THERE are more than a dozen sorts of three-dimensional (3D) printer. They all build up objects, layer by layer, but what the layers are made of varies from one to another. Some extrude filaments of molten plastic. Some spray special “inks”, such as liquid polymers that solidify when exposed to ultraviolet light. Some use powdered plastic or powdered metal that is then fixed in place with a laser or an electron beam. Now there is yet another way. Staples, an office-supplies company, has introduced it at its store in Almere in the Netherlands. And the layers their machine prints are made of a substance that Staples has in abundance: A4 sheets of paper.

三维（3D）打印机有十来种类型。所有的3D打印机都是将东西一层一层地打出来，但是所用的打印方式却各不相同。有的是挤出熔融的塑料丝；有的是喷出特殊“墨水”，如受到紫外线照射时会固化的液态聚合物；有的采用塑料或金属粉末，通过激光或电子束将其固定到指定位。现在又出现了另一种打印方式。史泰博这一办公用品公司在其位于荷兰阿尔梅勒的商店中引入了采用这一方式的设备。而该设备打印所用的材料对史泰博来说可谓资源充足：A4纸。