芯 is a Japanese kanji written with 7 strokes, listed here under the keyword “wick”. It is built from 心 (heart) and 艹 (mugwort). In Remembering the Kanji by James W. Heisig it is frame 647.
On KumiJi Glyph Explorer, open the parts search and type “heart” + “mugwort”. 芯 is among the results, together with every other character containing the same shapes.
Open 芯 in the interactive kanji search
to expand every part down to its smallest pieces, add your own names and mnemonic stories,
or search for other characters by their parts.