What is the following researches about zapping brain to help people enter mental flow?

I am reading Homo Deus:A Brief History of Tomorrow by Yuval Noah Harari and he mentioned a research about zapping brain to enter mental flow in his book, and I find the original news here , The study focused on a technique called transcranial direct current stimulation (tDCS), which involves applying a weak electrical current to specific areas of the brain.I think such technology is insane and can greatly help to enhance study, I think if such technology can be combined with enough fish oil to enchance brain energy and Transcranial magnetic stimulation to enhance memory ability, a new era of human learning will come,but I can't find any following study of this, it is disappointing