One of the main advantages of spatial segregation of axons is the possibility to investigate specific mechanisms of CNS axonal injury and degeneration, as well as possible regeneration [41]. Since axonal injury and degeneration are closely associated with pathophysiology of traumatic brain injury and many neurodegenerative diseases, a number of approaches have been developed to study axonal injury in vitro. Initial attempts to perform axotomy used mechanical cut [42], but the lack of reproducibility and poor spatial control underlined the need of new techniques. Microfluidic axon isolation devices allowed better control on axonal growth and injury (using vacuum aspiration or mechanical transection of axons) [5,26]. Microfluidic devices have been used in combination with many types of experimental axonal injuries. Focal laser irradiation, using either femtosecond laser [43] or less harmful pico- and nanosecond laser [44], allows precise and localized axonal damage. In three-compartmental microfluidic devices, which have a cleft in between the somatic and the distal axonal chambers, injury has been performed by flux of detergent [45] and by valve-based micro-compression [46]. Other multi-compartment chips, designed to study axon-glia interaction [29], provide information on migration and functional interaction of glial cells with damaged axons after injury [47,48].
