Abstract: A composition for surface treatment includes fluorosilicic acid (H2SiF6) and hydrofluoric acid (HF), and/or a surface treatment method using the same. The composition may be used to treat (e.g., etch) a substrate such as glass or the like.

Abstract: A smart cube is disclosed. An embodiment of the present disclosure may provide a smart cube, comprising: a main frame; and a plurality of unit blocks coupled to the main frame and constituting six faces of a regular hexahedron, wherein the unit block comprises: a display unit disposed on a surface of the unit block that is exposed to an outside; and a plurality of terminals disposed on a facing surface of the unit block facing another unit block for transferring electric power and data for the display unit, wherein the terminal is retrievably disposed in an insertion hole formed on the facing surface of the unit block, and wherein the terminal includes a permanent magnet for allowing a polarity of a retrieved end of the terminal to be opposite to a polarity of a retrieved end of a terminal of the other unit block such that the terminal is retrieved from the insertion hole and adhered to the terminal of the other unit block by a magnetic force.