Making small moving parts is usually more challenging than making larger ones. In robotics this is a challenge when there is the need for a robot to manipulate small objects.
And this is what researchers at the Iowa State University have set up doing.
Rather than developing very small "fingers" they turned to Nature and developed micro tentacles.
Using "fingers" you need to be aware of the amount of pressure to exercise on the object you want to pick up and depending on its surface you need to change the pressure (a hard surface with no elasticity requires quite a different handling than a soft surface...). On the contrary, using a tentacle you can gently wrap it around and use basically no pressure whatsoever (the pressure will be the result of the weight of the object once you hold it.
The tentacles are fabricated from tiny tubes just 8mm in length and less than 0.2mm in diameter. They are made of a transparent elastomer that is sealed on one end. Air can be pumped inside and given the asymmetrical structure of the tubes it cause them to bend in a spiral.
Nature provides plenty of examples of using tentacles, and don't think just of octopus: many plants use tentacles that spontaneously bend once they hit a hard surface.
Most of the efforts was focused on finding a way to produce these microtubes in volume and at affordable price, and this is what they achieved to do. According to the researchers these tentacles are very good in the emerging area of soft-robotics.