Another online retailer is going bricks-and-mortar in Chicago. Boll & Branch, a 10-year-old purveyor of organic cotton sheets that built its mom-and-pop business with homespun radio commercials and a direct-to-consumer sales model, is opening up a very small store Tuesday in Oakbrook Center, offering customers an actual display bed to see and feel the previously virtual offerings in person. “Chicago made a ton of sense for us, because we have pretty high levels of awareness in Chicago already,” said Katia Unlu, 36, Boll & Branch’s chief commercial officer.