# Extending Cooling Rate Performance of Fast Scanning Chip Calorimetry by Liquid Droplet Cooling
## 5 Conclusions  
The implementation of liquid droplet cooling for fast scanning calorimetric sensors into the FSC hardware allows for enhanced cooling up to two orders of magnitude faster than with gas as the cooling medium. Significantly higher cooling rates can be achieved in the temperature region near ambient temperature. Experimental setups, combining FSC with other experimental techniques, are becoming feasible even under preferential external conditions such as room temperature and air or nitrogen as the purge gas.  
Liquid droplet cooling at 10\({}^{5}\) K/s of a polyethylene sample of 40 ng became possible with \(\mathbf{T}_{\rm t}\) at room temperature. Achieving the same speed with gas cooling requires a 1 ng sample in a liquid nitrogen-cooled He environment. Using different cooling liquids and controlling the droplet size, it was possible to roughly control the maximum cooling rate. However, boiling of coolants, which reduced the cooling rate (Leidenfrost phenomenon), limits the application of droplet cooling in FSC. Further investigations in this direction and application of other coolants are needed.  
The application of liquid droplet cooling in this work includes the vitrification of relatively large samples under conditions of limited gas temperature control, e.g., when the surrounding gas is at room temperature. The cooling rate, achieved with the droplet cooling technique at room temperature, recorded by the thermopile was ca. 50,000 K/s at the temperature of the glass transition of PBN, which is almost one order of magnitude faster than in the Mettler Toledo Flash DSC 1 with the same sensor with a cooling system and \(T_{\rm t}=180\) K (5000 K/s) and 1.5 orders of magnitude faster than the same sensor when operated at room temperature environment (3500 K/s). Gas cooling of a sensor and sample of this size is only capable of making PBN fully amorphous (cooling faster than 6000 K/s) when used with a cooler at gas temperature \(T_{\rm t}=100\) K and lower. Liquid cooling can quench large samples of PBN at rates up to 50,000 K/s at room temperature (\(T_{\rm t}=300\) K), opening opportunities for combinations with other experimental techniques, such as XRD, FTIR, POM and AFM.  
Conceptualization, C.S. and E.Z.; methodology, E.Z.; software, E.Z.; validation, R.A., C.S. and D.Z.; investigation, E.Z.; resources, D.Z.; data curation, C.S.; writing--original draft preparation, J.J.; writing--review and editing, E.Z.; visualization, J.J.; supervision, C.S.; project administration, D.Z.; funding acquisition, J.J., D.Z. and C.S. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Key R&D Program of China, grant number 2020 YFA0711504, the National Natural Science Foundation of China, grant number 21790345 and 51673094, the German Science Foundation (DFG) priority program SPP2122, grant number ZH 661/3-1. And The APC was funded by University of Rostock.  
Not applicable.  
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.  
This work was financially supported by National Key R&D Program of China (Grant No. 2020 YFA0711504), the National Natural Science Foundation of China (No. 21790345, 51673094) and the Shenzhen Science and Technology Innovation Committee (JCYJ20200109150656717 and JCYJ2017081811061313). E.Z. acknowledges financial support by the German Science Foundation (DFG) priority program SPP 2122 (Project No. ZH 661/3-1). C.S. acknowledges financial support from the Ministry of Education and Science of the Russian Federation (Grant No. 14.Y26.31.0019).  
The authors declare no conflict of interest.