Scientists Use Microspheres to Fabricate Artificial Molecules

A new method to develop complexly arranged tiny objects combined with microspheres has been discovered by a group of scientists at IBM Research Zurich and ETH Zurich. These tiny objects are only a few micrometres in size and are formed in a modular manner, allowing their design to be programmed so that every single component displays a wide variety of physical properties. This is followed by introducing the micro-objects into a solution through a very simple step after the fabrication process.

Currently available micro 3D printing technologies enable the objects to be created only if they have a single material and a uniform structure, and they also need to be fixed to a surface during the production stage.

The scientists developed the micro-objects using very small silica or polymer spheres as their building blocks. Each sphere had varied physical properties and a diameter measuring about 1 µm. The scientists were able to monitor the particles and organize them in the specific geometry and sequence.

The resulting structures occupy a unique slot in the size scale: the structures appear to be a lot bigger than the conventional biochemical or chemical molecules, but are even smaller in size compared to the conventional objects that exist in the macroscopic world.

Depending on the perspective, it's possible to speak of giant molecules or micro-objects. So far, no scientist has succeeded in fully controlling the sequence of individual components when producing artificial molecules on the micro scale.

Lucio Isa, Professor for Interfaces, Soft Matter and Assembly, ETH Zurich

Diverse Range of Applications

The new method is suitable to develop micro-objects with defined non-magnetic, magnetic and differently charged areas. At present, it is possible for the scientists to develop rods that are small in size with varied composition and lengths; standard 3D objects; and extremely small triangles. The scientists are planning to study self-propelled micro-carriers that are capable of moving in an external electric field due to their material composition and advanced geometry.

A few other possibilities include the use of micro-mixers suitable for lab-on-a-chip, or micro-robots for biomedical applications, which allows grabbing, transporting and releasing a number of specific micro-objects. In addition to this, it is also possible to design artificial molecules that interact with one another and then independently arrange themselves into bigger superstructures. This is more relevant for photonics involving light-based signal processing.

Customized micro-structures are required in photonics. These could one day be manufactured with our components.

Lucio Isa, Professor for Interfaces, Soft Matter and Assembly, ETH Zurich

Production with Micro-Templates

To simultaneously manufacture an increasing number of similar micro-objects, the scientists used polymer templates containing engraved indentations taking the form of the object to be produced. The scientists developed a new technique that permitted them to deposit a small sphere at a time during every single step of the entire procedure. By selecting the specific type of sphere for based on each step, the scientists can construct bigger objects in a sequence. All the small spheres were then heated to link them together.

In the development phase, these small spheres are strongly linked to each other, but in the future, the scientists are planning to use soft bonds to connect these small spheres. This leads to the possibility of using the objects as large-scale models for biochemical and chemical compounds, and hence enabling the study of protein folding on an innovative level.

In the future, the scientists also plan to arrange the objects containing small spheres developed from materials other than silica or plastic.

In principle, our method can be adapted to any material, even metals.

Lucio Isa, Professor for Interfaces, Soft Matter and Assembly, ETH Zurich