Continuing in the vein of analyzing the potential applications of non-polymeric and non-organic materials in the field of nanorobotics, it is time for us to investigate a relatively new class of material, bulk metallic glass, which shows extraordinary promise in an array of biomedical applications.
Bulk metallic glasses (BMGs) are amorphous metallic alloys that combine the high strength of metallic materials with the flexibility and processability of polymeric materials. Due to their unique, glassy properties, they can be pressure molded or blow molded into various shapes. This allows engineers to create structures considered impossible to form with conventional metallic materials. They can be patterned on multiple length scales to carry out various functions. Such nanopatterning allows the material to better resist the classical foreign body response and fibrous encapsulation. BMGs, specifically Pt-based BMGs, are notable for their high strength, elasticity, corrosion resistance, and unique processability, all of which indicate they are a promising alternative to conventional metallic implants.
Thermoplastic forming of micropatterned BMGs
The ease of manufacturing nanoarchitectures with BMGs makes them an area of increasing interest for biomedical and structural engineering researchers. Aside from established methods of pressure (thermoplastic) and blow molding, BMGs could be fabricated via other methods to create unique 3D nanostructures. These structures could have potentially limitless uses in medicine and structural engineering. One such method of creating novel 3D nanostructures is known as two-photon lithography: A laser is used to “write” a three-dimensional pattern in a polymer by crosslinking and hardening the polymer wherever the two meet. Once patterned, the non-crosslinked portions of the polymer are dissolved away, revealing a three-dimensional scaffold. Next, the polymer is coated with a continuous layer of a material (in this case, bulk metallic glass). Finally, the polymer is etched from within the structure, leaving a hollow architecture behind. There is a great degree of freedom in designing the polymer structure onto which the BMGs are coated. These nanoarchitectures even have the potential to form scaffolds or bodies for the “real-deal” Nanorobots I mentioned in my first post.
The metallic nature of BMGs means that these nanoarchitectures could be outfitted with simple circuits. Like metals, BMGs have high conductivity and magnetic properties. Taking advantage of these properties, one could fabricate a BMG nanostructure with built-in logic circuits relying on magnetic and electrical interactions that would enable it to carry out basic commands given certain environmental stimuli.
In a recent review of BMGs, researchers from Cambridge looked at the potential uses of BMGs in biological applications. They theorized that the development of nanometeraccurate linear actuators using BMGs is highly possible and quite desirable. Such devices could be used for accurate positioning of cell-operation manipulators in the biomedical industry. They assert that soft-magnetic BMGs are appropriate materials for the magnetic yokes of such linear actuators. (1)
BMGs can also be used in more convention nanotechnologies. The easy manipulation of their structure allows them to be engineered as porous drug-eluting stents or nanoparticles. However, unlike polymeric nanoparticles, they would have unique electrical and magnetic features, be relatively bioinert, very strong, and would not break down.
As you can see BMGs are a very interesting material with unique properties that can be leveraged to do things at the nano-level that no other current materials are capable of.
