Bio-ink printing

A multi-fluid live cell printing system comprising:

• a first bio-ink reservoir containing a first bio-ink, wherein the first bio-ink comprises:
• a first type of live cells,
• a buffer solution that is suitable for live cells, and
• a polymer comprising polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl sulfate, polyethylene glycol, polyester, poly(dimethylsiloxane), cellulose, polysaccharide, or a combination thereof;
• a second bio-ink reservoir containing a second bio-ink, wherein the second bio-ink comprises a buffer solution that is also suitable for live cells;
• a first bio-ink ejector to eject the first bio-ink from the first bio-ink reservoir, wherein the first bio-ink ejector comprises a first ejection nozzle and a first thermal resistor positioned to heat the first bio-ink to form a vapor bubble to eject a droplet of the first bio-ink from the first ejection nozzle;
• and
• a second bio-ink ejector to eject the second bio-ink from the second bio-ink reservoir.