Research Bits: Oct. 22

3D-printed active electronics

Researchers from MIT demonstrated fully 3D-printed semiconductor-free resettable fuses.

Produced using standard 3D printing hardware and an inexpensive, biodegradable polymer filament doped with copper nanoparticles, the device can perform the same switching functions as the semiconductor-based transistors used for processing operations in active electronics. After 4,000 cycles of switching, the devices showed no signs of deterioration.

While they don’t match the performance or small size of semiconductor transistors, the team said the 3D-printed devices could be used for basic control operations like regulating the speed of an electric motor.

The devices are made from thin, 3D-printed traces of the copper-doped polymer. They contain intersecting conductive regions that enable the researchers to regulate the resistance by controlling the voltage fed into the switch. (Credit: Image courtesy of the researchers / MIT)

“This technology has real legs. While we cannot compete with silicon as a semiconductor, our idea is not to necessarily replace what is existing, but to push 3D printing technology into uncharted territory. In a nutshell, this is really about democratizing technology. This could allow anyone to create smart hardware far from traditional manufacturing centers,” said Luis Fernando Velásquez-García, a principal research scientist in MIT’s Microsystems Technology Laboratories. “The reality is that there are many engineering situations that don’t require the best chips. At the end of the day, all you care about is whether your device can do the task. This technology is able to satisfy a constraint like that.”

The researchers plan to further develop the technology to print fully functional electronics and aim to fabricate a working magnetic motor using only extrusion 3D printing. [1]

Edible toothpaste-based transistor

Researchers from the Istituto Italiano di Tecnologia and University of Novi Sad designed an edible toothpaste-based transistor that could be used in applications like smart pills.

The devices are made with copper phthalocyanine, a food-grade blue pigment that acts as a whitening agent in some toothpastes. The pigment’s chemical structure facilitates charge conduction within its crystals. The amount ingested while brushing one’s teeth would manufacture around 10,000 transistors.

In addition to the copper phthalocyanine, the researcher’s edible circuits used an ethylcellulose substrate, with electrical contacts printed using inkjet technology and a solution of gold particles, common in food decoration. A “gate” made from an electrolytic gel based on chitosan (a food-grade gelling agent derived from crustaceans) enables the transistor to operate at a low voltage of less than 1V.

The team intends to identify other edible substances with suitable chemical and physical properties to create an edible electronic device to use for healthcare applications, such as monitoring body parameters within the gastrointestinal tract. [2]

Solution deposition for large-scale electronics

Researchers from the University of Illinois Urbana-Champaign proposed a new solution deposition process for semiconductors that yields high-performing transistors by introducing more defects.

The team used solution deposition of the ordered defect compound semiconductor copper-indium-selenium (CuIn₅Se₈) to form high-speed logic circuits operating in megahertz with delay down to 75 nanoseconds. The process was also used to create transistors to drive a micro-display based on inorganic micro-LEDs with a resolution of 508 pixels per inch.

“It’s remarkable that even though there are more defects, their organization into ordered defect pairs are the reason our materials have the record-high performances for those made with solution deposition process,” said Qing Cao, associate professor of materials science & engineering in The Grainger College of Engineering, University of Illinois Urbana-Champaign. “We went further than fundamental materials science and showed that functional circuits and systems like displays can be constructed, paving the road toward their adoption in many emerging applications requiring high-performance electronics covering large areas.”

The material has a mobility 500 times greater than amorphous silicon semiconductors used in large LCD displays and four times greater than metal oxide semiconductors used in organic LED displays. The mobility is comparable to low-temperature polycrystalline silicon used in smartphone displays, without requiring the laser annealing step that limits display size. The researchers next intend to make the process more environmentally friendly. [3]

References

[1] Cañada, J., & Velásquez-García, L. F. (2024). Semiconductor-free, monolithically 3D-printed logic gates and resettable fuses. Virtual and Physical Prototyping, 19(1). https://doi.org/10.1080/17452759.2024.2404157

[2] E. Feltri, P. Mondelli, B. Petrović, F. M. Ferrarese, A. Sharova, G. Stojanović, A. Luzio, M. Caironi, A Fully Edible Transistor Based on a Toothpaste Pigment. Adv. Sci. 2024, 2404658. https://doi.org/10.1002/advs.202404658

[3] Hsien-Nung Wang et al., Solution-processable ordered defect compound semiconductors for high-performance electronics. Sci. Adv. 10, eadr8636 (2024). https://doi.org/10.1126/sciadv.adr8636