Asier Marzo, a researcher at Bristol University, made this amazing project where you can make your own DIY handheld tractor beam. Currently it holds only small objects like liquid droplets or small insects.
It is Arduino controlled, cheap to make and uses ultrasonic sound emitters to produce the tractor field. You can make it for some 70 USD and with basic electronics skills. Ideal educational or school science project.
Here is a video of the device in action with some construction instructions:
It is like simplified home made sonic screwdriver from Doctor Who :-) Here you can see a small red liquid droplet floating in 3d printed sphere that holds ultrasonic transducers.
Step-by-step build guide with all the files and the code:
Detailed research paper with the science behind it and device design:
You can also find different type of the same device developed by the same author. It is a horizontal 3d printedplate array of ultrasonic emitters that make small objects levitate.