Energy

||Batteries

The basic components of a battery include:

  1. an electrolyte to provide electrons,
  2. an anode to discharge those electrons, and
  3. a cathode to receive them.

A pure lithium anode would significantly improve efficiency over currently available lithium electrolyte products with graphite of Si as the anode. One barrier to a lithium anode has been the swelling of lithium and the creation of dendrites that short the circuit and reduce battery life. A protective layer for a lithium metal anode is under development that needs to be chemically stable to protect against the chemical reactions with the electrolyte and mechanically strong to withstand the swelling.

Sodium is more environmentally benign than lithium as used in rechargeable batteries. Diffusing sodium ions through tin anodes often weaken the tin’s connection to its base material. However, the wood fibers are soft enough to serve as a mechanical buffer, and thus can accommodate the swelling and shrinking of the tin nanocoating up to 400 cycles. Additionally, wood fibers that make up a tree once held mineral-rich water, and so are ideal for storing liquid electrolytes.

||Flexible electronics

In an effort to replace silicon wafers, flexible polymers (i.e. organic field-effect transistors) need to pack into crystalline structures containing regular pathways for charge carriers. It is found that fluorenone carbonyl units have the following advantages:

  • makes electrons in the co-polymer’s highest energy states less accessible and therefore less susceptible to air-based impurities;
  • helps to stick to aromatic hydrogen atoms; and
  • improves solid state packing.

Flexible and wearable electronics may allow for a wide variety of human-machine interfacing applications. To overcome the difficulty of using brittle Si, the textile may the dipped into an aluminum solution that will form metal fibrous networks with the help of a Ti catalyst. Polymers may also have embedded NPs of gold that align as they the material is stretched. This provides the material a conductivity of 35 S/cm even when stretched at 5.8 times its original length (enough for small devices).

Graphene inks are also an alternative and can be printed on paper. Carbon in general is an attractive material because wires made from carbon are 10 times lighter and up to 30 times stronger than copper. Carbon wires also have the added benefits of corrosion resistance, a higher current capacity and lower losses in transmission efficiency with increasing temperature. Their conductivity is yet to match copper, however, due to the discontinuity of the individual CNTs.

||Friction

Super-lubricity is a theoretical concept  in overcoming friction on the microscopic scale. It is found that along a twist boundary (shear interface) of carbon, the atoms are misaligned which avoids crystal locking. The result is being able to translate at 25m/s (90km/h) on a micrometre squared area.

Friction is also found to be tunable at the nanoscale. By varying the thickness of the SiO2 layer, the forces experienced by AFM scanning could vary up to 30%.

||Hydrogen

Unlike hydrocarbon fuels, such as oil, coal and natural gas, where carbon dioxide and other contaminants are released into the atmosphere when used, hydrogen fuel usage produces pure water as the only byproduct. Nanoscale water electrosis may be facilitated by nanoparticles that mimic photosynthesis. In essence, an efficient separation of hydrogen from water occurs.

||Light

Biological systems on Earth demand light for energy, including the critical photosynthesis process. Solar energy harvesting is a ready application of nanomaterials. This is because it has most to do with surface science. The bandgap of a material is found to be affected by nanostructuring. For example, arsenic NP absorption from deep infrared to green is controllable by varying degrees of dimensional structuring. Core-shell gold NPs have also been found to convert a broad visible-invisible spectrum of light into heat that can be used for steam generation.

Synthesize the DNA of an Arabidopsis plant with genes from a firefly, and the result is natural luminosity. May or may not replace street lamps, let alone a table lamp, but applications are still vast for low cost or free electricity.


||Computers

Skyrmions are new magnetic structures which were discovered as a grid of magnetic eddies in a silicon manganese crystal. Individual eddies can also be generated on surfaces and moved electronically. Researchers are interested in using skyrmions to transfer magnetic information directly to materials through electric current alone, since they require 100 000 times less current and significantly less atoms per bit of information. Such an advancement would result in more compact and energy-efficient computers, but the method is still limited to very low temperatures.

