CityU Research on Materials, Nanotechnology, Perovskite Solar Cells and Droplet Electricity

City University of Hong Kong (CityUHK) comprehensive information database · 04 Research module This article focuses on the fields where CityU has its highest concentration of Highly Cited Researchers and its strongest output in the Nature Index and patents — materials science, nanomaterials, mechanical engineering, and electrical/electronic engineering — and traces several landmark breakthroughs (perovskite solar cells, dual-phase nanostructured metals, phase-engineered nanomaterials, terahertz/millimetre-wave technology) with full sourcing. Four deeper dives have their own dedicated articles: High-Entropy Alloys and Advanced Metallurgy, Zhang Hua and Phase-Engineered Nanomaterials, Perovskite Solar Cells, and Wang Zuankai and the Droplet Electricity Generator. Platform institutions (SKLTMW, NPMM, CASM) are covered in institutes-and-labs.md; the full list of Highly Cited Researchers appears in named-centres-and-honours.md; patent commercialisation is covered in output-and-startups.md.

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If you had to explain to an outsider, in a single table, what CityU's research is "good at", the materials science column would be the one in bold. In 2024, the leading materials journal Advanced Materials devoted a special issue to CityU, with a title bordering on the self-congratulatory — "Three Decades of Materials Research Excellence at CityU". For a university barely forty years old and smaller than most of its Hong Kong peers, persuading a top journal in the field to devote an entire issue to reviewing its "thirty years of excellence in materials research" is, in itself, recognition from the research community.

# 1. Why Materials/Engineering Is CityU's Signature

Break CityU's research output down, and materials science and engineering emerges as the core engine of its international visibility:

• Concentration of Highly Cited Researchers: of CityU's 32 Clarivate Highly Cited Researchers in 2025^※, a substantial share work in materials science, chemistry and nanomaterials (individual listings in named-centres-and-honours.md).
• 30th-anniversary special issue endorsement: in 2024, the year CityU marked its 30th anniversary under its current name, Advanced Materials published a special issue, "Three Decades of Materials Research Excellence at CityU"^※, systematically reviewing three decades of CityU materials research — a public acknowledgement of its standing in the field.
• Platform support: the State Key Laboratory of Terahertz and Millimeter Waves (SKLTMW), the Hong Kong Branch of the National Engineering Research Center for Precious Metals (NPMM), and the Centre for Advanced Structural Materials (CASM) all sit in the materials/engineering space (see institutes-and-labs.md).

The representative breakthroughs below are organised along four lines: energy materials → structural materials → nanoscience → electronic/electromagnetic engineering.

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# 2. Landmark Breakthrough (1): Solving the "Thermal Stability" Problem in Perovskite Solar Cells

Narrative (based on CityU press releases and the Science paper). Perovskite solar cells are known for high power-conversion efficiency but have long been dogged by thermal instability, which has hindered commercialisation. According to a CityU press release (20 October 2023)^※, a team led by Professor Zhu Zonglong of the Department of Chemistry designed a self-assembled monolayer (SAM) and anchored it to the surface of nickel oxide nanoparticles as a hole-extraction layer, markedly improving device thermal stability.

According to the report, the improved devices retained over 90% of their efficiency after more than 1,000 hours of continuous operation at around 65°C, achieving a conversion efficiency of 25.6%. The work was published in Science as "Stabilized hole-selective layer for high-performance inverted p-i-n perovskite solar cells", a collaboration between CityU and Professor Li Zhongan of Huazhong University of Science and Technology (per the CityU press release (20 October 2023)^※). Further detail on this research line — including two earlier breakthroughs in interface engineering and non-volatile additives, and the collaboration with the US National Renewable Energy Laboratory (NREL) to overcome the mass-production bottleneck — appears in the dedicated article Perovskite Solar Cells.

This work represents CityU's "energy materials" direction: it answers a global and national demand for clean energy while fitting the University's own Hong Kong Institute for Clean Energy (HKICE) strategy (see institutes-and-labs.md).

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# 3. Landmark Breakthrough (2): Dual-Phase Nanostructuring — Magnesium Alloys Nearing Theoretical Strength

Narrative (based on the Nature paper). The College of Engineering has a long track record in high-strength structural materials. According to a paper published in Nature (2017), "Dual-phase nanostructuring as a route to high-strength magnesium alloys"^※, the team proposed a dual-phase nanostructuring strategy: embedding sub-10-nanometre nanocrystallites in an amorphous glassy shell to produce a magnesium alloy film combining high strength with high deformability.

According to the paper and related CityU reporting, the resulting dual-phase material reached a strength of approximately 3.3 GPa — close to the ideal theoretical limit — about 10 times stronger than conventional crystalline magnesium alloys, with super-deformability roughly double that of magnesium-based metallic glass. Because magnesium is biodegradable, the material has been flagged as promising for biodegradable medical implants (per the CityU research story (2017)^※).

