A novel vacuum-sampling method was developed to produce strip samples as thin as 2mm under conditions that simulate the solidification of the direct twin-roll casting process (CASTRIP®). This method utilizes vacuum to draw liquid steel into a copper mold chamber, promoting rapid solidification of the steel liquid into a thin strip sample. The samples exhibit uniformity, which allows for subsequent rolling processes to evaluate new strip cast alloys and products. In this paper, strip samples of high Si steel (4.5 wt.% Si - 1.5 wt.% Mn) were produced using the vacuum-sampling method. Secondary dendrite arm spacings (SDAS) were measured in the as-cast samples, which averaged 10.8μm, corresponding to solidification cooling rates of approximately 1700 K/s. The dendrite structures and calculated solidification cooling rates are similar to those observed in the commercial CASTRIP® process. Additionally, solidification cooling rates were in good agreement with cooling rates of 1680-1800 K/s obtained using MAGMA™ simulation software. Therefore, vacuum-sampling method can be used for rapid prototyping and evaluation of new alloys for the vertical twin-roll strip casting process.