It's kind of ick, but science may have defeated the scourge of the skid mark.
Chinese researchers have developed a non-stick toilet bowl surface that could make the loo brush redundant.
A team from the Huazhong University of Science and Technology say they've created a new toilet bowl that will repel almost any substance.
Using 3D printing technology, the researchers fabricated what they call an abrasion-resistant super-slippery flush toilet (ARSFT).
Eye-catching demonstrations show "dyed synthetic faeces" sliding seamlessly down the bowl.
They report: "Flush toilets waste a significant amount of water every day due to the unavoidable adhesions between human waste and the toilet surfaces.
"Super-slippery surfaces can repel complex fluids and various viscoelastic solids, however, are easily broken by mechanical abrasions."
A paper published in Advanced Engineering Materials this month describes: "Unlike traditional super-slippery surfaces with limited thicknesses which can be easily worn away, the powder-sintered strategy endows the ARSFT not only with a self-supporting 3D complex shape but also with a porous structure that can accommodate considerable lubricants for an abrasion-resistant super-slippery property.
"As a result, the as-prepared ARSFT remains clean after contacting with various liquids such as milk, yogurt, highly sticky honey, and starch gel mixed congee, demonstrating excellent repellence to complex fluids."
Besides liquids, the team claim ARSFT exhibits a high resistance to sticky synthetic faeces.
They write: "Notably, even after being abraded to 1,000 cycles of abrasion using sandpaper, the ARSFT maintains its record-breaking super-slippery capability.
"The concept of the 3D-printed object with a superior abrasion-resistant slippery ability will improve the development of super-slippery materials and further save water consumption in the human society."