Many future inventions will be designed to address problems, and to provide creative ways of dealing with them. Some of these problems relate to human beings, their health and lifestyle, and some bear on concerns about the planet, and will be designed to make it a better place. Here is my fourth list of inventions that might well feature in our near future:

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16.  Bugs to break down plastic. Current concerns about plastic in the oceans and perhaps in the food chain might well lead to less use of non-degradable plastics, but there remains the problem of dealing with the quantity already in the oceans. While remote minesweeping-like robots might be deployed to mop up some of it, a genetically engineered organism designed to digest and degrade plastic might afford a simpler and more viable solution.

17.  People-carrying drones. People have talked for at least seven decades about flying cars, and many prototypes have been built and flown. None succeeded because they had the drawback that people imagined a car sprouting wings and taking off down a runway like an aeroplane, with the driver needing a pilot's licence. We need people-carrying drones that can take off and land vertically, perhaps from the tops of buildings. Having the machines controlled by artificial intelligence could solve the old problem of the complexity of three-dimensional traffic control.

18.  Mechanical mental control. Primitive versions of this exist in which people have their brain waves amplified to turn a light switch on and off. They wear a skullcap with metal plates to monitor their brain activity, which is amplified to send a signal to the switch relay. We need a more sensitive version, perhaps an ear-stud, or even a chip inserted under the skin behind the ear, to allow the user's mental activity to turn switches on and off, to fly drones, and to control other machines by thought.

19.  Constant diagnostic health monitor. Many medical threats can be treated and alleviated if detected sufficiently early. A health monitor could be worn, or placed in the body cavity, to send constant feedback of heart rate, blood pressure, blood cell count, and other diagnostics. The information would be sent periodically to a central computer that could then alert the patient or their medical authorities if early warning signs indicated a problem.

20.  Bering Straits bridge. This is not, strictly speaking, an invention, but a work of engineering that will require much inventiveness and ingenuity. Russia is closest to Alaska in the United States across the Bering Straits. Such a bridge would be a huge challenge, but Russia in 2011 committed itself to $65bn for such a project. One proposal is for a bridge to span the 25 miles from Alaska to the Diomede Islands near the middle of the Straits, then a tunnel to connect it from there to Russia. The bridge might take the form of an enclosed elevated tube. The project would give land access between America and Russia, and later China, and the challenge would undoubtedly symbolize an interconnected world.