The Flash has introduced a new development regarding the Artificial Speed Force in order for Barry Allen to continue having his speed. Ever since Crisis on Infinite Earths, Barry has had to figure out how to still be a speedster after the Speed Force died because of the events of the Arrowverse crossover. Without the powerful energy source, Barry and the team decided to pursue creating their own artificial version of the Speed Force. But creating something that massive is easier said than done as it comes with its own set of challenges.
The only way they were able to power it up was through Nash Wells' sacrifice as his body is the host for all the surviving versions of Harrison Wells in the Multiverse. Together with all of their Multiverse particles inside of Nash, they made it possible to get the Artificial Speed Force working. While it was a tragic sacrifice, it didn't go as well as Team Flash had hoped. Despite getting the ability to speed-think, it cut The Flash off from his emotions, making him less human the more he used that power.
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Because of it, Barry destroyed the Artificial Speed Force so that he could become himself again, even though it cost him his speed. However, The Flash presented a new solution that took a season 4 episode and brought it full circle. In the episode "Run, Iris, Run," Iris West temporarily became a speedster, which became crucial 3 seasons later. Because she had the original Speed Force in her once, there was still a part of it inside her that they could use. This made Iris the key to powering up the Artificial Speed Force without Barry getting disconnected from his emotions again, but the new Artificial Speed Force also had other differences from the other Speed Forces featured throughout the series.
What sets the Artificial Speed Force 2.0. apart from the original Speed Force, the Negative Speed Force, and even the ASF 1.0.? The Arrowverse take on the Speed Force is that it was created through tachyon particles that have been infused with dark matter. Its actual origin and construction is to this day still a big mystery. The Negative Speed Force, which was created by Reverse-Flash, runs on every non-positive emotion. Hate, fear, and sadness are how it feeds and allows a speedster to get access to it, but only if they give in to those emotions. The initial Artificial Speed Force, while functional, was constructed in a way where it couldn't lead to emotional fallout, leading to its own problems in removing Barry's emotions.
That's why The Flash began to lose himself the more he used his speed-thinking power. The latest ASF model, however, feeds off the original Speed Force and thus doesn't compromise Barry's or other speedsters' behavior. It's a neat way to tie it back to The Flash season 4 episode where Iris got to have speed, making it an even more important plot development years later. Originally, its only lasting impact was that Iris's purple lightning is why she and Barry's daughter, Nora West-Allen, has both of their lightning colors. Now, it's also become the solution to getting the new Speed Force to work the way it should. It also lets The Flash highlight once again Iris West being Barry Allen's lightning rod in a way that is now instrumental to the Artificial Speed Force and Barry's future.