NovaCentrix JS-A426 Silver Nanoparticle Ink Enables Flexible Manufacturing of High-Performance Heat Flux Sensors
Accurate and high-resolution heat flux measurement is critical for optimizing the performance and understanding the complex thermal dynamics within demanding environments, such as internal combustion engines. These applications present significant challenges due to extreme temperatures, high pressures, and the need for sensors capable of responding to rapid transient events. Traditional measurement techniques often struggle with these conditions, necessitating innovative sensor designs and manufacturing processes.
A recent study published in the International Journal of Heat and Mass Transfer by Ghandhi et al. addresses these challenges through the rational design of an architected-wall surface temperature sensor. This research highlights the successful development and testing of sensors designed to enhance the signal-to-noise ratio for precise heat flux determination. Crucially, the study explored two distinct manufacturing approaches – lithographic patterning (LP) and aerosol jet printing (AJP) – with NovaCentrix conductive inks playing a pivotal role in enabling the advanced capabilities of these sensors.
Why High-Resolution Heat Flux Data Matters
The ability to accurately measure heat flux in real-time is fundamental to advancing the efficiency and durability of energy conversion devices. In internal combustion engines, for instance, understanding heat flow to the environment is key to minimizing energy losses and optimizing thermal management. The turbulent, high-temperature, and high-pressure conditions within an engine cylinder demand sensors that are not only robust but also possess high temporal and spatial resolution to capture the intricate, transient heat transfer phenomena.
This paper demonstrates a sensor design that significantly improves the signal strength of temperature measurements, thereby enhancing the accuracy of derived heat flux data. By comparing lithographic and aerosol jet printing, the researchers also provide valuable insights into scalable and flexible manufacturing routes for these critical devices, moving beyond the limitations of conventional fabrication methods.
The Role of NovaCentrix Conductive Inks
NovaCentrix conductive inks were instrumental in the fabrication of the advanced sensors described in this research, particularly in demonstrating the versatility and advantages of aerosol jet printing. The study utilized two specific NovaCentrix silver nanoparticle inks:
- NovaCentrix JS-A426 Silver Nanoparticle Ink: This ink was central to the aerosol jet printing (AJP) process. Researchers employed an Optomec AJ200 aerosol jet printer to aerosolize the JS-A426 silver nano-particle ink, depositing it to form the thin-film resistance temperature detector (RTD) sensing elements. The AJP method, enabled by JS-A426, offered significant benefits over lithography, including greater flexibility in sensor design, less complex manufacturing, faster processing, and increased tolerance for surface imperfections. The deposited lines were approximately 20 µm wide, and the silver ink was subsequently sintered at 270°C for one hour in a vacuum oven to achieve high conductivity.
- NovaCentrix SPI-502GL Silver Nanoparticle Conductive Ink: For the lithographically patterned (LP) sensors, SPI-502GL silver nanoparticle conductive ink was airbrushed over the feed-throughs. This application ensured robust electrical contact across the relatively large (12.5 µm) step caused by the end mill, which was necessary to connect the thin (100 nm) sensing element to the external electronics. This ink was also sintered at 270°C for one hour.
The successful integration of these inks underscores NovaCentrix’s commitment to providing high-performance materials that facilitate cutting-edge research and development in printed electronics.
Architected-Wall Sensor Design and Performance
The core innovation of the sensor design lies in the inclusion of an engineered, electrically and thermally insulating layer, specifically 12.5 µm thick Parylene HT, which separates the temperature-sensing element from the metal substrate. This layer is crucial because it amplifies the temperature swing experienced by the sensing element, effectively increasing the signal level without introducing additional noise. The study demonstrated that a coated sensor experienced a temperature swing 54 times greater than a bare aluminum surface when subjected to the same heat flux, significantly boosting the signal-to-noise ratio.
Both the lithographically patterned (LP) and aerosol jet printed (AJP) sensors were rigorously tested in a shock tube and in motoring internal combustion engines. The results showed that both manufacturing processes yielded sensors with comparable performance in determining heat flux. Despite the AJP sensor having slightly lower signal-to-noise ratio in some engine tests (due to the experimental setup matching Joule heating rather than signal level), the mean heat flux data from both sensor types matched exceptionally well across various engine operating conditions. The sensors were capable of resolving single-cycle heat flux and intra-cycle turbulent fluctuations, providing invaluable data for engine analysis.
Enabling Flexible Manufacturing for Advanced Sensor Applications
A key takeaway from this research is the validation of aerosol jet printing as a viable and advantageous manufacturing method for these sophisticated sensors. The AJP process, utilizing NovaCentrix JS-A426 ink, was found to be significantly less complicated, faster, and more forgiving of surface imperfections compared to lithography. This flexibility means that architected-wall sensors can be more readily fabricated on non-planar surfaces and integrated into complex geometries, expanding their potential applications beyond the laboratory.
The ability to achieve comparable high-quality heat flux measurements with a more versatile manufacturing technique like aerosol jet printing opens new avenues for the widespread adoption of these advanced sensors. This is particularly important for applications where cost-effectiveness, rapid prototyping, and adaptability to diverse form factors are crucial.
Looking Ahead: Impact of Advanced Conductive Materials
This study powerfully illustrates how the rational design of sensor architectures, combined with advanced conductive materials and flexible manufacturing techniques, can lead to significant breakthroughs in measurement technology. NovaCentrix is proud to contribute to such innovative research by providing the high-performance inks that enable these next-generation devices.
As industries continue to push the boundaries of performance and efficiency, the demand for precise, robust, and adaptable sensing solutions will only grow. NovaCentrix remains committed to supporting researchers and developers with materials that not only meet these stringent requirements but also unlock new possibilities for printed electronics in critical applications worldwide.