This disclosure describes microfluidic tissue biopsy and immune response drug evaluation devices and systems. A microfluidic device can include an inlet channel having a first end configured to receive a fluid sample optionally containing a tissue sample. The microfluidic device can also include a tissue trapping region at the second end of the inlet channel downstream from the first end. The tissue trapping region can include one or more tissue traps configured to catch a tissue sample flowing through the inlet channel such that the fluid sample contacts the tissue trap. The microfluidic device can also include one or more channels providing an outlet.