短语讲解：

1. Traditional printers require ink to produce an image or design on a piece of paper.

a piece of 一块; 一张; 一片
例句：He nibbled a piece of bread while drawing a picture.
他一边画画儿一边啃着一片面包。

2. The bio-inks are then added to a device that researchers call the Palmetto bio-printer.

add to 增加，加强
例句：Politics will add to the policy complications.
政治也将加大政策的复杂性。

3. But they hope in a few years they may be able to print tissue to replace damaged human organs.

be able to 能，会; 能够
例句：How soon will china be able to clean up its air?
中国能在多短时间内将空气变清洁？

4. Some scientists worry about how to get blood to the replacement tissue.

worry about 担忧， 烦恼
例句：Don't worry about the results.
不要担心结果。