A single chip, smaller than a fingernail, could replace entire lab benches for sorting and identifying individual molecules. Today’s best porous materials, such as zeolites, have pores the size of small molecules but are difficult to integrate with electronics. Conversely, microchip fabrication cannot reliably create holes that small. This project bridges that gap by taking a top-down approach: peeling apart layered crystals into atom-thin sheets, then stacking them back together in precise sequences. The gaps between these sheets become slits just wide enough for single molecules to pass through. If successful, the result would be a “lab-on-a-chip” that combines sieving with electrical detection. A single device could separate a mixture of molecules and identify each one in real time, all on a microchip. This would shrink bulky chromatography equipment to portable size, with potential applications in medical diagnostics, water quality monitoring, or industrial process control. The work is fundamentally exploratory. The team must first measure how molecules behave when squeezed into atomic-scale slits—properties that differ sharply from those in bulk. Understanding these transport and structural characteristics is a necessary step before any practical device can be built.
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Our society heavily relies on various porous materials, which are used for filtration, gas separation, desalination, etc. As pore sizes become smaller and better defined, increasingly enhanced selectivity and performance characteristics can be achieved. While functional porous materials such as zeolites and metal-organic frameworks offer intrinsic molecule-size pores, they are hard to be integrated for nanoscale detection and characterization capabilities. Meanwhile, modern microfabrication techniques used to make integrated semiconducting circuits, have so far been unable to reliably create pores with size down to that of individual molecules. Here I propose a radically new top-down approach that allows nanofabrication of pores at the true atomic scale by assembling van der Waals (vdW) crystals in designer sequences. This involves disassembly of layered bulk crystals into individual atomically thin layers, followed by reassembly of these layers into artificial heterostructures. The proposed smart vdW sieving devices would combine molecular separation functions of well-defined nanopores with detection functions of modern chromatography. The whole device can be reduced in size to that of a tiny microchip. To realize such multifunctional compact wonder sieves, extensive work is first required to obtain electrical and optical characteristics of various molecules of interest confined inside atomic-scale slits, because structural and transport characteristics under strong confinement are expected to differ drastically from those in the bulk. In parallel, we will develop efficient molecular sieving through these vdW slits using a combination of steric and electrostatic exclusion. With such fundamental understanding of structural characteristics and transport mechanisms at the molecular scale, my team and I will demonstrate smart integrated sieves (lab-on-a-chip technology at atomic-scale) for simultaneous separation and detection of various molecules.
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