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Communications

||Conduction

A quantum wire is about 100 atoms across. However, the conduction of electrons varies in a step-wise manner as the width or length increases. This is an effect of quantum mechanics, where the electrons follow standing wave patterns and are affected by each other’s presence.

||Quantum teleportation

Researchers have been able to teleport information from light to light at a quantum level since 2006. For example, there are two glass containers, each containing a cloud of caesium gas atoms. The two glass containers are enclosed in a magnetic field chamber and are not connected to each other. When the wavelength-specific laser light hits the atoms, the outermost electrons react by pointing up or down. The emitted photons carry this quantum information to the second container. In essence, this behavior mimics computer information delivered with the numbers 0 and 1.

||Image projection

Image and video projection from portable devices, such as cell phones, has been in the works for a while (in particular amongst the MEMS sector). The capability of such designs is limited to lenses and bulky (although micro-scale) mirrors.

By bending light, the use of lenses would not be necessary. This is the main motivation for integrated optical phased arrays (OPAs). It is so far possible to bend infrared light by manipulating its coherence from a single laser diode. Electrical currents would phase shift the light travelling through a silicon chip by influencing the number of electrons joining each light path. The light wave would then recombine coherently after being projected from a chip’s grid arrays.

||Transistors

Ultrafast processes are common at the nanoscale. To combine such processes with a high quantum efficiency–as well as manufacturing simplicity–is a major milestone in energy engineering. From an electronics point of view, transistors have revolutionized global markets for their brilliant electronic switching/amplification capabilities as well as their ever reducing size (up to millions on a single silicon chip). The new transistors will likely need atomically precise electrical contacts.

SiO2 is the most typical transistor material. A higher material dielectric constant is favourable to reduce electron leaking at nm thickness (quantum mechanical tunneling). Silicene transistors of one atom thin silicon are also being developed. Ge, HfO2, and TiO2 are promising materials but require intermediate layers to increase the band offset. Graphene transistors with double-layered striped channels show an improvement over Si in terms of electron mobility and operating temperature.

A new type of transistor uses a nanoscale insulator (boron nitride nanotube, also a popular piezoelectric) with Au QDs. Quantum tunneling, or electron hopping, occurs stably between the Au QDs at a sufficiently high voltage and under liquid helium cooling. It can also occur under plasmonic conditions where light excites surface plasmons, which are then tunneled between molecularly separated plasmonic resonators. The resulting operating frequency is in the scale of 100 THz, about 10,000 times faster than traditional computer processors.

CNTs can also take part in finding an alternative for Si. Usually grown in batches for these applications, some CNTs can be more conductive than semi-conductive with on/off properties. A way around this issue is to switch off the good CNTs first, then burn the conductive CNTs with a surcharge of electricity.

Using light, on the other hand, would address scalability and generated heat issues. One possibility is to use a set of mirrors separated by a wavelength of light. Doing so builds up strong EM fields makes and makes the mirrors essentially transparent. A “gate photon” can be used to excite a single electron of one cesium atom in a super-cooled gas. The higher energy state now would reduce transmitted light to as low as 20%. Alternatively, the Faraday effect exhibited by some materials (e.g. mercury telluride platelets) may be used to rotate the polarization of light at terahertz frequency (induced by a permanent magnet and applied voltage). Magnetite is an alternative material that shows conductive to non-conductive transitions with visible laser light excitation on the ps time scale.

With DRAM memory, each cell consists of a capacitor and a transistor linked to one another (as opposed to only a transistor for NAND Flash memory). Samsung developed a modified double patterning and atomic layer deposition method to scale this DRAM at 20nm, providing a 4Gb DDR3.

Our Nature

||Microbes

Nano-Ag has been used for different reasons in consumer and commercial products over the past century. Nanosilver has appeared in an increasingly wide range of U.S. products, including athletic clothing, bed and bath linens, cosmetics, baby bottles, stuffed animals etc. It’s also used in hospital equipment. In Southeast Asia, nanosilver is used even more commonly and often openly. It has been sprayed in Hong Kong subways promoted with Korean toothpaste.

