Aegle Technology

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Functional Inks

Bright future of Quantum dots!

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Quantum dots are nanoscale man-made semiconductor crystals (nanocrystals) that have the ability to convert a spectrum of light into different colours and have been gaining significant attention in recent years due to their unique properties and potential applications in a wide range of industries. This post aims to provide an overview of the market potential of quantum dots and their usage in various fields.

Quantum dots are nanostructures that can exhibit a wide range of properties. Due to their unique electronic characteristics, they can be utilized as active materials in single-electron transistors, for instance. The exhibited properties are determined not only by their size, but also by their material, shape, composition, and structure, such as whether they are solid or porous. It is a dependable manufacturing technology that exploits the properties of quantum dots for a variety of applications in fields such as catalysis, electronics, photonics, information storage, imaging, medicine, and sensing.

Due to the fact that certain biological molecules are capable of molecular recognition and self-assembly, nanocrystals have the potential to become an essential component of self-assembled functional nanodevices.In addition, the atom-like energy states of QDs contribute to their unique optical properties, such as a particle-size-dependent fluorescence wavelength; an effect utilized in the fabrication of optical probes for biological and medical imaging.

Each Quantum dot emits a different colour depending on its size. (Image: RNGS Reuters/Nanosys)

Market Potential of Quantum Dots

The value of the global quantum dots market was USD 4.4 billion in 2020 and is projected to reach USD 14.5 billion by 2027, expanding at a CAGR of 18.8% from 2021 to 2027 (depending on the source). This expansion can be attributed to the growing demand for quantum dots in the display industry, the largest application segment for quantum dots. Quantum dots offer numerous advantages over conventional display technologies, including a wider color gamut, enhanced color accuracy, and greater energy efficiency. In addition, the atom-like energy states of QDs contribute to their unique optical properties, such as a particle-size-dependent fluorescence wavelength; an effect utilized in the fabrication of optical probes for biological and medical imaging.

Apart from the display industry, quantum dots have a vast range of potential applications in other industries such as healthcare, energy, and security. In healthcare, quantum dots are being used in diagnostics, imaging, and drug delivery. Quantum dots have also shown potential in the field of solar cells, where they can improve the efficiency of solar cells by capturing a broader range of light. Additionally, quantum dots have been used in security applications such as authentication and anti-counterfeiting.

Usage Potential of Quantum Dots:

  1. Display Technology

As mentioned earlier, quantum dots offer significant advantages over traditional display technologies, such as liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs). Quantum dots enable displays to produce more accurate and vivid colors while consuming less energy. They are also resistant to degradation and provide longer lifespan to the displays.

  1. Healthcare

Quantum dots have shown potential in various healthcare applications such as diagnostics, imaging, and drug delivery.  When activated by light, quantum dots can emit specific wavelengths as fluorescent probes. This makes them sensitive and selective sensors for proteins, nucleic acids, and tiny compounds. Quantum dots can be functionalized with ligands or antibodies that preferentially attach to target biomolecules for immunoassays, DNA/RNA detection, and point-of-care testing. Their brightness, photostability, and multiplexing make them suitable for accurate and quick biomolecule detection, improving diagnostics and disease monitoring.

Quantum dots are promising contrast agents in fluorescence microscopy and MRI. Their brilliant and stable fluorescence can mark and track cells, tissues, or biomolecules in real time, revealing cellular activities, tissue architecture, and disease development. Quantum dots’ magnetic characteristics enhance contrast and imaging sensitivity in MRI. Quantum dots can be made with unique surface qualities to target specific tissues or cells for precise, non-invasive disease imaging.

Vials of quantum dots producing vivid colors. For instance, a cadmium-based quantum dot showing pure, highly specific green color response. (Image: NASA)

Drug delivery methods can increase efficacy and safety with quantum dots. Their small size, high surface area, and customizable surface characteristics make them suitable drug carriers. Quantum dots can be functionalized with targeting ligands that bind to receptors or biomolecules on target cells to selectively absorb and accumulate. Targeted medication administration reduces off-target effects and increases drug concentration at the site of action, improving therapeutic outcomes and lowering systemic toxicity. Quantum dots can also release medications slowly, prolonging their therapeutic effect.

  1. Energy

Quantum dots can improve the efficiency of solar cells by capturing a broader range of light.  Using quantum dots to manufacture solar cells has a number of advantages over alternative methods. They can be produced in an energy-saving room-temperature process from abundant, inexpensive materials that do not require extensive purification, unlike silicon, and they can be applied to a variety of inexpensive and even flexible substrate materials, such as lightweight plastics.

A promising method for quantum dot solar cells is the use of a semiconductor ink, which aims to enable the coating of large areas of solar cell substrates in a single deposition step, thereby eradicating the tens of deposition steps required by the previous layer-by-layer method. Although using quantum dots as the basis for solar cells is not a novel concept, attempts to create photovoltaic devices have not yet obtained a sufficiently high conversion efficiency of sunlight into electricity.

