Manufacturing Ideas to Watch – Issue 15 (July 2018)

In this issue of Manufacturing Ideas to Watch: Intellectual Property Theft, Wireless Force Sensors, Thermochromic Polymers, New Solar Cell Material, and Environmentally Adaptive Fabrics. Let us know what you think by leaving a comment!

Intellectual Property Theft Using Acoustics of Additive Manufacturing

Diagram of intellectual property theft via acoustics
Image Source: Research paper, Figure 4

Additive manufacturing is increasingly being used to produce parts that involve sensitive intellectual property (IP). Accelerating implementation and innovation in additive manufacturing relies on understanding how this valuable IP is vulnerable and devising systems to protect it. Researchers at University of California, Irvine discovered that acoustics can be used to perform a side channel attack. In this attack, acoustic information is gathered from the additive manufacturing system, captured from the sounds created by the stepper motors that drive the internal components. The G-code, containing information about the movement and speed of the deposition head, can then be reconstructed from this acoustic information. Finally, the G-code can be used to reconstruct the underlying design and steal the intellectual property. This has been demonstrated on fuse deposition manufacturing systems, demonstrating the critical need to discover and implement protections for additive manufacturing systems.
Mohammad Al Faruque, University of California, Irvine

Wireless Force Sensors Improve Robotic Milling Accuracy

Diagram of wireless sensor application
Image Source: Research paper, Figure 3

Robotic milling machines reduce capital investment costs and equipment footprints while improving flexibility and versatility, as compared to traditional multi-axis machining centers. However, robotic milling can only provide limited accuracy. Researchers at Georgia Tech demonstrated that in situ wireless force sensors can be used to measure milling forces in real-time, providing opportunities for real-time tool position correction and ultimately improving accuracy. Using a model of the mechanics of the robotic milling machine, a closed-loop controller provides corrective feedback to the robot’s controller, allowing for greater than 70% improvement in the dimensional accuracy. This technology holds promise for large area, low-cost, multi-axis machining.
Shreyes N. Melkote, Georgia Tech

Thermochromic Polymers for Early Detection of Thermal Damage in Composites

Chart of film sensors
Image Source: Research article, part of Figure 7

Early detection of damage to carbon fiber-epoxy composites is crucial for ensuring safety in critical applications, such as aerospace components. Thermal damage detection is especially difficult as it presents as chemical, rather than mechanical degradation. Existing ultrasonic non-destructive testing methods are not able to detect this damage until it has progressed to later-stage cracks and delamination. Researchers have developed a thermochromic polymer that changes both color and fluorescent intensity when exposed to specified temperature-time combinations. These time-temperature combinations can be tuned to match the conditions that cause damage to composites. When applied as either a large area sheet or as a small sensor, this material provides easy visual detection of early-stage thermal damage. This technology has applications in vehicles, passenger aircraft, and renewable energy sectors as they transition to ubiquitous use of composites.
Ryan Toivola, University of Washington

New Solar Cell Material for Mass Adoption

Photo of solar cells at sunset
Image Source: Press release

Silicon-based solar cells max out in efficiency at about 20%. Higher efficiency requires silicon alternatives, but the best performing ones tend to be rare or toxic, limiting massive, large scale adoption. For example, gallium arsenide can provide an efficiency of 46%, but gallium is rarer than gold and arsenic is toxic. Prof. Pierre Ferdinand Poudeu of the University of Michigan Material Science and Engineering Department, has been investigating alternative solar cell materials that provide high efficiencies while also being safe, abundant, and inexpensive. His team discovered a promising candidate made of copper, titanium, and selenium (Cu4TiSe4). In addition to being nontoxic and from abundant elements, the fabrication process, based on powder and pulse laser deposition, uses less materials and is cheaper than molecular beam epitaxy used for GaAs films. The absorption coefficient of the new material in wavelengths of peak solar irradiation are 5 to 10 times greater than established high-efficiency photovoltaic materials, suggesting that one day it could exceed current efficiency records.
Pierre Ferdinand P. Poudeu, University of Michigan

Environmentally Adaptive Fabrics

Photo of adaptive fabric
Image Source: Blog post

Researchers at Otherlab produced a cloth that alters its ability to insulate as temperature changes. The cloth is made of two readily available polymer fibers with different coefficients of thermal expansion. The fibers are woven to behave as bimorph actuators: when cooled, one fiber shrinks more than the other such that it pulls on the fabric and change the shape of the cloth. In this case, the cloth deforms with decreasing temperature to become thicker and trap more air within it (air is a good thermal insulator). Experimentally, this fabric doubles its thermal resistance when the temperature drops from 81°F to 63°F, meaning it could keep someone wearing this cloth as warm as if she was to put on another layer of clothing. A different configuration would similarly keep a person cool when suddenly exposed to heat. In addition to applications in advanced apparel, such as gear for outdoors and first responders, clothing made with adaptive thermal insulation could be particularly useful to manufacturing workers that intermittently expose part of their bodies to extreme heat, such as steel mill operators and welders, by offering gear that is comfortable to wear all the time and is also heat-protective when needed.


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