The usual short legal answer is no.
You do not need working examples to patent an invention in the USA. However, that is a dangerous and often impractical answer.
In my opinion, the answer to this question varies by country.
In the USA, you are not legally required to provide working examples in your specification if you can tell a person skilled in the art how to make and use your invention. However, if you have a chemical or biotech invention, then the Examiner may reject your application, alleging that it is not enabled. That is, they do not believe that you can do what you say you can. And without working examples, you can find yourself in a very costly argument. One that you probably will not win.
However, if you have working examples, you can usually win this argument every time or even avoid it altogether. That’s because it’s hard to argue with success. It’s easy to argue with a lack of it.
Similarly, you would be wise to have working examples for Europe because it can be difficult to narrow your claims from broad embodiments of your invention to narrow ones. This means, you cannot easily disclose every possible variation of your invention that might work, and then try to narrow your protection to those versions actually work later. Again, this a huge problem for getting chemical and life sciences patents in Europe. If you want to protect your invention in Europe, it is best to know exactly what works and what doesn’t before you file your first patent application anywhere.
Getting a chemical, pharmaceutical, or life sciences patent in Japan, China, and South Korea can require even more working examples. In Europe, they might not let you narrow your claims to the best embodiments. In Japan, they tend to push back on any patent protection for groups of products that you do not have a working example for. Want to patent 10 groups of molecules? Then you might want to provide 10 working examples to support your claims.
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