawal from the outlet of the lower channel. (C) Scanning electron micrograph of bioreactor central channels. (D) Scaled bioreactor design showing typical device operation. Scale bars represent 50 µm (B) and 5 µm (C).