Research at Mei Group

Organic Bio-electronics are a generic platform with unprecedented biological recording and regulation potentials - a technology that bridges biology with electronics. It is based on a unique combination of both electronic and ionic conductivity presented by conducting and semiconducting polymers that enables a means to effectively interface biology with conventional electronics. In our group, we design and synthesize such electronic and ionic polymers, integrate them into organic electrochemical transistors (OECTs), and use these devices to interrogate interesting biological processes such as neural activities, as well as disease diagnosis and monitoring.

Electrochromic polymers are conjugated polymers that reversibly modulate light and heat transmission in response to an applied voltage, and they can be laminated into glass for energy saving and visual comfort. The major obstacles to the market adoption of current electrochromic technologies are (1) premium pricing, (2) the lag in response time between the colored and the bleached states, and (3) the lack of color neutrality (a neutral grey color). In addition, current electrochromic technologies are incapable of turning the millions of existing static windows into dynamic, switchable windows. By applying an adhesive layer to roll-to-roll manufactured thin-film electrochromic foils, which can then be laminated onto flat or curved glass, we investigate an electrochromic technology that is scalable and cost-effective and that fulfills unmet needs in the switchable glass industry. We currently focus on the scale-up synthesis of electrochromic polymers and the roll-to-roll fabrication of electrochromic devices in partnership with industrial experts. To this end, Dr. Mei co-founded Ambilight Inc, a company that brings electrochromic technologies to market.

Machine-learning Assisted High-throughput Automated Synthesis combines machine-learning algorithms with automated chemical synthesis to accelerate the discovery and development of new materials. The approach involves using large-scale, parallel chemical reactors to carry out chemical reactions in a high-throughput manner. Machine learning algorithms are then used to analyze the data generated by the high-throughput synthesis process, including information on reaction yield, purity, and other key metrics, to identify patterns and optimize reaction conditions in real time. By leveraging the power of machine learning, researchers can quickly screen a large number of potential reaction conditions, identify the most promising candidates, and rapidly iterate to optimize the synthesis of target compounds. The use of machine learning in high-throughput automated synthesis is used in the Mei group to accelerate the discovery and optimization of new materials with desired properties. We are increasingly letting large language models and autonomous agents plan, run and analyse experiments, so that the design, synthesis and test loop for new electronic and ionic polymers closes faster than a human can turn it.

Organic Synthesis is a key element in our research. We explore new synthetic approaches to prepare new organic materials including conjugated small molecules and polymers, new polymerisation methods and polymer processing. The performance of n-PBDF, our n-doped transparent organic conductor (n-TOC), rivals indium-tin-oxide (ITO), commonly used in phone screens, displays, and solar cells. In other words, n-PBDF can be inside your phones in the future.

n-PBDF and Polymerisation-Driven Self-Assembly take this further. n-type conducting polymers have long been held back by low conductivity, instability in air and doping that destroys structural order. n-PBDF, discovered independently in our group, is the first to combine metal-level conductivity, air stability, solution processability and visible-light transparency above 80 %. Around it we have built a scalable synthesis, an understanding of its doping mechanism and ways to control its structure, and we discovered polymerisation-driven spontaneous assembly (PSA), in which polymerisation, doping and ordering are coupled in a single step. Doping no longer breaks order; it drives it. The material is a platform for opto-electric (transparent electrodes replacing ITO), electro-chemical (electrochemical transistors, electrochromics), photo-thermal (smart windows, transparent heaters) and thermo-electric (flexible solid-state cooling) devices, and it is the material that living electronics grows in vivo.

Materials Characterization and Processing are also critical components in our research efforts. The essential goal is to establish the relationship among chemical structures-materials processing - thin-film morphologies - functional properties (e.g. mechanical, optical, and electronic properties): our characterisation couples electrical, spectroscopic and morphological measurement to understand how structure sets function.

Device Fabrication and Integration are indispensable when it comes to demonstrating the potential of our materials. There are three primary electronic devices we build in the laboratory, including organic field-effect transistors (OEFTs), organic electrochromic (OECDs), and organic electrochemical transistors (OECTs). One example is our high-temperature electronics. Electronic devices normally lose their function as the temperature rises. We proposed and systematically developed high-temperature organic semiconductors as a research direction, uncovered the mechanisms that govern charge transport and structural stability under heat, and, through polymer blending, realised all-plastic organic transistors that operate stably at 220 °C (Science, 2018, 362, 1131-1134). This takes organic electronics from room-temperature applications into extreme environments such as engines, spacecraft and downhole sensing.