(2l) Engineering and Applications of Molecularly Assembled Architected Soft Materials

A grand challenge in soft matter engineering lies in integrating characterization, prediction and design of molecular structure and dynamics across length-scales. My work integrates field-guided molecular assembly with single-digit-micron resolution additive manufacturing (AM) technology to pattern freeform, mechanically robust, and functional architected materials. Soft matter exhibits disparate behaviors across length and time scales, such that microstructure, non-equilibrium dynamics dictate a material’s macroscopic response and applicability. To elucidate and utilize underlying heterogeneity of material structural and transport properties, my research investigates field-guided interactions using multiscale experimental characterizations, including single molecule fluorescence microscopy, opto-mechanical testing, and light and neutron scattering. This approach enables strategic design of materials to accelerate the current material engineering pathways to design architecturally customized, functionally graded soft materials. Initial research areas in my proposed research program include flow-assembly of stretchable conjugated polymers bioelectronics, bio-printing of nanocomposites for bone-mimetic 3D vasculatures, and functionally-graded nanocellulose membranes for water purification.

Research Experience:

Development of Single-Digit Micron CLIP 3D Printing, Department of Chemical Engineering, Stanford University (advised by Joseph M. DeSimone)

My postdoctoral research has focused on developing a novel 3D printing technology that combines micro-DLP with Continuous Liquid Interface Production (CLIP) technology to deliver single-digit micron scale print resolution with a printing speed up to 10⁵ greater conventional high-resolution printing technologies. To this end, I have developed a customized projection optics, an in-line camera system to monitor the projection pattern and a stand-alone contrast-based focusing algorithm to achieve an optimal projection plane. To optimize and provide a full understanding of the high-resolution CLIP 3D printing process, I have developed a physical model that involves Zemax based optics point spread function prediction, first principle’s reaction kinetics modeling and lubrication theory-based momentum transport theory that provides insights into the photopolymerization gradient, flow velocity profile and mass transport in the CLIP system. It was observed both experimentally and from modeling that a delicate control of UV projection intensity, printing step size, and waiting time between exposures are critical to achieving the desired resolution. A physical model informed software-controlled printing strategy was adopted, and the step-and-expose printing process allowed us to resolve single-digit micron prints with high-precision. The high-resolution 3D CLIP printer has overcome the major technological challenge of scalability and print resolution platform. This work presents a new paradigm for fabrication of various soft materials (including hydrogels and elastomeric materials), with many applications ranging from drug delivery and continuous health monitoring platforms to microfluidic and force sensors.

Single Polymer Dynamics of Linear and Architecturally Complex Chains in Semi-Dilute Solutions, Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign (advised by Charles M. Schroeder)

My dissertation research extended the field of single polymer dynamics and micro-rheology to concentrated polymer solutions and ring polymers, to elucidate the molecular level origin of non-Newtonian polymeric material properties. The majority of single polymer studies has focused on linear and dilute DNA solutions, but concentrated polymer solutions and ring polymers exhibit drastically different flow behaviors in comparison to their linear counterparts, including lack of entanglement observed in ring polymers and complex flow properties observed in concentrated polymer solutions. My Ph.D. work combined single molecule visualization, micro-rheology, Brownian dynamics simulations and constitutive fluid mechanics modeling, to understand the flow properties of semi-dilute and concentrated linear and architecturally complex ring-shaped DNA molecules. Microfluidic devices were used to control the extensional flow fields for manipulating single DNA molecule, while directly visualizing the conformational dynamics of single polymer during flow-induced stretching and relaxation. Single molecule experiments revealed the molecular individualism and unexpected stretching pathways of linear and circular DNA in concentrated solutions, in agreement with Brownian dynamics simulations. The micro-rheology experiments of flow induced particle migration in concentrated DNA solutions further relates the molecular scale interactions to solution extensional viscosity. This research provided fundamental understanding of ring polymers, concentrated polymers in flow, and bridge the knowledge gap between molecular-scale structure and response of non-Newtonian fluid dynamics.

Successful Proposals: Stanford Wu-Tsai Seed Grant (May, 2022), Stanford PHIND seed grant (April, 2022), Stanford Precourt for Energy Efficient Computing (Aug 2021), Wellcome Leap (Aug 2021)

Selected Publications:

