A copolymer is provided which is capable of providing an article surface with sufficient oil repellency against oils having low surface tensions and which places little burden on the environment. An exemplary housing of an automatic injection device may be overmolded with one or more gripping surfaces to facilitate gripping and manipulation of the automatic injection device by a user when performing an injection. The invention provides a means to stop blood flow to the heart for a relatively long period of time, thereby allowing the performance of certain procedures that require coronary artery blockade. The first exhaust chamber is disposed so as to face the positive electrode terminal of the first unit cell, and discharges a gas which is emitted from the positive electrode terminal of the first unit cell.