This paper presents a new fin pattern for liquid-cooled microchannel heat sinks. It is derived from topology optimized heat sink structures reported in our previous paper. The new fin pattern is composed of two types of fins, oblique fin and trapezoidal fin, and they are arranged in a semi-wavy manner. Numerical simulation is implemented to examine its heat transfer and fluid flow characteristics in detail. A flow phenomenon that is similar to Dean’s vortices is observed and results in enhanced flow mixing. The non-continuous fin pattern also avoids growth of thick boundary layers as they are initiated at the leading edges of each fin. Furthermore, size optimization based on the response surface method is performed to balance the heat transfer enhancement and pressure drop penalty. The new fin pattern is then compared with five other commonly used fin designs and shows the best performance in the studied flow range.