  1. Security

Anti-counterfeiting: Quantum dots in security inks or identifiers create distinctive, unforgeable patterns. Quantum dots emit light at specific wavelengths when stimulated by ultraviolet light, which can be used as a signature or barcode for authentication. Using specialized detectors, quantum dots can validate the authenticity of banknotes, passports, and other vital documents.

Quantum dots can be utilized as quantum light sources for secure communication. Quantum key distribution (QKD) uses quantum mechanics to create secure communication channels utilizing single photons from quantum dots. Due to their high quantum yield and wavelength-tunable emission, quantum dots hold promise for secure communications.

Quantum dots are tamper-evident labels that help secure shipments and merchandise. Quantum dots can be combined with inks or coatings that change color or emit light when tampered with, thereby indicating product or packaging corruption. This protects against forgery and manipulation.

Quantum dots can be used for fingerprint and iris recognition for biometric security. As fluorescent labels, quantum dots enhance the sensitivity and accuracy of biometric sensors. Quantum dots can detect unique DNA sequences in systems that rely on DNA for authentication.

Quantum cryptography: Using quantum physics, quantum dots can securely transmit cryptographic keys. Quantum cryptography devices use quantum dots as light sources or detectors to generate and detect quantum states for secure key exchange.

In conclusion,

quantum dots represent a cutting-edge technology that holds great promise for the future. With their unique properties and versatility, they offer a wide range of potential applications across various industries. From displays to lighting, to biomedical imaging, to solar cells and beyond, quantum dots are poised to revolutionize multiple sectors. Their ability to manipulate light at the nanoscale opens up new possibilities for enhanced performance and improved efficiency in existing technologies, while also paving the way for entirely new applications. As research and development in quantum dots continue to advance, the market potential for this technology is substantial.

Quantum dots are undoubtedly an attractive alternative to traditional technologies, and their vast usage potential is just beginning to be explored, making them a technology to watch in the coming years. The future of quantum dots is bright, and their impact on various industries is likely to be profound.

Aegle Technology – Nanoparticles for Printed Electronics

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Authors: Martí Busquets-Fité, Christopher W. Young

The field of printed electronics is advancing rapidly, changing the current paradigm of electronic devices and circuit boards from hard structures and rigid sheets to flexible thin layers, which will lead to the emergence of a plethora of new devices and technological possibilities such as disposable electronics, smart labels, and a further step in the ongoing process of miniaturization of devices. 

printed electronics

One of the main driving forces to achieve this is the development of nanoparticle-based “functional” inks.

Functional inks are used to create printed and flexible circuits and offer a cost-effective alternative to conventional methods such as etched copper flex circuits and printed circuit boards (PCBs). Functional inks make it possible for manufacturers to print on flexible substrates for mass-scale circuit manufacturing. Functional inks can be applied to a broad range of rigid and flexible surfaces using different printing processes:

  • screen printing (sheet-fed and roll-fed), 
  • aerosol jet printing, 
  • and gravure printing.

The choice of the printing technique depends on the ink type and ultimate product use. Functional inks are generally more environmentally friendly than traditional methods because etching copper on PCBs requires the use of acid baths, while the process of employing functional inks generates no waste and uses no harmful chemicals. 

Inks which conduct electricity have a wide range of uses, including:

  • capacitive and membrane switches, 
  • RFID tags, 
  • touch screens, 
  • biological and electrochemical sensors, 
  • Positive Temperature Coefficient (PTC) heaters, 
  • electromagnetic interference/radio frequency interference (EMI/RFI) shielding, 
  • wearable electronics (stretchy conductive inks).

The use of specific metal nanoparticles produced to tightly controlled specifications in the production of high-performance functional inks, such as required for printed electronics, helps to achieve the desired properties.

Nanoparticles (NPs) are usually defined as particles of matter that are between 1 and 100 nanometres (nm) in diameter. Because of their extremely small size (they cannot be seen even using an ordinary optical microscope) they exhibit very different physical and chemical properties, including the way they behave in a solution as well as optical effects and electric properties.

A wide variety of metals, including silver (Au), gold (Ag), platinum (Pt) and palladium (Pd), are used in nanoparticle form. 

Of all the metal nanoparticles, silver nanoparticles (AgNPs) possess the highest electrical and thermal conductivity which, along with other properties and factors (e.g., lower cost, resistance to oxidation, interesting plasmonic and antibacterial properties), has put silver nanoparticle (AgNP) based inks as the most widespread nanoparticles-based ink product with the better-established technology and the highest production and sales volumes. 

However, most of the currently available AgNP inks contain a remarkably broad distribution of sizes with specifications describing cut-off sizes rather than detailing mean sizes and size distribution. In practice, this reduces the effectiveness of these inks for many applications. 

