These can be combined with 3D displays to create a 'haptic hologram' 

It could have practical applications, such as allowing surgeons to explore a CT scan by enabling them to feel a disease

A Star Trek-style holodeck could be closer to reality following the creation of a system that lets people feel holograms with their bare hands.

Using ultrasound to precisely project sensations through the air, users can 'feel' and interact with virtual objects.

The firm behind the system says it could even allow surgeons to reach 'inside' a hologram of a scan and feel tumours.