1. **State the problem:** Simplify the expression $2\sqrt{-16}$.\n\n2. **Recall the formula and rules:** The square root of a negative number involves imaginary numbers. Specifically, $\sqrt{-a} = \sqrt{a}i$ where $i = \sqrt{-1}$.\n\n3. **Apply the rule:** $\sqrt{-16} = \sqrt{16}i$.\n\n4. **Calculate the square root of 16:** $\sqrt{16} = 4$.\n\n5. **Substitute back:** $\sqrt{-16} = 4i$.\n\n6. **Multiply by 2:** $2 \times 4i = 8i$.\n\n**Final answer:** $8i$