Invert Robotics has just closed another big fundraising round, this time bringing in $US8.8 million ($13m) at a post-money valuation of around $35m.

The Christchurch-based startup has made a splash over the past couple of years with its robots that can climb - and clean - non-magnetic services such as stainless steel vats, or glass or aluminum surfaces.

The competition has traditionally used magnets for climbing. Invert Robotics uses suction to create a vacuum to "climb like a snail, not a monkey."

Its robots are now being used clean equipment by seven of the 10 largest dairy companies in the