In the last two decades, there has been a rapid increase in the number of publications that focus on lab-on-a-chip systems. Researches from the Morin group lead by Prof. Stephen Morin, an Associate Professor at the Department of Chemistry, University of Nebraska leveraged from these systems in the realization of curvilinear printed circuit boards that have the potential to be the future of technology based on their numerous applications.
There is no doubt that advanced manufacturing techniques have enabled economical, large-scale and efficient manufacturing of different components including electrical circuit boards which are essential elements of modern-day consumer products. From simple toys to intricate systems, these electronic components have application in almost all industries. If the processor is considered as the brain of a device, then undoubtedly, circuits are the nerves that effect the overall function. And why not? They help power majority of the systems and give them direction. However, traditional component circuitry can only be used on a planar surface, and they are produced using top-down lithography. It’s only a matter of time when these components will no longer be used in devices for applications that require components to be non-flat or be flexible.
In a recent paper titled “Soft microreactors for the deposition of conductive metallic traces on planar, embossed, and curved surfaces” published in Advanced Functional Materials, Morin group at the University of Nebraska, demonstrated the seamless integration of microfluidics to produce circuits on non-planar objects and further attached various electronic components to these circuits. Leveraging the microfluidic technology with better standards of fabrication processes and facilities, the results showed promise of commercial standardization and up scalability to produce curvilinear printed circuit boards.
For those of you who are not familiar with the term “microfluidic device”, it is a configuration of components made from microscale fluid-like microchannels, chambers that allow easy flow of fluids and valves that are individually addressable. You might be wondering; this sounds a bit familiar, and you are correct. The description is fairly similar to an electric circuit where the only difference is the medium—in an electric circuit, there is a flow of electricity.
In a microfluidic device, the rate of fluid flow can be controlled, the direction of flow can be changed, chemical reactions can take place using a mixture of fluids, particles can be separated, etc. All this can happen in a single microfluidic device. Many experts consider microfluidic devices as using the model analogous to the electric circuit. With that out of the way, it is imperative to look at the research as mentioned above and how it benefits the future of electronics. The in-depth research was carried out by a highly qualified team of experts led by Prof. Stephen Morin, and included Dr. Abhiteja Konda, Prof. Christos Argyropoulos and others at the University of Nebraska, and was in part funded by the National Science Foundation (Grant No. 1555356) and the Nebraska Research Initiative.
These researchers have pulled off something unthinkable by developing a simpler and cost-effective method for depositing circuits on surfaces that are textured, stretchable and curved. The idea behind this technology is to free circuitry from the limitation of being rigid and flat on the circuit board. “If you can remove the need for dedicated substrates to house electronic circuits by coating support elements with those circuits, then you can save material and mass”, says Prof. Stephen Morin.
Unlike animals whose flexibility allows them to evolve through time taking different shapes, size and structure, the present-day circuit boards are rigid, flat and boxy devices. Morin and his team devised a technique called microfluidic-directed electroless copper deposition (μ-DECD)—a technique that can “paint” copper traces onto textured, non-planar, curved surfaces. This technology can transform nearly any kind of surface into a de facto circuit board with enhanced structural integrity and has the potential to revolutionize the electronics industry by saving the engineer valuable space and weight and expand the use of these structures into unprecedented domains.
According to Dr. Abhiteja Konda, currently a post-doc at the Argonne National Laboratory, and the lead author of this paper, “For the first time, we demonstrated the use of soft, microfluidic devices in the deposition of metallic traces. Our approach is unique in using simple process tools for the fabrication of circuits on non-planar, arbitrary surfaces.” Based on his experience, the technique is relatively simple, and would be able to offer better accessibility and affordability compared to the existing alternatives that use laser-based tools.
The μ-DECD process involved imprinting of the microscopic canals into an elastic material, which was then sealed by compressing onto various surfaces—a corrugated plane, a sphere or even a cylinder—anything that creates a reversible yet strong seal. The seal allowed the flow of solutions through the channels which were used for electroless deposition of copper. The metallic copper is deposited only in the areas exposed to the solutions as defined by the channels in the microfluidic device.
The team further demonstrated the use of these traces in producing a light-sensing circuit, and a radio frequency antenna that was used to transmit a signal and was detected using a smartphone through near-field communication.
Image Credit: University of Nebraska-Lincoln
Image Credit: University of Nebraska-Lincoln
Dr. Abhiteja Konda