As a student at the University of Bristol, Tom Carter became obsessed with a seemingly impossible notion: letting people feel and manipulate virtual objects. A professor turned him on to an esoteric concept — using ultrasound to simulate tactile sensations — that was floated and abandoned back in the 1970s.

Today, Carter, 29, is co-founder and chief technology officer of Ultrahaptics, which uses clever algorithms and an array of ultrasound emitters to simulate a range of feelings: tiny bubbles bursting on your fingertips, a stream of liquid passing over your hand, the outlines of three-dimensional shapes. Carter says dozens of companies making everything from computer games to cars and appliances are testing the technology, an example of what computer scientists call haptic feedback (haptic in Ancient Greek basically meant "coming into contact with something").

While other tech companies are working on their own versions of haptic feedback, Ultrahaptics says it is the only one that lets people feel and manipulate virtual objects in the air. There are many potential applications — using an invisible slider to pump up the bass on a home stereo, adjusting the car air conditioning with the twist of a virtual dial — but Carter said the technology's greatest promise may lie in making virtual reality "feel" more real.