With an initial six custom particles that predictably interact with one another in the presence of AC electric fields of varying frequencies. The study could form the first steps towards designing advanced applications such as artificial muscles and reconfigurable computer systems.
"We've engineered and encoded multiple dynamic responses in different microparticles to create a reconfigurable silicon toolbox," said first author, Ugonna Ohiri. "By providing a means of controllably assembling and disassembling these particles, we're bringing a new tool to the field of active matter."
Engineering particles from silicon presents the opportunity to physically realise electronic devices that can self-assemble and disassemble on demand.
"Most previous work performed using self-assembling particles has been done with shapes such as spheres and other off-the-shelf materials," said Professor Nan Jokerst of Duke. "Now that we can customise whatever arbitrary shapes, electrical characteristics and patterned coatings we want with silicon, a whole new world is opening up."
The researchers explained that they were able to fabricate silicon particles of various shapes, sizes and electrical properties and characterised how these particles responded to different magnitudes and frequencies of electric fields while submerged in water.
Based on these observations, they fabricated new batches of customised particles that were likely to exhibit the behaviours they were looking for, resulting in six different engineered silicon microparticle compositions that could move through water, synchronise their motions, and reversibly assemble and disassemble on demand.
The thin film particles are 10-micron by 20-micron rectangles that are 3.5 microns thick. They're fabricated using Silicon-on-Insulator technology. Since they can be made using the same fabrication technology that produces integrated circuits, millions of identical particles could be produced at a time.
"The idea is that eventually we're going to be able to make silicon computational systems that assemble, disassemble and then reassemble in a different format," said Prof. Jokerst.
Some of the particles were fabricated with both p-type and n-type regions to create p-n junctions – common electrical components that allow electricity to pass in only one direction. Tiny metal patterns were also placed on the particles' surfaces to create p-n junction diodes with contacts. The researchers believe this could lead to engineering particles with patterns using other electrically conductive or insulating materials, complex integrated circuits, or microprocessors on or within the silicon.
