Liquid printing is virtually ubiquitous thanks to inkjets, but the materials can only be so sluggish before it stops working. What if you wanted to print a biological material, or even liquid metal? That might happen soon. Harvard researchers have developed a technique that uses acoustic levitation to print droplets of materials that wouldn't normally be so accommodating, including metal and honey. The approach uses a subwavelength acoustic resonator to create a sound field that pulls substances from the printer nozzle at over 100G -- even some of the most viscous materials can't resist that tug. You can control the size of the droplets using the amplitude of the soundwaves, and place them anywhere you like.
Despite the seeming violence, the system (known as "acoustophoretic" printing) is safe to use with living biological material as the soundwaves don't propagate through the droplet. You could print living cells if you wanted.
It's still early days for the project, but there's a lot of potential. Harvard sees this as most useful for the pharmaceutical world, where it could lead to drugs (including biopharmaceuticals) that weren't possible before. However, it could also have uses in shaping new conductive and optical materials, or even everyday purposes like new cosmetics and food. Substances that were once difficult to include in tiny quantities could eventually make frequent appearances in everything from medicine to hot sauce.