I was working on a microfluidic device so I was wondering if an array of very little solenoids (at least in the sub millimeter range) is already available for sale to create a little field when you fire it. I've googled everything came up in my mind yet and found nothing, maybe someone with wider experience can help me. I'm not english so I could have missed some key search words while googling around.
"Solenoid" in English can have a couple of meanings:
The most common meaning is an electro-mechanical device which has a wire-wound coil and a central pin or rod which is moved by the magnetic effect of the current in the wire. This is used to strike a bell like a doorbell or maybe actuate a larger device such as a hydraulic or pneumatic valve.
The less-common meaning is just the wire-wound coil. That can often be called a solenoid. If you have an electrically-controlled industrial valve, then you might be looking to replace a burned-out coil, in which case you should search for a replacement solenoid.
It sounds like maybe you have the valves already but you need to add the electronic control to the valves? Or maybe you should be looking for "solenoid valve" and variations like "electrical control valve"?
Some more details on your project like a picture or diagram would help us to help you search.
Wait a minute, I'm not english but by this I mean that I could have not used the search terms that fit perfectly what I need.
Anyway, what I need is a solenoid wrapped around a piece of ferromagnetic material so that when electric current cross the solenoid it creates a magnetic field. I need its dimensions to be at least on the submillimeter scale so I can create a pretty dense array. I hope I've been clearer. Thank you so much for your reply.
I would imagine this is a very specialist area and such devices are always custom designed
and custom manufactured.
I found this research paper from a few years back: http://iopscience.iop.org/article/10.1088/0960-1317/23/11/114009
Can you say what you wish to do with this device ?
A micro solenoid as you describe will have little force.
Perhaps another technology would be more appropriate.
Perhaps Piezo or Bubble Jet technology.
Hi,
Anyway, what I need is a solenoid wrapped around a piece of ferromagnetic material so that when electric current cross the solenoid it creates a magnetic field.
"Anyway, what I need is a coil wrapped around a ferromagnetic core so that an electric current induces a magnetic field in the core."
I hope that clears the description up.
I would say you are going to have problems with a "submillimeter" size.
How small, and what magnitude of magnetic flux do you require?
Tom.. 
http://www.computerhistory.org/storageengine/thin-film-heads-introduced-for-large-disks/
You can make electromagnetic coils really small if you have the technology.