Manufacturing Bits: Jan. 22

Open-source CVD
Boise State University has developed an inexpensive chemical vapor deposition (CVD) system to enable the growth of two-dimensional (2D) materials.

Using open-source designs and off-the-shelf components, researchers have developed an automated CVD system for $30,000 in hardware costs, according to Boise State in the journal PLoS One.

2D materials could enable a new class of field-effect transistors (FETs) with some intriguing electrical properties. In 2004, graphene was the first 2D material isolated. Other 2D materials include boron nitride and the transition-metal dichalcogenides (TMDs). One TMD, molybdenum diselenide (MoS2), is gaining interest in the market.

CVD, a deposition method used to produce films or materials on structures, is a common system for the production of semiconductors. But generally, CVD systems are expensive and cost prohibitive for many research groups.

For R&D groups, there is a solution—open-source designs and components. Open-source designs are freely available and in the public domain.

Leveraging open-source designs and components, Boise State developed a four gas, variable pressure CVD system. “This system is capable of both atmospheric pressure and low-pressure growths, growth temperatures up to 1100 °C, and substrates up to ~20mm in width,” said Lizandra Williams and others from Boise State in the journal PLoS One. “Additionally, with the detailed parameter and recipe logging, past growths can quickly be audited for possible issues or repeated, allowing for quick system troubleshooting and high process repeatability. With the system described here, we have grown 2D materials such as graphene, WS2, as well as graphene/WS2 vertical heterostructures, with exceptional quality.”

Fabric deposition
The Imperial College London has developed a new metal deposition technique that can print metals onto natural fabrics.

Typically, the industry uses inks to print metals on paper and fabrics. These inks work, but they are expensive. For example, a gold-based inks sells for over $10 per gram, according to Imperial College.

In response, researchers from Imperial College have developed a process called SIAM or Si ink-enabled autocatalytic metallization. The technique can print silver, gold and platinum onto various fabrics.

In the flow, researchers first cover a fabric in microscopic silicon particles. Then, the fabric is submerged into a solution with metal ions. As a result, the ions move or are deposited on the silicon particles. This in turn allows metals to grow onto the material.

SIAM can be used for various applications. First, it can be used to print coil antennas on paper. Second, the technology can fabricate Ag–Zn batteries. Third, it could create electrochemical sensors, which in turn could detect nucleic acids and proteins.

“Fabrics are ubiquitous and some forms such as paper, are ancient. With this new method of metallizing fabrics, it will be possible to create new classes of advanced applications,” said Max Grell, a PhD candidate from Imperial. “We chose applications from a range of different areas to show how versatile and enabling this approach could be. It involved a lot of collaboration and we hope we have demonstrated the potential of this method so people who specialize in different areas can then develop these applications.

“The beauty of this approach is that it can also combine different technologies to serve a more complex application, for example low-cost sensors can be printed on paper that can then transmit the data they collect through contactless technology. This could be particularly useful in the developing world where diagnostic tests need to be conducted at the point of care, in remote locations and cheaply,” said Grell.

Old periodic table
The world’s oldest periodic table chart has been uncovered at the University of St. Andrews. The chart of elements was dated in 1885.

David O’Hagan, the former head of chemistry at the University of St. Andrews, said: “The discovery of the world’s oldest classroom periodic table at the University of St. Andrews is remarkable. The table will be available for research and display at the university and we have a number of events planned in 2019, which has been designated international year of the periodic table by the United Nations, to coincide with the 150th anniversary of the table’s creation by Dmitri Mendeleev.”

Dmitri Ivanovich Mendeleev, a Russian chemist and inventor, created a version of the periodic table of elements.