Inorganics

||Acoustics

Standing waves have node locations that do not move. This principle was used in a demonstrative example to align nanowires into a square array. Alternating current was delivered to four piezoelectric transducers oriented in a square.

||Oragami

Typically becoming popular for micro-structures, oragami type assembly of connected template-like objects could be carried out in several ways. One instance is where silicon could be folded and unfolded with the introduction of water droplets to the wafer.

||Self Assembly

At the nanoscale, it is difficult to manually manipulate and arrange certain entities of interest. Therefore, in most cases, we rely on physics and chemistry to do the work for us. In the more simple case of nanoparticles, we can functionalize their surface and in essence create tethers or molecular links. These links can interact to bring the nanoparticles closer together in a determined manner.

||Self Assembly – Light Induced

Some molecules may greatly absorb incident electromagnetic energy. Upon doing so, the energy level of the molecule may change and cause a subsequent isomer transformation. In the case of a gold single-nanoparticle chain, the dicyanide trimer was directly observed to be responsible for the bent-to-linear transformation as well as linking into longer oligomers.

A tweezer effect may also be used to position nanostructures and quantum dots. The action is related to the accumulated recoil of incident photon momentum. Biologists, for example, use this effect in optical tweezers to fix cells and rotate them at the focus of a microscope. Physicists can also use the tweezer effect to isolate and collide Rb atoms at a velocity of about 1m/s and temperatures of one millionth of a degree above absolute zero.

Furthermore, gold nanorods may be positioned more regularly outside of their normal bonding symmetry by light induced plasmonic vibration. This process was found to occur in aqueous solutions although could readily explain ablation-generated plasmonic nanostructure.

||Self Assembly – DNA Mediated

DNA is composed of two complementary strands which are attracted to each other through matching base pairs. This attraction between the two strands can be used for the DNA-mediated self-assembly of two different nanoparticles into large-scale nanocomposite arrays. Synthetic DNA strands are attached to the nanoparticles of interest and the strands are allowed to naturally pair up, causing the nanoparticles to self-assemble into 3-D superlattices. This technique makes it possible to mix nanoparticles with different magnetic, optical or chemical properties and their self-assembly can be controlled to produce new enhanced or multifunctional materials.

Organics

||Nanofibers

A mixture of duplex and quadruplex DNA subunits resulted in fibers from 250 – 2000 nm in length. These strands appeared to be stiffer than those made solely from duplex subunits, which should lead to improved DNA patterning for the creation of new multi-functional nanomaterials.

||Self Assembly – Light Induced

As with inorganics, it is found that two peptides (small proteins) may change shape upon irradiation with light, thereby allowing or preventing a specific protein-protein interaction. This light activation concept was also developed with micro-scale stimuli-responsive hydrogels to release therapeutic agents in a patient’s body. Magnetic navigation of such micro assemblies with MRI equipment is also deemed possible.

||Tweezers

Strands of DNA can pivot at a certain point with a specific DNA sequence acting as an actuator to close and open the 16 nm gap. This tweezer effect can bring, for example, an enzyme on one end and a cofactor on the other end together and in essence catalyze their reaction.

||Vault particles

Vaults are barrel-shaped nanoparticles found in the cytoplasm of mammalian cells. It may be assembled by revolving about 78 major vault proteins. The 100nm particle has a large interior space and is appeared to be biodegradable.

Systems

||Integrated circuits

Copper was introduced in chip production in the early 2000’s to replace aluminum. Now copper is facing replacement as making wires or pillars on the nm scale as reaching its limit in electrical conduction and heat dissipation. For carbon nanotubes, remote plasma chemical vapor deposition is used with the CMOS chip manufacturing technique to grow CNT bundles in vertical contact holes of 150 nm diameter on 200 mm silicon wafers that connect to copper contacts. An insulator is used to fill the gaps between the CNT bundles as well as to fix the CNTs so that their ends are trimmed to be level with the surface.

||Welding

At room temperature, graphene transistors may be used, but require a working size of a few tens of atoms in width. These transistors will need atomically precise electrical contacts. To do so, voltage pulses from the tip of the STM can remove a single hydrogen atom that initiates single bond formation.

Links

• Au nanoparticles // self assembly – light induced
• Enzymes // tweezer – DNA
• Graphene electrodes // welding

At Open ND (TM)

As people in a busy society, sometimes we wish certain things could be done on our behalf and to simply our lives. In one such instance, laser plume dynamics influence the way ions and quantum materials interact with each other to rapidly produce stunning nano-architecture. This means that we can create nanoparticles in one experiment and nanorods in another simply by modifying the physics of the plasma. Since rules of nature are observed, minimum intervention is necessary and the reproducibility and quality of the results are improved. Our assembly methods and many other interesting ones can be viewed in this section.