The leading figure in this direction, Professor Jian Lu (Chair Professor of Mechanical Engineering, Dean of the College of Engineering, Senior Fellow of the Hong Kong Institute for Advanced Study), has an extensive publication record in experimental mechanics, residual stress and structural materials, with work frequently appearing in Nature, PNAS, Nature Communications and Science Advances (Lu's academic honours are listed in named-centres-and-honours.md). This structural-materials line has produced a further series of breakthroughs in the more frontier branch of high-entropy alloys — from using cobalt to suppress nanoparticle coarsening to new mechanisms that break the strength–ductility trade-off — detailed in the dedicated article High-Entropy Alloys and Advanced Metallurgy.

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# 4. Landmark Breakthrough (3): Phase Engineering of Nanomaterials (PEN)

Narrative (based on CityU research story pages). Professor Zhang Hua of the Department of Chemistry (Herman Hu Chair Professor of Nanomaterials) proposed and systematised the concept of "Phase Engineering of Nanomaterials (PEN)" — treating phase as a structural parameter on a par with composition, morphology, size and dimensionality, and designing the properties and functions of nanomaterials by tuning their phase (per the CityU research story (21 May 2020)^※).

At the heart of PEN is the preparation of metals and two-dimensional (2D) nanomaterials with unconventional phases, and the epitaxial growth of heterostructures to serve a range of applications. Zhang is among the most highly cited scholars in materials/chemistry and has long been named a Clarivate Highly Cited Researcher (see named-centres-and-honours.md); PEN has become one of CityU's signature concepts in nanoscience on the international stage. The full arc of the concept — from the first synthesis of hcp-phase gold nanosquares via graphene oxide templating to its institutionalisation as the theme of the Nature Conference on Phase Engineering of Nanomaterials 2024 — is traced in the dedicated article Zhang Hua and Phase Engineering of 2D Nanomaterials.

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# 5. Electronic/Electromagnetic Engineering: Terahertz, Millimetre Waves and 6G

In electrical/electronic engineering, CityU's flagship is the State Key Laboratory of Terahertz and Millimeter Waves (SKLTMW) — Hong Kong's first state key laboratory in engineering, approved by the Ministry of Science and Technology in March 2008 (see institutes-and-labs.md). Its core directions include:

• Antenna design (including high-performance antennas for millimetre-wave and terahertz bands);
• Radio-frequency integrated circuit (RFIC) design;
• Fast computational electromagnetics;
• Frontier applications in 6G communications, terahertz imaging and spectroscopy.

This line unites CityU's research in wireless communications, electromagnetics and integrated circuits under one national-level platform, and is a major source of its engineering-related US patents (patents in output-and-startups.md).

Metasurface antennas: software-defined "universal" antennas for 6G. A development by the team of Professor Chan Chi-hou, Head of the Department of Electrical Engineering, moves this research line from "laboratory metrics" to "programmable communications hardware". According to a CityU press release (16 December 2024)^※, the team, in collaboration with Southeast University in Nanjing, developed a metasurface antenna, described in the paper "A synthetic moving-envelope metasurface antenna for independent control of arbitrary harmonic orders", published in Nature Communications. Using a 1-bit coding strategy, the antenna generates and independently controls multiple harmonic frequency components simultaneously in software — effectively achieving with a single piece of hardware what previously required multiple systems. The team says it could be used in next-generation high-capacity, high-security information systems, real-time imaging, wireless power transfer, and integrated sensing and communication (ISAC), one of the key technologies for 6G. The work was supported by the Hong Kong Research Grants Council and the Shenzhen Natural Science Fund (per the same press release).

From the laboratory to a 600-metre mine: SKLTMW's application outlet. In 2026, SKLTMW's 6G research acquired its first concrete "underground" application scenario. According to a CityU press release (2 July 2026)^※, the laboratory signed a cooperation agreement with the China Coal Technology & Engineering Group (CCTEG) to conduct field surveys in a 600-metre-deep underground mine, exploring the application of 6G communications and intelligent technologies to coal-mine safety — continuing the direction set by the two parties' exchange and agreement in April 2026^※. Signal propagation in underground environments, underground positioning and intelligent monitoring are among the few real-world deep-mine test cases of terahertz/millimetre-wave technology in civilian industrial settings.

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# 6. Mechanical Engineering and Advanced Manufacturing: From Aircraft Skins to Electricity from a Raindrop

Beyond structural materials, CityU's mechanical engineering has output in additive manufacturing (3D/4D printing), metallic glass, advanced alloys and biomimetic surfaces. CityU teams have published review work on scientific advances in 2D/3D/4D additive manufacturing^※. Much of this work is carried out in coordination with platforms such as NPMM and CASM (see institutes-and-labs.md).

