One research focus in the Liu group is the investigation and design of microenvironments, through electrochemistry and materials, to mimic natural microbial habitats, enable new studies in microbiology, and facilitate efficient biocatalysis powered by renewable energy. The microbial exchange of energy and matter with their immediate surroundings, the microenvironments, is critical to microbial metabolisms and regulations in environment, energy, and biomedical applications. At UCLA, the Liu group designs advanced bio-abiotic interface in order to facilitate the reaction of electricity-driven microbial fixation of CO₂ and N₂, and provide a comprehensive picture about the interplay between materials and microbiology, with characterizations of materials science and microbiology, in different scenarios of bio-based chemical transformations. Moreover, the Liu group employs nanomaterials and electrochemistry to spatiotemporally control the extracellular space in microbiology. We developed biocompatible electrochemical platforms that spatially and temporally modulate the concentration profiles of biologically important  small molecules such as O₂ and reactive oxygen species (ROS). We envision that our electrochemistry-enabled spatiotemporal control of extracellular space not only mimics the natural microbial habitats but also serves as a quantifiable perturbation towards the microbial ensemble. Such platforms will offer valuable information about the dynamic response and spatial propagation of collective behaviors in diverse microbial communities.

In line with the concept of controlling microenvironments for microbiology in Thrust 1, the Liu group also envisions to electrochemically create microenvironments and establish new catalytic cycles seemingly impossible in solution. We hypothesize that we can expand the design space of catalysis by utilizing microscopic concentration gradients, for example microenvironments generated by electrochemistry and nanomaterials, to establish solution catalysis impossible in homogeneous solution. For example, we demonstrated a new solution catalytic cycle of ambient CH₄-to-CH₃OH conversion with O₂ as oxidant, which utilizes O₂-deactivating, CH₄-activating Rh(II) metalloradiacls for O₂-based CH₄ oxidation into CH₃OH. The nanowire array of electrochemical O₂ reduction creates a microscopic O₂-free domain within the wire array, and effectively establishes a compartmentalized “mini-glovebox” in air that allows diffusion and the synchronization of aerobic and anaerobic steps into a complete catalytic cycle. Furthermore, we generalized this concept and established a design principle based on a general kinetic model of organometallic catalysis. We reported a set of conditions under which spatially controlled organometallic catalysis or compartmentalized ones will be advantageous. Our work reminds the community that compartmentalization or spatial control of catalysis is not necessarily a panacea for all applications in organometallics, hence paving the road towards a rational design of spatially controlled organometallic reactions.

A fledging research thrust in the Liu group is the use of ML and AI to address the challenges not only synergistically in our aforementioned research areas but also in the general field of electrochemistry and nanomaterials. We envision that a wider application of our electrochemically generated microenvironments (Thrust 1 and 2) requires a fast ML-based inverse design towards the physical and chemical properties of electrochemical nanomaterials, in order to satisfy the diverse and varying scenarios of microenvironments in microbiology and catalysis. We are also actively developing is the use of AI to automatically analyze electrochemical data such as cyclic voltammograms in the context of fully automated electrochemical research. We believe ML and AI will transform how we conduct research in the field of electrochemistry and nanomaterials, for a myriad of applications in energy, environment, and biology.