# A Review on Microfluidic Platforms Applied to Nerve Regeneration
## 3 Microfluidic Platforms Applied to Nerve Repair and Outgrowth
### Nerve Repair
#### 3.1.2 Microfluidic Platforms for Different Injury Models
The device uses an aspiration tube to perform vacuum aspiration at the entrance of the axonal compartment, generating an air bubble that shears the axon. The device allows damage to the axon without affecting the soma, which is not feasible in conventional non-microfluidic methods. The vacuum injury model has been applied to many studies to screen for potential drugs for axonal regeneration. [PERSON] [72] performed microarray analysis of cortical axons without somatic cell contamination. It showed a rise in cytoskeletal and intracellularly transported transcripts in vacuum. [PERSON] et al. [73] used a vacuum-based microfluidic injury device to simulate and study acute axonal degeneration verifying that calreticulin and disintegrin response mediator protein-2 can act as regulators of acute axonal degeneration in vitro. [PERSON] et al. [74] used a vacuum-assisted injury microfluidic device to study the effect of peroxisome proliferatorator-activated receptor \(\gamma\) in axon regeneration. Laser-based injury is a highly accurate and reproducible method that enables precise fine-tune of position, scale and degree of damage of the injury spot. [PERSON] [75] described a neuro-optical microfluidic platform for studying injury and subsequent regeneration of individual mammalian axons. This platform consists of three components integrated on an inverted microscope that includes a neuronal culture microfluidic device, a femtosecond laser for precise axon excision, and a microcell culture incubator for continuous long-term observation of events following injury. The degree of damage can be adjusted by tuning \begin{table}
\begin{tabular}{c c c} \hline \hline
**Research** & **Repairing Method** & **Injury Mechanism** \\ \hline [PERSON] [69] & NGF & Physical injury (compression) \\ [PERSON] [70] & NGF & Physical injury (compression) \\ [PERSON], [PERSON] [71] & Drug + NGF & Physical injury (puncture) \\ [PERSON] [72] & [PERSON] & Vacuum-assisted injury \\ [PERSON] [PERSON] [73] & NGF & Vacuum-assisted injury \\ [PERSON] [74] & Drug + NGF & Vacuum-assisted injury \\ [PERSON] [75] & Drug & Laser injury \\ [PERSON] [76] & Drug & Laser injury \\ [PERSON] [77] & Drug + neurodevelopmental genes & Laser injury \\ [PERSON] [21] & NGF & Biochemical injury \\ [PERSON] [46] & Drug + NGF & Biochemical injury \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Injury mechanisms and repair methods of different researches. the exposure time of the laser to achieve a high degree of reproducible axotomy. [PERSON] [76] used pulsed laser micro-beam irradiation and microfluidic cell culture to study the dynamics of axonal injury and regeneration in vitro. Laser pulses of 400 nJ and 800 nJ were applied to produce partial and complete transection of the axon, respectively. EGTA was used to chelate extracellular calcium and potentially reduce the severity of axonal degeneration after injury. [PERSON] [77] presented a multi-trap microfluidic device to perform neural regeneration study in _Caenorhabditis elegans_ (_C. elegans_). The device enables immobilization of 20 _C. elegans_ at the favorable orientation for precise laser surgery and optical pathway required for high-resolution imaging. Biochemical injury is a commonly used injury method to investigate neurodegeneration disease and nerve regeneration. This method can holistically affect the biological activity and survival of the neuron. In the study of [PERSON] [21], neurotoxic drugs were used to cause varying degrees of biochemical damage to neuronal axon. In the research of [PERSON] [46], biochemical injury was utilized to damage neural axons in the central compartment. This method uses concentration and duration of the neurotoxic solution to control the degree of damage. The major disadvantage of biochemical injury is the inability to cause precise damage to the axon. In addition, it needs to use large amounts of nutrient solution to flush out isolation chambers and micro-channels.