the voltage rating of capacitor is given by manufacturer to safeguard puncturing of dielectric by peak to peak voltage and damage the capacitor, when it said 50v it means 50v peak to peak. the higher the voltage rating the better it is but more expensive you have a 9v dc circuit (as measured by dc voltmeter) this means you applied 9v average to the capacitor AVG volt = 9 PEAK volt = (AVG)(pi) / 2 = 14.12 v PEAK to PEAK volt = (2)(PEAK volt) = 28.24 v your minimum capacitor rating is 28.24 v suggest use 50v capacitor the capacitor voltage will not affect the circuit operation, it is still 22uf except thicker dielectric material, physically bigger size.
microelectronics is when you are making extremely small devices to accomplish tasks, like making a robot the size of a mosquito or something. Nanoelectronics is making devices at cellular sizes. Nanoelectronics may be the future of medicine. They have the ability to replicate themselves, so you send a few into a person with a needle injection, to attack and destroy a tumor, or repair a ruptured spleen or something. Nanoelectronics is both amazing and a little scary. But very cool.