Nanoparticles-based inks for printed electronics

Printed electronics requires inks with certain levels of viscosity and surface tension to be operable (achievable with the use of organic solvents, dispersing agents and humectants to avoid inks drying too quickly on the nozzles). Such general requirements depend on several factors: printing technique, requirements of the printing equipment and the desired functional properties of the ink as a final product. 

Of all the inks requirements, probably the most relevant and restrictive is their viscosity. For instance, aerosol jet printers can only operate with viscosities below 15 cP, piezoelectric printheads require viscosities between 5 and 20 cP and thermal printheads inks must have even lower viscosities (1-5 cP). 

Particle size is another restrictive requirement. For aerosol jet printers, particle size must be below 100nm to avoid clogging of the nozzles. That is why well-defined NPs below 100nm are clearly preferred for this technique and all printing techniques requiring an aerosolization step. 

Historically, noble metals (specially Au, Ag) and copper have monopolised the field of printed electronics, as are their nano-sized equivalents. Other materials such as nickel, brass, chromium, iron and iron oxides and even intrinsically conductive polymers and carbon-based materials have proved to yield to conductive nanotechnology-based inks and are worth mentioning, although attracting a significant lower deal of attention. 

In all the aforementioned cases, the nanoscale counterparts offer remarkable advantages in contrast to the bulk materials due to their scale: stable colloidal suspensions easy to manipulated and use in microfluidics and printing; high surface/volume ratio; collective electron resonances, the so-called plasma waves enabling surface plasmon resonance (SPR), and interactions with the electromagnetic field; a huge enhancement of diffusivity of the surface atoms; and above all, strikingly low sintering (melting) temperatures. 

Amongst all of them Ag possesses the highest electrical and thermal conductivity, which along with other properties and factors (e.g. lower cost than Au, Pt and Pd, resistance to oxidation, interesting plasmonic and antibacterial properties, etc.), has put the silver nanoparticles (AgNPs) based inks as the indisputable most widespread nanoparticles-based ink product with the better established technology and the highest production and sales volumes. 

3D Printing 

Apart from using nanotechnology-based conductive inks for printed electronics, other applications for inks based on NPs of different compositions are emerging. 

nanoparticle 3D printing

As already mentioned, AgNP inks (as well as AuNP and CuNP) used for printed electronics can be used for sensing, surface-enhanced Raman spectroscopy (SERS) and photonics, taking advantage of their unique electrical and optical properties. Nanoparticles-based inks are also being used in the thriving field of 3D printing.

Many promising materials have been developed, especially focused on metal oxides NPs with exceptional properties such as:

  • magnetic -including paramagnetic- inks (Fe3O4NPs); 
  • inks for printing intricate prosthesis and implants or other functional materials with antibacterial (with AgNPs), antifungal (with Cu2O, CuO and even Cu(0) NPs) and anti-inflammatory or pro-inflammatory (with the very promising CeO2NPs) properties; 
  • or the more complex hydrogels-based bioactive scaffolds that promote tissue growth around them (using “bio-inks” based on hydrogels including nano silicates).

Aegle Technology 

Aegle technology designs and manufactures a wide range of nanoparticles, including metal nanoparticle solutions (colloids) with highly uniform particle sizes (highly monodisperse) at distinctively high concentrations. Our AgNP colloids have a level of sphericity and mono-dispersity unmatched in the market, potentially providing superior and more robust electrical and physicochemical properties to inks (check our catalogue at https://aegle-technology.es/shop).

Specifically, our AgNP (and AuNP) colloids provide: 

  1. high morphological control and narrow size distribution 
  2. high colloidal stability (essential to avoid aggregation and clogging of the nozzles) 
  3. A range in sizes: 5, 20 and 50nm are our standard mean sizes but we can adapt to our clients preferred sizes – 60, 70, 80 , 90 or 100nm as mean size with <10% SD

We are experts in the design and production of NPs colloids for a broad range of applications, including for the formulation of functional inks. Our knowledge in this field comes from our direct experience interacting with clients in the conductive inks sector. 

Our experience includes different degrees of involvement in the preparation of the ink formulation:

  1. Supplying AgNP and AuNP colloids dispersed in aqueous media (2-5mM sodium citrate for concentrations up to 2mg Au/mL and + PVP of certain MWs and concentrations for concentrations as high as 50mg/mL) and our clients use them as core ingredients of their ink formulations. 
  2. Preparing highly concentrated inks following our client’s formulations using mixtures of water, ethanol and ethylene glycol, coupled with the use of dispersing and stabilizing agents such as PVP, methylcellulose, ethanolamine and other more specific dispersing agents. 

For more information, please see https://aegle-technology.es or contact us at sales@aegle-technology.es to discuss your requirements.