maybe something related to healthcare... that's growing and will continue to grow as people get old.
Maybe electro-bio-mechanics to help people with physical disabilities, arthiritis and the like (old-age diseases), mobility problems,
or for soldiers going to war (force multiplication, so called "iron man" suits)
maybe embedded electronics, hearing aid, eyesight, pacemakers, automatic insulin management/injection for diabetics, heart problems
Internet of Things (IOT), everything connected, mesh networks
miniaturization (everything getting smaller)
ultra low power (everything getting powered by even smaller batteries, and users want 1001 features and more than 24 hr battery life for their small devices)
maybe auto-regenerative power, no more need for re-charging (kinda like those automatic wrist watches that don't need rewinding)
security, encryption
autonomous systems, and human assisted machine learning, AI
renewable energy, solar efficiency is still very poor, battery efficiencies are still poor