PolyU’s Programmable Liquid Processing Innovation

Fluidic technologies are crucial in fields requiring precise control over the capture and release of chemical and biological fluids, but achieving accurate spatial and temporal control has been challenging.  Researchers at The Polytechnic University of Hong Kong (PolyU), led by Prof. WANG Liqiu, have developed a novel fluidic processor called “Connected Polyhedral Frames” (CPFs). This innovation provides precise, switchable control over liquid capture and release, offering a new solution for applications needing accurate volumetric control.

This innovation represents a significant advancement in fluid handling, offering reversible, programmable, and independent switching between liquid capture and release. The CPFs are characterised as a meta-metamaterial because they transcend traditional material and design limitations, functioning effectively regardless of the type of polyhedral frames or the specific liquids being processed. The research, detailing the development and potential applications of CPFs, has been published in a prominent journal in the field.

In contrast to the well-established techniques for manipulating solids, fluid handling remains a challenging and often cumbersome task. Fluids are ubiquitous in industries such as healthcare, pharmaceuticals, and chemical processing, yet their interaction with tools often leads to issues like wetting and spreading on solid surfaces. These interactions can result in incomplete liquid transfer, compromised volumetric accuracy, and cross-contamination between samples. To mitigate these issues, disposable plastics like pipettes and microtubes are commonly used, contributing to the growing problem of plastic waste.

The reversible switching capability of CPFs is key to their ability to process liquids with high precision. Within the CPF structure, specific frames capture and retain liquids, while others are designed to release them. This functionality is achieved through the strategic arrangement of single-rod and double-rod connections within the frames. When the CPFs are lifted from a liquid, a film forms between the double-rod connections, creating channels that facilitate the release of the liquid. This mechanism allows for the dynamic, localised, and reversible control of fluid retention and drainage within the network.

The CPFs offer a versatile platform that supports a range of unique functions, including 3D programmable patterning of liquids, spatiotemporal control of material concentrations, packaging of liquid arrays, and large-scale manipulation of multiple fluids. The technology is compatible with a wide variety of liquids, including aqueous solutions, biofluids, hydrogels, organic solvents, polymer solutions, and oils. This broad compatibility allows for the incorporation of various biomaterials and chemicals, making CPFs applicable in a wide range of industries.

One practical application of CPFs demonstrated by the research team is in a controlled multidrug release. The team designed a CPF network for 3D binary liquid patterning using vitamins B2 and B12, encapsulated in different hydrogel matrices. By adjusting the thickness of the gel membranes, the release rates of these drug analogues could be precisely controlled, showcasing the potential of CPFs in pharmaceutical applications.

Traditional methods of fluid sampling, such as cotton and flocking swabs, often suffer from sample residue issues. CPFs, with their unique frame structure, offer a solution to this problem by providing free liquid-liquid interfaces that enable more efficient release of samples. The research team demonstrated this advantage using the influenza virus as a test case, where CPFs outperformed traditional swabs, particularly at low virus concentrations.

Beyond medical applications, CPFs have shown promise in biomaterial encapsulation and air conditioning. For instance, when applied to the encapsulation of Acetobacterium, CPFs facilitated the separation of bacteria from reaction products, simplified the microbial reaction process, and enhanced bacterial utilisation rates. In air conditioning, CPFs were used to develop a commercial-scale humidifier prototype with higher water storage capacity and lower water flow requirements, making it more energy-efficient. Additionally, CPFs enabled large-scale 3D liquid dispersion, creating a larger surface area for gas absorption, which is beneficial for processes like CO2 capture and re-utilisation.

The development of CPFs represents a significant advancement in fluidic technology, offering a new standard for liquid handling with enhanced controllability, versatility, and performance. The innovation not only sets the stage for new scientific and technological breakthroughs but also inspires the emergence of a new field of meta-metamaterials, with wide-ranging implications across various industries.