Cu is a known antibiotic material and is recently found effective in treating drinking water, industrial effluent, sewage, and to reduce disease transmission in public places such as washrooms. The Cu NPs are attached to a vermiculite material which is a mineral that is stable and used under extensively as filler in fireproof materials, plastics, paints and lightweight concrete.

||Molecular Sensors

New age sensors promise to be simple, portable, disposable, low power-consuming and inexpensive devices. Nanotech-paper based sensors are particularly promising for their affordability. SWCNTs trapped in paper with Au electrodes shows a detection limit of 20ppm of ammonia gas with a quick response.

||Nature’s Own

Sapwood is comprised of xylem, a porous tissue that conducts sap from a tree’s roots to its crown through a system of vessels and pores. Such a pit-membrane is effective filters of contaminants. For example, a direct observation of 99% NP filtration down to 70nm is possible. This includes bacteria down to 200nm such as E. coli. This method could be used to treat up to 4L of water per day.

||Water

With over 50% of our physical weight being water, every human being needs to drink to stay healthy and fit. Pollution is threatening this vital life source for many countries. Particular nanostructures have an interesting promise to purify our waters.

Firstly, water purification membranes are typically divided into four categories according to pore size:

  • microfiltration (MF, < few microns)
  • ultrafiltration (UF, < 100 nm)
  • nanofiltration (NF, < 10 nm)
  • reverse osmosis (RO, < 1 nm)

Graphene Plus materials are effective at adsorbing organic pollutants such as hydrocarbons from water, soils and air. The first treatment project started in 2014. A Romanian former refinery site was to have its waster treated petroleum hydrocarbons. Approval was granted by the Italian Environmental Ministry for the use these products in oil spills clean-up activities.

Nanosurfaces may be functionalized and perhaps combined with other materials to create a nanoscavenger. For example, a nanofiber may be co-synthesized with  functional additives such as quaternary ammonium salt (QAS) biocides, polyoxometalates (POMs), fullerenes and phthalocyanines capable of neutralizing chemical and biological agents. Magnetism may also be used to recover the nanoscavengers and perhaps subsequently extract antibiotics, precious metals and other caught substances for subsequent use.

Zeolite layered and silica doped nickel ferrite magnetic cores have been found particularly useful to eliminate toxic ions of heavy metals such as lead and cadmium from polluted water.

Consumer

A Consumer Product Inventory has been spear-headed by the Virginia Tech Center for Sustainable Nanotechnology. Over 1,600 items are currently listed. Below are some highlights in how nanotechnology separates itself from traditional product designs and functions.

||Computing

Of the recent advances in nanotech, this section will describe already commercialized products. Toshiba has recently revealed its 19nm second generation NAND flash memory chips. The drives can accommodate storage from 4 to 128 GB (128Kbps transfer rate) in the conventionally small USB pocket flash-type size. Furthermore, IBM researchers announced in May 2014 that they have demonstrated a new record of 85.9 billion bits of data per square inch in areal data density on $0.02/GB linear magnetic particulate tape using barium ferrite (BaFe) particles.

||Coatings

Applying to cars, super hydrophobic coatings can reduce or eliminate the need to clean surfaces. Same could be done for fabrics, windows, wood, plastics, etc.

 

||Interior decor

Nanoparticles are smaller than the wavelength of light. This feature alone provides the possibility of special photonic phenomenon to occur. The result is controllable variation and longevity of color. Nano TiO2 is already widely used in paints for its whitish look.

||Personal protection

Sunscreen is a prime example of nanotech-enabled consumer products. Tonnes of TiO2 are being produced to add into the sun block formula. TiO2 in general is an opaque to UV rays. It is also a white pigment, but used in small quantities such as nanoparticles will still leave the skin with no white marks.

||Sports equipment

Offering a material improvement in terms of strength and weight, some nanostructures have found their way into fishing rods.

