This comes up too often on the forum to not have one single post that can be pointed to for every "Can I haz OP-1 to MIDI pleez?" post. (Just kidding, this is obviously something not understood very well by the general music-making population)
In order to connect your OP-1 to another MIDI device, you will need a device that acts as a USB Host. This is because USB is not just some electrical signals, but is a data protocol. That means when you hook up your computer mouse to your laptop, the computer acts as a host to say "what are you, and what do you do?" and the mouse says "I'm an input device, and I do mouse things." If you just try hook your OP-1 up directly to another USB MIDI device via some jankety and creative cabling, both devices will sit there waiting for someone to say "what are you."
The simplest (and cheapest, since you already own it) USB Host you can use is the laptop you already own. This will handle talking to the OP-1 and routing the signal to any other USB MIDI device you own. If you want to use the OP-1 with another USB MIDI or MIDI DIN device without a laptop, you will need to purchase something like the OPLAB, iConnectMIDI4+, Kenton USB Host, or CerebelUSB MIDI thingy. Each have their own feature sets that may or may not be useful to you, so research what is worth the money to you. Some also connect to iPads and iPhones for app connectivity. If you just want to connect an iPad/iPhone with the OP-1, several OP-1 users have purchased the Apple USB Camera Connector and have had success.
If you would like to be DIY about it, you can fool around with a Raspberry Pi or Arduinos and get the same functionality.
TL;DR - If you want to connect the OP-1 to another USB MIDI or MIDI device, you need a USB Host. There is no way around this.