The human body, such as the brain, produces a wide range of biophysical and biochemical signals that contain important information about the health condition and the progression of various diseases. There are critical challenges, however, to efficiently capture the signals due to the rigid characteristics of conventional medical systems. To address this issue, the design of thin, soft and flexible electronics forms the basis of novel wearable and implantable biomedical devices for the diagnostics and treatment of brain injuries and other chronic neurodegenerative diseases with improved outcomes and reduced costs. Our research focuses on advanced thin-film materials and electronic tools to bring solutions to grand challenges in human health.

Overall, we have two main thrust areas:

1) fundamental understandings on synthesis chemistry and interfacial properties of thin-film materials as bio-interface by combined experimental and theoretical methods, and innovative approaches to assemble materials with tunable structures and properties across multiple scales;

2) engineering efforts on application of these materials for the next generation wearable biomedical devices to bridge the gap between rigid machine and soft biology.

Together, these materials and electronics provide a realistic pathway to biomedical devices with biocompatibility, bioconformality and biostability for the applications in closed-loop neuromodulation and neuroscience research.

Chemical synthesis of low-dimensional electronic materials with structure control at the molecular level

Materials at nanometer scale can demonstrate unique and outstanding electrical/mechanical properties different from those in bulk forms. Therefore, the controlled synthesis of nanomaterials is of interests for the development of advanced nanoelectronics and bioelectronics. We aim to understand the chemical equilibrium of pyrolysis and nucleation of carbon-containing molecules at metal/carbon interfaces for the controlled synthesis of graphitic carbon nanostructures (e.g. carbon nanotubes) using chemical vapor deposition method. We are interested in how electronic structures and bandgaps of nanocarbons can affect their reactivity with oxygen-containing molecules to achieve selective synthesis and purification. Based on these understandings, We develop synthetic strategies to design sp2 C-C formation reactions to form carbon nanotubes with tailored alignment, chirality, and electrical properties. These studies provide important insights into the control of the electronic structures of graphitic carbon-based materials and the development of biochemical interfaces for the detection of biomarkers with high sensitivity and selectivity.

Kinetics and chemistry of hydrolysis of electronic materials in biofluids

Thin-film materials as the biointerfaces that enable long-term, intimate coupling of flexible electronic devices to biological systems are critically important to the development of advanced biomedical implants for biomedical research and clinical practices. Our research aims to explore the behavior of thin-film materials (e.g. ceramics, polymers) in aqueous solutions with chemical compositions relevant to biofluids. Specially, we investigate the physical and chemical interactions at biotic/abiotic interfaces, including hydrolysis reactions, corrosion chemistry, ion diffusion and adsorptions of biomolecules. The research establishes foundational data of relevance to predicting degradation behavior and lifetimes of materials in biofluids. These understandings can enable the development of chronically stable bioimplants that can survive in animal models/human body for decades of years, and they have broad applications for safe and reliable diagnostics and therapeutics in biomedical research and clinical practices.

Soft, wearable/implantable electronics for biophysical/biochemical information

We are also focusing on the implementation of thin-film materials for recording and stimulation in the nervous system to extend the frontier of human healthcare. We work on the design and innovation of Si nanomembrane as interface to the brain for flexible micro-electrocorticographic (╬╝ECoG) arrays with multidecade lifetimes under physiological conditions. The technology enables flexible, actively multiplexed ╬╝ECoG electrodes for recording and stimulation in nervous systems with chronic stability, high sensitivity, and unprecedented level of spatiotemporal resolution. In parallel, our research also focuses on the design and manufacturing of stretchable epidermal electronics (also known as “electronic tattoos”) capable of continuously measuring high-quality electrophysiological information on skin surfaces, including electromyography (EMG) and electroencephalography (EEG) signals.