A fatigue-resistant aluminium alloy: strength that aircraft engine fan blades can use. The "structural materials" and "additive manufacturing" lines converge in this achievement. According to a CityU research story (24 October 2023)^※, a team led by Professor Jian Lu, together with CityU's Professor Wang Haowei and a team led by Professor Chen Zhe of Shanghai Jiao Tong University, used Laser Powder Bed Fusion (LPBF) to decorate nanoscale TiB₂ particles into AlSi10Mg aluminium alloy powder, producing a new alloy named NTD-Al. According to the report, its fatigue strength reaches 260 MPa, roughly double the fatigue resistance of comparable 3D-printed aluminium alloys — surpassing even traditionally forged high-strength aluminium alloys. The paper, "Achieving ultrahigh fatigue resistance in AlSi10Mg alloy by additive manufacturing", was published in Nature Materials and featured in Science's "Research Highlights" section, which described it as a general strategy for fatigue resistance that could be extended to other alloy systems. The alloy has already been used to fabricate large thin-walled structural components such as aircraft engine fan blades, and prototype certification testing has been completed (per the same report). This work comes from the same leading figure as the dual-phase magnesium alloy, echoing Professor Lu's long-standing track record in structural materials described in Section 3, and shares its alloy-design logic with the High-Entropy Alloys and Advanced Metallurgy article.

Also under mechanical engineering, but taking a very different path — biomimetic surface science. The team of Professor Wang Zuankai, Chair Professor in the Department of Mechanical Engineering, started from the water-repellent principle of lotus leaves and progressed to a 2020 Nature cover-level result: a single drop of water falling from a height of 15 centimetres, passing through their field-effect-transistor-style droplet electricity generator, instantly lit 100 small LED bulbs. This research line — from "superhydrophobicity" to "electricity generation" to the "266-year Leidenfrost puzzle" — is covered in the dedicated article Wang Zuankai and the Droplet Electricity Generator.

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# 7. Material Miracles at Extreme Scales: Stretchable Diamond and Origami Ceramics

Materials science has a common intuition: the harder, the more brittle. Two pieces of CityU work directly challenge that intuition — making "brittle" materials "tough", not by changing the recipe but by changing the scale.

Nanodiamond: a "brittle" material that stretches 9% without breaking. Diamond is one of the hardest natural materials, yet bulk diamond has almost no capacity for elastic deformation — a slight pull and it fractures. According to a paper published in Science (2018), "Ultralarge elastic deformation of nanoscale diamond"^※, an international team led by CityU used a plasma etching process to shape diamond films deposited on silicon substrates into needle-like single-crystal and polycrystalline structures on the order of 300 nanometres. According to the paper, single-crystal diamond needles recovered fully reversibly at a maximum tensile strain of about 9% — near the theoretical elastic limit — with a corresponding maximum tensile stress of approximately 89 to 98 gigapascals (GPa). The researchers attribute this "nearly unbreakable" stretching to the scarcity of defects and the relatively smooth surfaces at the nanoscale, and suggest the finding could find use in nanotechnology, biomedicine and even quantum information technology — for example, diamond-needle-based drug delivery into cells.

4D-printed ceramics: ceramic precursors that fold like origami. Ceramics are likewise known for being hard and brittle, and conventional 3D printing struggles to produce complex-shaped ceramic parts directly. According to an official CityU report (30 August 2018)^※, a CityU team developed a "ceramic ink" made from a mixture of polymer and ceramic nanoparticles. The 3D-printed ceramic precursors from this ink are soft and stretchable — stretchable to more than three times their original length without breaking — allowing them to be folded into complex configurations resembling origami, before being programmatically released and self-shaped into rigid ceramic structures. The work, published as "Origami and 4D printing of elastomer-derived ceramic structures" in Science Advances, has been described as the world's first "4D printing of ceramics". Along with the fatigue-resistant aluminium alloy, this work extends CityU's additive-manufacturing thread of "opening a flexible processing window for brittle materials", and echoes the overall character of CityU materials science as described in Section 1: "heavy platforms, dense breakthroughs".

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# 8. The Intersection of Materials and Optoelectronics: Biomimetic Neuromorphic Vision Sensors

Not all materials breakthroughs happen in structural or energy fields — the work of Professor Johnny Ho in the Department of Materials Science and Engineering plugs "materials design" directly into "perceptual computing", a track much closer to artificial intelligence.

According to a CityU research story (24 February 2025)^※ and a paper published in Nature Communications (2024), "Birdlike broadband neuromorphic visual sensor arrays for fusion imaging"^※, Ho's team, in collaboration with Central South University, constructed a van der Waals P3HT/GaAs nanowire P-N junction through directionally aligned organic molecules, combined with a Schottky junction, to create a wearable biomimetic sensor that mimics bird vision. According to the paper's abstract, the device achieved broadband non-volatile memory, weak-light sensing and near-zero power operation in both single-device and 5×5 array configurations, with more than 5 bits of in-memory sensing-computing capability; combining visible-light and ultraviolet imaging modes, its reservoir-computing system reached an accuracy of up to 94% in colour recognition. The team notes the device holds application potential in autonomous driving, robotics and advanced vision devices (per the same paper). This work was named among "Hong Kong's Top Ten Innovation and Technology News for 2025"^※, making it the second Department of Materials Science achievement to be included in the annual Hong Kong innovation and technology selection, after Zhang Hua's "Phase Engineering of Nanomaterials" — for the department's faculty and further academician honours, see faculty-and-leaders.md and academicians-and-awards.md.

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