The art of combining a small number of basic paper folds to make intricate designs is traditionally linked to Japanese culture. However, since almost any laminar material that will hold a crease can be folded, the term origami is often used nowadays as a generic term for all folding techniques regardless of their origin.
A number of technically advanced projects use such folding techniques. Examples include origami stents to enlarge clogged arteries and foldable antennas to make flexible electronic gadgets where the properties of the gadget may depend on how the antenna is folded. Researchers from the University of Texas at Austin have used origami-based folding methods to develop an origami Paper Analytical Device (oPAD) which could be used to detect diseases or analyse body fluids to give a quick diagnosis without technical skills or costly laboratories. Meanwhile, at Wyss Institute (Harvard) they used Origami DNA which is a process whereby the folding of a long single strand of viral DNA is supported by multiple smaller ‘staple’ strands to form various shapes including three-dimensional structures. The technique has been used to create lockable clam-like cages (nanorobots) which could carry drugs to specific targets and then be ‘unlocked’ to deliver the dose where it was required.
In contrast to these origami-inspired hi-tech applications a recent report in the journal Nano Energy describes how a Binghamton University engineer has developed a battery that is not only made by folding a sheet of paper but can be powered by a drop of dirty water. Before the paper is folded into a square the size of a matchbook, one side is coated with an inexpensive nickel-based solution to form an air-breathing cathode and the other side screen printed with a carbon-based paint to create an anode. The total cost including the paper was about five cents.
Power to the battery is generated from bacterial respiration, the bacteria being freely available in any type of organic matter including dirty water. The bacteria-containing solution is added into two common inlets of the folded battery, through which it is transported by capillary action. In use, the battery is unfolded to expose all the cathodes to the air, thereby maximising the reaction. The battery does not produce a lot of power but a couple of microwatts would be enough to power the sort of paper-based biosensor used for disease control and prevention in remote areas that have limited resources. The use of paper biosensors has been explored before but they had to be designed to work with some kind of handheld device providing the power. A self-powered system using a paper-based battery would not require any additional electronics to function.