Biology

||Bio-markers

One of the most versatile and affordable methods available, bio-markers use fluorescent response of tagged molecules of interest. The key is to use an array of fluorescent tags which collectively provide enough information to identify a molecule of interest. HIV, syphilis and other infectious diseases may be tested by the mChip.

 

||Cells and nanomedicine

Human cells constantly interact with their surroundings: up-taking, releasing, communicating, defending etc. Introducing nanostructures into the picture provides a more comprehensive understanding of our health. Au fractal nanostructures that mimic the surfaces of cancer cells are found to attract the cancer cells with excellent specificity. Moreover, controlled release of the cancer cells with a viability of ca. 95% is possible by electrochemical bond cleavage for subsequent assessment and screening.

Magnetic NPs (e.g. iron oxide), could be functionalized to be drawn into a cell surface receptor. At this point, a magnetic field is applied to destroy the cell. Several mechanisms may be possible, of which apoptosis (programmed cell death) seems to be likely as the lyposome become permeabilized. Cell heating and NP rapid rotation may also contribute disrupt the lysosomal membrane. Magnetic NPs may also be embedded into a nanofiber mesh to reduce their diffusion and possible side effects. They may also be coated with nontoxic polymer polyethylene glycol and assist in the delivery of mesenchymal stem cells.

Au NPs are also effective therapy agents. Cationic Au NPs of 2 nm diameter could be delivered to and pass straight through the lipid membrane and embed themselves deeply within the floating bilayer, destabilising the entire membrane structure sufficiently to completely destroy the cell. NP penetration thus also facilitates improvements in photodynamic therapy that may be activated by ultraviolet, visible, and most recently infrared light. In contrast, anionic NPs do not penetrate the lipid membrane.

However, the shape of the NPs is also non-trivial. For example, nanorods with a higher aspect ratio adhere more effectively to endothelial cells that line the inside of blood vessels.

||Heart

Some cells in our bodies will not be automatically replaced or repaired. This is considered to be true for our heart. As with bone growth, there may be some way of improving the biosurface to enhance the ability of cardiomyocytes  (cardiac muscle cells) to attach, to proliferate, and secrete.

One solution is to use a hydrogel that is flexible enough to accommodate the stretching and contractions of the heart. The hydrogel may also be doped with CNTs to make it more conductive. This will provide a better synchronization and faster acceptance of a synthetic material within the heart. Gold coated  polycaprolactone–gelatin nanofibers can also enhance signaling.

||Nano robots

This is what it was all about. A robot that can automatically cruise our blood stream and keep us healthy. In one example, nano robots may act as an anti-tetanus agent to destruct the invasive C.tetani bacteria. Moreover, it can denaturize the arising TeTx toxin that may lead to severe muscular spasms and death.

 

||Volatile organic compounds (VOC)

Pre-clinical preparation for VOC analysis would require not to wear any perfume, deodorant or even antiperspirants. If fact, the smellier, the more airborne chemical molecules that may be detected. The scent of skin is used to differentiate melanoma cells (deadliest form of skin cancer) from normal cells. In this example, CNTs coated with strands of DNA act as an absorbent for subsequent gas chromatography-mass spectrometry analysis.

||Brain activity

Nematodes, also known as roundworms, are a variety of simple organisms with a worm-like appearance. With the help of one such nematode, called Caenorhabditis elegans, a new imaging technique was developed to monitor brain activity with both high temporal and spatial resolutions. The brain contains a network of neuron cells which process and transmit information. By inserting a fluorescent protein only into the nuclei of each neuron cell, sharper images of their activity are created. These images are scanned as one dimensional light discs by the WF-TeFo microscope and combined into a 3-D video of sculpted light which links brain anatomy to brain function.

at Open ND (TM)

Our flexible manufacturing technique that may be applied across a wide variety of materials makes a multitude of applications possible. We are currently developing solar energy harvesting technology, bio cell culture and scaffolding, MEMS, optical sensors, electronic bio-molecule sensors, micro-fluidics etc. Every applications brings new excitement and a greater opportunity to our developed expertise.