With the rapid development of laser dermatology

the epidermis cooling technology becomes more and more important

and it is of great potential for commercial application. Cryogen spray cooling (CSC) with several tens of milliseconds has been successfully applied in laser treatment of vascular diseases

which can protect epidermis from the thermal injuries due to the absorption of melanin and hence increase the incident laser energy

leading to the improvement in therapeutic outcomes. CSC involves flashing atomization and boiling heat transfer on cooling surface. The majority of previous studies were conducted experimentally. The research progresses of the mechanism of flashing atomization

spray characteristics

heat transfer dynamics and the enhancement were summarized for the past 20 years. The typical research methods and results were compared and analyzed

and the different factors to influence the heat transfer dynamics of CSC were investigated. New spray techniques

such as using lower point cryogens and hypobaric pressure method

are effective to enhance cooling capacity. Finally

the remaining difficulties in this field were clarified and the potentials of the ongoing research were pointed out.