9. As shown in Figure 3, eight circles with a radius of 1 are placed inside a rectangle. Adjacent circles are tangent to each other, and the circles at the top-left and bottom-right corners are tangent to two sides of the rectangle, while the other circles are tangent to one side of the rectangle. The area of the rectangle is $\qquad$
$9.18+9 \sqrt{3}$.
As shown in Figure 9, connecting the centers of any two adjacent circles, by the properties of circles, $\triangle O_{1} O_{2} O_{3}$ is an equilateral triangle with a side length of 2, and the height of the triangle can be calculated as $\sqrt{3}$. Using the tangency of circles and lines, the lengths of the adjacent sides of the rectangle can be found to be $9,2+\sqrt{3}$. Therefore, the area of the rectangle is $18+9 \sqrt{3}$.