I can understand them being able to actually arrange the pre-grown cells onto a scaffold for growing organ, but will the printers ever actually be able to print the cells themselves? What would be the difficulties trying to do this, seems like it would be like trying to print a water balloon for the most part, hard to do, hard to keep it together as you are doing it.

I wasn't sure whether I should have posted this here, or one of the biology forums.

One could in prospect print the cell frozen, and thaw it.

 

But there is a more serious problem: cells are structured in details too fine to resolve by light or similar low energy radiation. There is a reason for the electron microscope.

I can understand them being able to actually arrange the pre-grown cells onto a scaffold for growing organ, but will the printers ever actually be able to print the cells themselves? What would be the difficulties trying to do this, seems like it would be like trying to print a water balloon for the most part, hard to do, hard to keep it together as you are doing it.

What holds human cells together?

 

http://answers.yahoo.com/question/index?qid=20080109122114AAHUJzT

Printing of 3-5nm gold structures onto silicon has been done using electron beam lithography. Cells are larger. However, we have no idea how to make a cell, much less make one that is alive. Thus, the OP question cannot be answered at this time.

What EdEarl said. In addition, 3D printing usually involves the deposition of only one substrate and electron beam lithography is more like etching something out of a substrate. However, a cell has thousands and thousands of different components that cannot be broken down to a common monomer. Thus even if we knew precisely what we need to create a viable cell (which we don't) we would also have an idea how to deposit thousands of different proteins, sugars, lipids etc. at a given position in space.

Perhaps theoretically a sufieciently advanced electron tunneling microscope could deconstruct a cell atom by atom recording all there locations to make replicas. But it took 4 researchers 2 weeks of 18 hour days to create the "boy and his atom" video.

http://www.youtube.com/watch?v=oSCX78-8-q0

 

So it it would take much longer to assemble the Trillions of atoms in a cell. An automated 3d atomic printer that could precisely place atoms of various kinds in paralel and rapidly enough to produce a single cell in a human lifetime would be a amazing and revolutionary technology.