Among others, the present invention provides apparatus comprising two micro-devices each fabricated by the method comprising: the first step of depositing a first material onto a substrate； the second step of depositing a second material onto the first material and then patterning the second material with a microelectronic technology or process； and repeating the second step at least once with a material that can be the same as or different from the first or second material. The micro-devices can pierce through the membrane of a circulating tumor cell and can move in different direction.
