An Lab will build a multidisciplinary research program to establish the scientific base for advanced organic-inorganic composite materials with a deep understanding of the fundamental synthesis-morphology-property relationship. Composite materials couple two or more components (e.g., polymers, ceramics, metals) to obtain functions that exceed the sum of the properties of the components. Rational design of composite materials at the nanoscale has been an emergent direction of efforts where the interaction, morphology, and processing of the components need to be considered synergistically. Such aspects are highly intertwined, whose quantification and visualization at the nanometer level have been met by many challenges, and thus the current efforts are mostly trial-and-error.

In this context, our team bridges the gap in developing tailorable- and predictable-design for advanced composite materials at the nano/micro-scale. We forge a vigorous multidisciplinary program integrating three-dimensional (3D) electron tomography and chemical analysis of composite materials, machine-learning based data-mining, and theoretical modeling to define new opportunities on impactful applications in energy, sensor, and sustainability.

I. Organic-Inorganic Hybrids: Mother Nature's Secrets

Mother Nature has demonstrated amazing hybrid materials, which are strong, light-weight, and multifunctional, constructed from the intimate integration of organic and inorganic components. For example, organic-inorganic hybrid materials such as nacre and bone are well known for their hardness, strength, and resilience. These natural materials consist of brittle minerals connected by small amounts of biopolymer and have highly complex hierarchical structures whose properties far exceed what is obtained from simply mixing these two components together. I have aimed to unravel Mother Nature’s secrets in order to design and tailor-make multifunctional organic-inorganic hybrids. The areas of interest include flexible/structural batteries, surface-agnostic conductive coatings, and sensors.

(1) Polymer/Inorganic Composites for Energy Storage

Flexible batteries are essential for wearable devices and flexible electronics to become more widely available but, most currently available batteries are bulky and rigid and their components are often brittle. We solved that problem by hybridizing vanadium pentoxide (V2O5) with a conductive block copolymer, poly(3-hexylthiophene)-block-poly(ethylene oxide) (P3HT-b-PEO), in order to fabricate a highly flexible battery cathode. The V2O5 layers were arranged in parallel and held together by the block copolymer binder in a brick-and mortar-like fashion resulting in an organic-inorganic hybrid that mimics materials found in nature. This unique structure significantly enhances mechanical flexibility and toughness without sacrificing battery capacity.

Polymers, 11 (4), 589 (2019). [Link]
ACS Appl. Polym. Mater., 1 (5), 1155 (2019). [Link]
ACS Appl. Energy Mater.
, 1 (11), 5919 (2018). [Link]
Langmuir, 33 (24), 5975 (2017). [Link]
ACS Energy Lett., 2 (8), 1919 (2017). [Link]
ACS Appl. Mater. Interfaces, 8 (42), 28585 (2016). [Link]
Sci. Rep., 5, 14166 (2015). [Link] Highlighted in C&EN News.

(2) Conformal Coatings for Sensors

MXenes are a new and exciting class of materials that show great promise for use in the fields of conductive coatings, however, they are lacking in mechanical performance. Using nature as inspiration, I replicated the brick-and-mortar structure of tough and resilient nacre shells using layer-by-layer assembly. This hybridization combined high conductivity, mechanical robustness, and mechanical flexibility. This addresses one of the main obstacles in functional MXene materials and composites: failure and loss of functionality at low strains (4% strain). Furthermore, these MXene multilayer coatings can be deposited on to nearly any surface, regardless of chemistry, topography, or softness. This opens up a range of applications such as human motion sensing, topographic sensors, humidity sensors, and human health monitoring devices.

Langmuir, 37 (38), 11338 (2021). [Link]
Mol. Syst. Des. Eng., 5 (1), 366 (2020). [Link]
ACS Appl. Nano Mater.,
2 (2), 948 (2019). [Link] Selected as Front Cover Art [Link]
NPJ 2D Mater. Appl., 3, 8 (2019). [Link] Highlighted in EurekAlert!, ScienceDaily, Nano Magazine, etc.
Sci. Adv., 4 (3), eaaq0118 (2018). [Link] Highlighted in EurekAlert!, ScienceDaily,, etc.

II. Advanced Soft Materials Characterization

The key challenge in charting the synthesis-morphology-property relationship of composites lies in the long-standing gap of nanoscopic morphology analysis whereas composite synthesis and property aspects each have well-established toolkits. Bulk or advanced statistical methods cannot provide the detailed information on nanoscale morphology. We developed low-dose electron microscope tomography that enables investigations of beam-sensitive soft materials with heterogenous nanoscale morphologies. As a model soft material, We studied polyamide membranes which are used in water desalination, purification of chemicals and pharmaceuticals, and recycling of catalysts. Polyamide membranes have been used in separation industries for over 30 years, however, it is challenging to develop the predictive design of nanometer thin polyamide membranes for two major reasons: it is difficult (i) to investigate the nonperiodic heterogenous nanostructures that emerge from synthesis and (ii) to characterize the 3D soft material structure at the nanoscale. Thus, quantitative understanding of their synthesis–structure–functionality relationship has been limited.

To address these issues, we developed a 3D electron microscopy imaging-quantitative morphometry platform. More specifically, we took over 60 projections at various tilt angles from −60° to +60° and reconstructed a full 3D view with nanometer resolution (i.e., one 3D pixel is 6.8 Å). We quantified various structural parameters governing film transport properties, such as void volume, local curvature, thickness mapping in 3D, and surface-to-volume ratio from the 3D reconstructed image as single data set. We also demonstrated that reaction conditions (i.e., reactant concentrations, reaction time) can serve as a handle on structure parameters like pore structure, local curvature, film thickness, and interconnectivity. 3D imaging and quantitative characterization of soft matter will bridge the structural organization in space and the functionality of materials.

Sci. Adv., 8(8), eabk1888 (2022). [Link]
Nat. Commun., 11 (1), 1 (2020). [Link]
Mol. Syst. Des. Eng., 5 (1), 102 (2020). [Link] Featured as Front Cover. Selected as a HOT article.
ACS Appl. Nano Mater., 3 (2), 937 (2019). [Link] Featured as Front Cover.
ACS Appl. Mater. Interfaces, 11 (8), 8517 (2019). [Link]