Research Highlight

Multimodal Dynamic and Unclonable Anticounterfeiting Using Robust Diamond Microparticles on Heterogeneous Substrate

Counterfeiting is a global menace endangering financial security, national safety, and public health. Traditional methods like watermarks and QR codes are vulnerable due to deterministic fabrication. Unbreakable security labels with physical unclonable functions (PUFs) offer a promising solution. PUFs leverage inherent randomness to create unique identifiers like fingerprints. Here, diamond-based PUFs, utilizing the stochastic nature of artificial diamond microparticles with silicon-vacancy (SiV) centers, offer a robust and unforgeable solution, providing a new frontier in anti-counterfeiting technology that is both durable and secure.

Hybrid Assembly of Polymeric Nanofiber Network for Robust and Electronically Conductive Hydrogels

Hydrogels are promising candidate materials for the construction of soft electronics and biomedical devices due to their mechanical flexibility, structural permeability, and biocompatibility. However, achieving high electrical conductivity and mechanical robustness in hydrogels remains challenging, which limits their practical applications.
Professor Lizhi Xu’s research team has developed a new type of electroconductive hydrogels with outstanding mechanical strength and manufacturability.

A Self-rotating, Single-actuated UAV with Extended Sensor Field of View for Autonomous Navigation

The UAV is named Powered-flying Ultra-underactuated LiDAR-sensing Aerial Robot (PULSAR), whose motion in three-dimensional space is controlled by only a single actuator (i.e., motor). The single actuator design can naturally cause self-rotation motion of the UAV body, obviously extending the field of view (FoV) of the onboard LiDAR sensor. Furthermore, it also effectively reduces the energy loss of the propulsion system, allowing PULSAR to save 26.7% of energy consumption compared to a benchmarked quadrotor UAV. Utilizing the extended FoV and onboard computing resource, PULSAR can perform autonomous navigation in unknown environments and detect both static and dynamic obstacles in panoramic views without using any external instruments. PULSAR has large FoV, high flight efficiency, and autonomous navigation ability, which are all beneficial for the environmental observation and information collection. Therefore, it can be used in various applications, such as environment surveying, search and rescue, terrain mapping, and automatic 3D reconstruction.

Self-powered Multimodal Smart Skin Enabled by Triboelectricity and Hygroelectricity

Tactile e-skins mimicking functions of human skin can sense tactile modalities such as pressure, vibration, temperature, and humidity. They are essential components for smart robotics, health monitoring devices and human–machine interfaces.
However, complicated materials, sophisticated manufacturing, device integration and external power sources are required for most of existing multi-functional e-skins, which severely limit their widespread use.

Ultrastrong and multifunctional aerogels with hyperconnective network of composite polymeric nanofiber

Aerogels are lightweight materials with extensive microscale pores, which could be used in thermal insulation, energy devices, aerospace structures, as well as emerging technologies of flexible electronics. However, traditional aerogels based on ceramics tend to be brittle, which limits their performance in load-bearing structures. Due to restrictions posed by their building blocks, recently developed classes of polymeric aerogels can only achieve high mechanical strength by sacrificing their structural porosity or lightweight characteristics.

On-Demand, Direct Printing of Nanodiamonds at the Quantum Level

Practical realization of quantum devices calls for the placement of individual qubits on complex nanophotonic circuits. However, this prerequisite continues to suffer from coarse positioning accuracy, low throughput, and process complexity. We developed a novel nanoprinting scheme that allows the controllable placement of nitrogen-vacancy (NV) center nanodiamonds at the quantum level. The scheme enables remarkable achievements that are not attainable by other approaches: (1) single-quantum level quantity control, (2) sub-wavelength positional accuracy, and (3) scalable, ‘lithography-free’ patterning capability. We believe this work to be a game-changer, as it directly addresses the key technological challenge associated with the realization of quantum devices. The patent for this invention has been filed (US 63/236,411, PCT Application No. PCT/CN2022/113516).

A Doubling of Annual Tropical Forest Carbon Loss Driven by Agricultural Expansion

Tropical forests are the largest terrestrial component of the global carbon cycle, storing about 250 Giga tons (Gt) biomass carbon in their woody vegetation and absorbing ~70 Gt CO2 per year through photosynthesis. Loss of forests could be devastating because not only the stored carbon stocks in biomass and soil are losing but also the function of sequestering atmospheric carbon.

High-voltage Aqueous Mg-ion Battery Facilitated by Water-in-salt Electrolyte

Although widely used in our daily life, lithium (Li) -ion batteries fall short because the materials used are often scarce, toxic, and expensive. They also have safety issue in operation due to their organic based electrolytes. Beyond lithium-ion batteries, a low-cost magnesium (Mg) metal anode based aqueous Mg-ion battery has been developed first time by Professor Dennis Leung’s research team in the HKU Department of Mechanical Engineering. As Mg is the 5th most abundant metal element in the earth’s crust (three orders of magnitude more than Li), the advantages of low cost and non-toxicity make Mg a desirable alternative to Li as the anode material. The proposed battery shows a high discharge plateau of 2.4-2.0 V and an excellent rechargeability for over 700 stable cycles. This high operation voltage exceeds the counterpart of other multivalent-ion batteries, including zinc (Zn) metal and aluminum (Al) metal batteries. The mechanism behind was also revealed, where a conductive metallic oxide layer was facilitated by the chloride (Cl-) ions inside the water-in-salt electrolyte, providing ionic pathways for rechargeable battery operations. The team hopes that the chemical insights obtained in this work could inspire further optimization and bring attention to the overlooked development of rechargeable aqueous Mg metal batteries. This work uncovers the once dismissed possibility of aqueous Mg metal batteries and opens a new avenue in the field of post-lithium-ion batteries. Other project team members are Dr. Wending Pan (Research Assistant Professor) and Miss Sarah Leong (PhD student).

High-speed Laser-scanning Biological Microscopy using FACED

Laser scanning is used in advanced biological microscopy to deliver superior imaging contrast, resolution and sensitivity. However, it is challenging to scale up the scanning speed required for interrogating a large and heterogeneous population of biological specimens or capturing highly dynamic biological processes at high spatiotemporal resolution. Bypassing the speed limitation of traditional mechanical methods, free-space angular-chirp-enhanced delay (FACED) is an all-optical, passive and reconfigurable laser-scanning approach that has been successfully applied in different microscopy modalities at an ultrafast line-scan rate of 1-80 MHz. Optimal FACED imaging performance requires optimized experimental design and implementation to enable specific high-speed applications. In this protocol, we aim to disseminate information allowing FACED to be applied to a broader range of imaging modalities. We provide (i) a comprehensive guide and design specifications for the FACED hardware; (ii) step-by-step optical implementations of the FACED module including the key custom components; and (iii) the overall image acquisition and reconstruction pipeline. We illustrate two practical imaging configurations: multimodal FACED imaging flow cytometry (bright-field, fluorescence and second-harmonic generation) and kHz 2D two-photon fluorescence microscopy. Users with basic experience in optical microscope operation and software engineering should be able to complete the setup of the FACED imaging hardware and software in ~2-3 months.

Biofilm Inhibition in Oral Pathogens by Nanodiamonds​

Complex microbial communities, e.g., biofilms residing in our oral cavity, have recognized clinical significance, as they are typically the main cause for infections. Diamond nanoparticles, namely, nanodiamonds (NDs) have been demonstrated to work as an effective antibacterial agent against planktonic cells (free-floating state) due to their many promising physico-chemical properties. However, little is known about the behaviors of NDs against biofilms (sessile state).