• K. Hsiao*, B. J. Lee*, T. Samuelsen, A. Shih, G. Lipkowitz, J. M. DeSimone “Single Digit micron high-resolution CLIP”, in prep. * Equal contributions (under revision at Science Advanced)
• G. Lipkowitz, T. Samuelsen, K. Hsiao, B. Lee, M. Dulay, I. Coats, H. Lin, G. Toth, L. Tate, E. Shaqfeh, J. M. DeSimone “Vat injection additive manufacturing through spatioselectively-programmable microfluidic ducts” (under revision at Science Advanced)
• B. J. Lee*, K. Hsiao*, G. Lipkowitz, T. Samuelsen, J. M. DeSimone “Characterization of a 30-micron pixel size CLIP-based 3D printer and its enhancement through dynamic printing optimization”, under review in Additive Manufacturing. Additive Manufacturing, 55, pp 102800 (2022)
• Y. Zhou, K. Hsiao, K. E. Regan, D. Kong, G. B. Mckenna, R. M. Robertson-Anderson, C. M. Schroeder “Effect of molecular architecture on ring polymer dynamics in semidilute linear polymer solutions”, Nature Communications, 10(1), pp 1753, (2019).
• K. Hsiao, C. Sasmal, R. Prakash, C. M. Schroeder. “Direct observation of DNA dynamics in semidilute solutions in extensional flow", Journal of Rheology, 61, pp 151-167 (2017). Chosen to be Cover Art.
• K. Hsiao, J. Dinic, Y. Ren, V. Sharma, C. M Schroeder. “Passive non-linear microrheology for determining extensional viscosity" Physics of Fluids, 29(12), pp 121603 (2017)
• C. Sasmal, K. Hsiao, C. M. Schroeder, R. Prakash. “Parameter-free prediction of DNA dynamics in planar extensional ow of semidilute solutions", Journal of Rheology, 61, pp 169-186 (2017)
• K. Hsiao, C. M. Schroeder, C. E. Sing "Ring polymer dynamics are governed by a coupling between architecture and hydrodynamic interactions" Macromolecules, 49(5), pp1961-1971 (2016)
• Y. Li, K. Hsiao, C. A. Brockman, D. Y. Yates, G. B. McKenna, C. M. Schroeder, M. J. San Francisco, J. A. Kornfeld, R. M. Anderson. “When Ends Meet: Circular DNA Stretches Differently in Elongational Flows" Macromolecules, 48(16), pp 5997-6001, (2015)
• F. Latinwo, K. Hsiao, C. M Schroeder "Nonequilibrium thermodynamics of dilute polymer solutions in ow" The Journal of chemical physics, 141(17), pp 174903 (2014)
• M. Wu, H. Hsu, K. Hsiao, C. Hsieh, H. Chen, “Vapor-Deposited Parylene Photoresist: A Multipotent Approach toward Chemically and Topographically Designed Biointerfaces". Langmuir, 28, 14313-14322, (2012).

Patents:

[2] “Dynamic, 3D-printed microarray patches and related structures with compliant mechanisms.” Ref: 63/333655

[1] “3D printed lattice microneedle for therapeutic, drug and vaccine delivery and liquid sampling, including interstitial fluids”, Ref: 63/248280

Selected Awards:

• Stanford Wu-Tsai Human Performance Fellow (2022)
• Stanford Bio-X Travel Award (2022)
• ACS Polymeric Materials Science and Engineering Future Faculty Award (2022)
• Stanford Molecular Imaging Program (MIPS) retreat poster presentation First Prize (2021)
• ChBE Graduate Symposium Presentation Second Prize (2017)
• GLCACS Outstanding Student Research Award (2016)
• AIChE Selected presentation: Excellence in Graduate Polymer Research (finalist) (2016)
• UIUC ChBE Spring Hanratty Travel Award (2016)
• Mavis Future Faculty Award (2014)

Teaching Interests:

As a chemical engineer by training, I am excited and qualified to teach core coursework in transport phenomena, thermodynamics, fluid mechanics, chemical kinetics and process dynamics and control courses at all levels. I also look forward leveraging my research experience and interests to develop and teach electives in soft matter physics, polymer science and engineering, non-Newtonian fluid dynamics, additive manufacturing, and nonequilibrium statistical mechanics. My teaching extends beyond the classroom into the laboratory, and I aim to engage students and postdoctoral researchers in my group to participate in interdisciplinary research approach toward soft-matter materials engineering, by drawing expertise in chemical engineering, physics, materials science, and bioengineering.

Teaching Experience:

• Advanced Heat and Mass Transfer (Illinois ChBE), Teaching Assistant (2016)
• Advanced Fluid Dynamics (Illinois ChBE), Teaching Assistant (2015)
• Momentum and Heat Transfer (Illinois ChBE), Teaching Assistant

Service:

I am committed to make contributions towards promoting a diverse, equitable, and inclusive learning environment. At the University of Illinois, I organized ChBE graduate research symposium and invited departmental alumni from both academia and industrial background as guest judges to engage students with researchers from diverse scientific fields. To provide a welcoming campus community for all students, I volunteered at University of Illinois global leader (GLOBE) where I led weekly gatherings for newly arrived international students. At Stanford University, I volunteered as mentor at Stanford Micro-Internship (SLI) mentoring program, where I mentored an under-represented, financially challenged college student to advance his skills in future career. I also participated in Stanford research for undergraduate (REU) program, where I mentored Stanford undergraduate students who have no prior research experiences with an aim to inspire them to pursue education and research in STEM. As a postdoc in DeSimone Lab at Stanford University, I have mentored 7 graduate students and undergraduate students in total and am continuously developing my mentoring skills. In 2022, in pursuit to recognize the contributions of diverse researcher in polymer science and engineering, I accepted a role as a co-chair at 2022 ACS PMSE seminar. I deeply value the richness of scientific communities and I hope to contribute to their sustained growth.