(6ep) Active Soft Materials: Data Driven Study to Understand, Control, and Design Bio-Soft-Materials

Most biological structures are inherently soft and noisy. Soft matter physics holds the key to unlocking several important problems that impact human health, including identification of cancerous cells, and the development of antibiotic-free means to address biofilm infection. Furthermore, studies of such systems inspire engineered advanced materials; these structures pervade personal care, pharmaceuticals, and food products. Soft matter surrounds us in many forms- gels, emulsions, polymers, granular and glassy materials. These systems feature heterogeneous and complex microscopic structures that drive their unique mechanical, rheological, and optical properties. The challenge in identifying, predicting and controlling their properties lies in the weak interactions between their building units and their extreme sensitivity to external stimuli. In this data-driven era, the need for reliable data on complex, highly correlated systems with multiple responsive (living!) structures in paramount. In my research program, I will “study physical aspects of these structures and their complex interactions and dynamics by utilizing state of art experimental tools that provide statistically reliable data”.

My research program will focus on the bio-soft materials particularly cells and cellular communities and their interactions with surroundings. From the perspective of human health, my research will help to find solutions to challenging issues such as high throughput identification of cancer cells and means to mitigate bacterial infection by predicting the response of cells to external stimuli. From the perspective of material science, the outcome of my research will help to design bioinspired materials with particular properties by predicting required microscopic structures.

Background and Future Plans

My background as an experimentalist at the interface of mechanical-chemical engineering and biophysics enables me to approach challenging problems in active soft matter including living cells within a statistical physics framework. I am adept at methods to provide much needed perspective on highly correlated collective dynamics in systems far from equilibrium, including living cells. I specialize in extracting information in highly challenging settings to understand relationships that govern structure formation, dynamics and properties on the micro- and nano-scale and across large domains.

For example, I am currently working to develop high throughput assays to identify cancer cells based on a nano-rheology technique to measure changes in the rheology and stiffness of the cell membrane. This project required that we develop means to follow, in real time, the motion of gold nanorods adhered to different segments of the cells. I have developed a nanoscale rheology technique based on angle resolved dark field microscopy that tracks translation and 3d reorientation of nanoscale probes with high spatial and temporal resolution [1]. This newly developed technique is adaptable to measure mechanical properties of other complex soft materials. We are already applying this method to study the complex rheology of polymer systems, wormlike micelles, and vesicles. This field is wide open for innovation and will form one “basis vector” of my independent program.

I have recently developed a collaboration in Penn Dental Medicine to study biofilm formation in the context of dental caries, a disease that strikes impoverished populations with devastating effects world-wide. To control and remove biofilms we need to better understand their mechanical structure and response to challenges. This project requires that we measure the change in the highly heterogeneous, spatially and temporally complex rheology of biofilms on the microscale when they are exposed to treatment. I approach this challenge by using advanced particle tracking and microrheology to deduce mechanical properties of the biofilm. The method we will develop here are going to applicable to other biofilm related disease including devise related infection such as implants or catheter or non-devise related such as cystic fibrosis.

I am interested as well in the fundamental aspects of active matter- I am working to develop the concepts of active interfaces as a means to remotely enhance transport in microscale and in confined settings. The idea is to arrange and control synthetic and biological self-propelled colloids in a two-dimensional setting to induce enhanced fluctuation and mixing in a three-dimensional fluid. Such active interfaces can potentially introduce a new class of materials such as active Pickering emulsions and revolutionize industrial techniques such as emulsion stabilization and oil recovery. I also study the phase transition, jamming, and glassy dynamics of complex interfaces, such asprotein-, surfactant-, and polymer-laden interfaces. These studies have been performed on a new apparatus that I developed to simultaneously measure surface tension and interfacial rheology.

Active soft materials are often formed by dense populations of active species. To understand the dynamics of individual species and properties of whole systems we need to investigate them in a dense setting but with single unit resolution. For example, in my Ph.D., I extended digital holographic microscopy to track thousands of bacteria in 3D with high spatial (sub-micron) and temporal resolutions [2] to investigate the effect of hydrodynamic interaction on bacterial attachment to solid surfaces [3-4].

In my independent research program, I will integrate my expertise in advanced imaging, microrheology, microfluidics, and microbiology to tackle emergent issues in human health, to design and control novel soft materials, and to improve our fundamental understanding of physics of soft materials.

Teaching Interests:

As an engineering scholar, I am eager to adopt modern teaching methods and hands-on experiences to excite the next generation of STEM leaders. I am especially interested in teaching courses in fluid mechanics, transport phenomena, rheology, and thermodynamics. With a background in chemical engineering, mechanical engineering, and biophysics, I would like to develop interdisciplinary courses such as statistical physics of soft materials and advanced optical techniques in biophysics and soft matter. I would like my teaching to reflect my passion for engineering and biology as well as research-based learning. I am also very interested in mentoring senior design projects that introduce undergraduates to department faculty and their research and to transfer graduate and higher education experiences to undergraduate students. My research program will provide a great platform for training students to integrate multidisciplinary approaches and perspectives to address questions at the interface of biology and engineering.

References:

[1] M. Molaei, E. Atefi, and J. C. Crocker. Nanoscale rheology and anisotropic diffusion using single gold nanorod probes. PRL, 120(11):118002, 2018.

[2] M. Molaei and J. Sheng. Imaging bacterial 3d motion using digital in-line holographic microscopy and correlation based de-noising algorithm. Opt Express , 22(26):32119{32137, 2014.

[3] M. Molaei, M. Barry, R. Stocker, and J. Sheng. Failed escape: Solid surfaces prevent tumbling of Escherichia coli . PRL , 113(6):068103, 2014.

[4] M. Molaei and J. Sheng. Succeed escape: Flow shear promotes tumbling of Escherichia coli near a solid surface. Sci Rep , 6:35290, 2016.