Why do we need flexible electronics?

For multitude of reasons. Take a look at the mechanical compliance of various materials (right). It clearly shows the most prominent electronic materials are not physically compatible with the irregular surfaces, non-uniform body contour, etc., that exists in nature. 

Next, to know and to interact with nature more intimately flexible (physically compliant) electronics will be the key.

Finally, we believe stylistically this is just awesome!

Why most researchers explore alternate materials rather than crystalline material like Si/SiGe/Ge/III-V?

Because 0D organic/molecular materials, 1D nanowires, rods, tubes, 2D atomic crystal structure materials are often naturally flexible and stretchable. But they have some fundamental challenges to overcome. Electronics need to have higher information processing speed, energy efficiency, ultra-large-scale-integration (ULSI) density, reliability (manufacturing process, functionality, longevity) and cost-effectiveness. When we take all these factors into consideration, we clearly see benefits to "flex" and to "stretch" traditional crystalline materials like Si/SiGe/Ge/III-V.

INVITED REVIEW: According to US National Academy of Engineering (NAE) member, Prof. Mark Lundstrom of Purdue University (who is also the founder of nanohub), this paper clearly shows path forward for silicon CMOS electronics: "Repurposing Silicon Electronics"

Hussain, A. M. and Hussain, M. M. (2016), CMOS-Technology-Enabled Flexible and Stretchable Electronics for Internet of Everything Applications. Adv. Mater., 28: 4219–4249. doi:10.1002/adma.201504236 

Can we hybridize rigid ICs with naturally flexible alternate materials based devices? Aren't rigid ICs already very small?

Yes, that is the mainstream approach. Also, a common misconception is ICs are very small. We have thoroughly explained what are the fundamental issues about these approaches.

S. F. Shaikh, M. T. Ghoneim, G. A. Torres Sevilla, J. M. Nassar, A. M. Hussain, M. M. Hussain*, “Freeform Compliant CMOS Electronic Systems for Internet of Everything Applications”

Published in: IEEE Transactions on Electron Devices ( Volume: 64, Issue: 5, May 2017 ), Page(s): 1894 - 1905

DOI: 10.1109/TED.2016.2642340 

What are the approaches reported to flex silicon based electronics?

How can we flex traditional crystalline materials What are our approaches?

Ninety percent of the electronics today are made with bulk mono-crystalline silicon (100). And thus we have primarily focused on transform such electronics into flexible electronics. We have devised multiple CMOS compatible technologies to flex silicon CMOS electronics. They are chronicled in the following papers. Based on the needs and applications, one can choose any of them. They are highly cost effective too. 

How can we handle them? Like dicing, picking, placing, bonding, wiring.

By transforming the electronics into LEGO blocks. We curve interesting shapes with different size, height, angle on the back side of the "dies" and then on soft substrate (instead of PCB), we inkjet print interconnects (where resolution is acceptable), and make groove where such LEGO like electronics can fit easily (like self-assembly), eliminating need for further wire bonding. 

How can we package them?

It is a difficult challenge. Yet, we have been successful to develop highly reliable manufacturing process to combine complementary metal oxide semiconductor electronics, inkjet printing for interconnection, 3D printing for packaging, and roll-to-roll printing of decal electronics. The flexible electronic system shows reliable electrical performance, large-scale integration density as well as multifunctionality under extreme mechanical conditions. 

Sevilla, G. A. T., Cordero, M. D., Nassar, J. M., Hanna, A. N., Kutbee, A. T., Arevalo, A. and Hussain, M. M. (2017), 3D Printing: Decal Electronics: Printable Packaged with 3D Printing High-Performance Flexible CMOS Electronic Systems (Adv. Mater. Technol. 1/2017). Adv. Mater. Technol., 2: n/a. doi:10.1002/admt.201770002 

Have we built fully flexible electronic system?

Yes, including high performance circuitry.

Can we make 3D flexible silicon CMOS electronics What is Coin Electronics? Why such electronics are the only ideal solution for bioelectronics?

Yes. And that's critical for area preservation, enhanced performance and more importantly to remove the interface circuitry generated heat dissipation effect on natural skin, cells, etc. We are the only group who have demonstrated a completely CMOS compatible manufacturing process to use soft substrate as host medium and integrating sensors on one side and interface electronics on the other side like a coin (electronics). This can lead to ideal brain machine interface (BMI).

The fabrication is done monolithically in a single process-flow, following which the polymer is released to obtain a flexible device with sensors on one side and control electronics on another, interconnected using through polymer vias (TPVs). The TPVs are formed using copper embedded in thin polyimide structure for support. The copper interconnects offer a stable impedance frequency response from DC to 100 kHz (Z ≈ 20 Ω, θ ≈ 0°). 

Hussain, A. M. and Hussain, M. M. (2016), Deterministic Integration of Out-of-Plane Sensor Arrays for Flexible Electronic Applications. Small, 12: 5141–5145. doi:10.1002/smll.201600952 

Can we embed flexible CMOS electronics into complex objects?

Yes. Embedding high performance flexible solid state electronics in 3D printed flexible complex objects will enable a future where every single object made will be “live” (interactive). From a packaging perspective, 3D printing can tremendously enhance the device’s reliability and durability, while preserving its functionality. We have developed a hybrid approach to fuse 3D printing of flexible complex objects, CMOS compatible flexing of high performance solid state electronics, and robotic transfer printing of those flexible electronics (CMOS and optoelectronics) to embed them into the 3D printed flexible complex objects. As examples, we show fully functional complex architectures, such as: the KAUST Beacon in the Red Sea with light emitting diodes. The key enabler for this process is carefully orchestrated temporal and spatial control, through robotic placement of flexed electronics using a stop-gap measure in 3D printing and interconnecting. We believe integration of next generation electronics with 3D printed flexible complex objects can enable “internet of everything” applications – advancing the general area of healthcare, robotics and a smart world.

Is there an environmentally benign way to dispose flexible electronics?

Yes. We are the first lab who have shown using water only, germanium oxide gate dielectric or insulating layer can be removed quickly to dispose non-usable materials in environmentally benign way, as well as, to recycle expensive substrates.

A. S. Almuslem, A. N. Hanna, T. Yapici, N. Wehbe, E. M. Diallo, A. T. Kutbee, R. R. Bahabry, M. M. Hussain*, “Water Soluble Nano-scale Transient Material Germanium Oxide For Zero Toxic Waste Based Environmentally Benign Nano-Manufacturing”, Appl. Phys. Lett. 110, 074103 (2017)