Hydrogel NAND gate; long-distance remote epitaxy; PAM-8 receiver.
Researchers from McMaster University and the University of Pittsburgh created a functionally complete NAND gate in a soft material using only beams of visible light.
The NAND logic operation was completed by shining three self-trapped light beams into a photoresponsive merocyanine-functionalized hydrogel that is capable of performing compute tasks in the material itself without additional electronics. When a laser beam enters the gel, the local contraction increases the refractive index, causing the beam to “self-trap” – narrowing and brightening as it travels through the material.
“With three beams, we began to see consistent patterns of interaction that weren’t visible before,” said Fariha Mahmood, formerly a researcher at McMaster and now a postdoctoral researcher at the University of Cambridge, in a press release. “The middle beam is always dimmer because it’s fighting both of its neighbors. That reliable behavior is what lets us map a logic operation onto a soft material.”
While the system cannot compete with semiconductor processors in speed or data density, the researchers see potential in applications like soft robotics, medical devices, and inaccessible sensors.
“What excites me is the framework this establishes. We’re showing that computer logic – something we usually think of as the domain of electronics – can be carried out by a material through its own chemistry and physics. It’s a very different way of thinking about how materials can function,” added Kalaichelvi Saravanamuttu, professor of chemistry and chemical biology at McMaster, in a press release. “It’s exciting that just three beams of light and a polymer network can map directly onto a Boolean logic operation. You don’t need wires, electrodes, or external circuits. The material processes the inputs and determines the output entirely by its internal dynamics.”
Additionally, the team says the approach could allow multiple logic operations to occur simultaneously inside the same gel sample. [1]
Researchers from Rensselaer Polytechnic Institute, National High Magnetic Field Laboratory, Florida State University, and State University of New York at Buffalo discovered that remote epitaxy, in which a semiconducting film is grown on a substrate separated by a thin buffer layer before being peeled off and placed elsewhere, can be performed using a thicker buffer layer by taking advantage of substrate defects.
The substrate guides the film’s crystal growth, but buffer layers thicker than a nanometer can disrupt the electrostatic forces. Using a zinc oxide/gallium nitride model system, the team discovered that structural defects in the substrate could be deliberately engineered to control remote epitaxy processes, enabling long-distance electrostatic interactions that can influence the structure of the crystal layer. This allowed them to use carbon buffer layers up to 7 nanometers thick while growing crystal films that still aligned well with the substrate beneath.
“This work shows that remote epitaxy could be mediated by substrate defects such as dislocation,” said Jian Shi, a professor of materials science and engineering at RPI, in a statement. “Practically, that widens material choices, improves process windows, and aids scalable membrane release and wafer-recycling strategies in real devices.”
The researchers tested their approach with multiple crystal/substrate combinations. As a proof of concept, they built working photodetectors by transferring perovskite crystal films to flexible substrates. [2]
Researchers from Hanyang University designed a receiver frontend system for PAM-8 signal processing that enables data rates beyond 100 Gb/s. The design uses a multi-path architecture that doubles linearity with only a 20% increase in power.
The multi-path architecture enables each path to handle a sub-range of the total dynamic range, reducing the number of required slicers or samplers. To compensate for channel loss, the team implemented a separated feed-forward equalizer (FFE) path that allows it to calculate the compensation value using only a small, attenuated signal that fundamentally prevents compression, enabling successful channel loss compensation even while handling large input signals.
The team implemented the receiver frontend in 28nm CMOS, where it provided a data rate of 108 Gb/s and an input range of 1.4 Vppd with 210.8 mW total power and 1.95 pJ/bit efficiency. [3]
[1] F. Mahmood, V.V. Yashin, A.C. Balazs, et al. A functionally complete logic gate in a soft photoresponsive hydrogel. Nat Commun 16, 10006 (2025). https://doi.org/10.1038/s41467-025-64960-4
[2] R. Jia, Y. Xin, M. Potter, et al. Long-distance remote epitaxy. Nature 646, 584–591 (2025). https://doi.org/10.1038/s41586-025-09484-z
[3] S. Lee, H. Jo, H. Jeong, et al. A 108Gb/s PAM-8 CTLE+FFE Receiver Frontend with 1.4Vppd Input Range in 28nm. IEEE ASSCC 2025.
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