A Tale of Two Motilities
Thursday, October 1, 2026;
10:35am
Capone Learning Auditorium (CBEB 001)
Speaker: Daniel Hammer from University of Pennsylvania
Motility is important for the functioning of the immune system, mostly because immune recognition requires molecular transfer by direct cell to cell contact. We have been studying a fascinating form of cell motility in which T-lymphocytes can migrate against the direction of flow, much like a salmon can swim upstream. Upstream migration is solely due to interactions between a specific lymphocyte receptor, LFA-1, and its natural ligand. Our lab has found that many actively motile cells in the immune system have the ability to migrate upstream. Using CRISPR-Cas9 deletion, we have identified several molecules in cells that are critical for upstream migration; deletion using Cas9 reverses the direction of migration. We have also made the first traction maps of forces exerted by upstream migrating cells. We found that during upstream migration, cells maintain their "architecture," with active forces in the front and rear, but the magnitude of the forces greatly increases, allowing cells to exert sufficient traction to overcome the applied hydrodynamic forces.
Our laboratory is also interested in making synthetic cells, or protocells, that can mimic the behavior of biological cells. In collaboration with Daeyeon Lee at Penn, we have been making inert capsules using microfluidic assembly that can display motility in solution. By attaching urease to the surface of a capsule, we can drive autonomous motion of the capsule in a field of urea. We find that asymmetry of the capsule, in geometry or chemistry, or both, greatly enhances capsule motion. In gradients of urea, our capsules display negative phoresis (move down the gradient). We have preliminary results for the urease-driven motion of Janus capsules, made by microfluidic assembly from mixtures of phase-separating polymers, as a function of the geometry of the capsules.
In the end, we draw analogies between our biological and bio-inspired motile systems, ultimately finding they have little in common.
Daniel A. Hammer is a first-generation college student from New York; he attended Stuyvesant High School, received his B.S.E. from Princeton University in Chemical Engineering in 1982, and received his PhD from University of Pennsylvania in 1987. After spending 8 years on the faculty at Cornell in Chemical Engineering, he moved back to Penn in 1996. Has published > 260 papers, has an h-index of 94, and his papers have over 36,000 citations. He has graduated 65 Ph.D. students. His lab members are on the faculties of U. of Michigan, Northwestern U., Rice U. (2), U.C. Davis, Georgia Tech, Ohio University, Rutgers, U. Massachusetts Amherst, and NJIT (2). He is currently the director of the $100M Center for Precision Engineering for Health (CPE4H) at Penn. He was the BMES Distinguished Lecturer in 2006, and won the Penn Provost Award in 2018 for Ph.D. Mentoring and Advising. He currently serves on the Scientific Advisory Board for the Burroughs Wellcome CASI program, was the Chairman of the Bioinspired Materials GRC in 2022 and was the Robert W. Vaughan lecturer at Caltech in 2003.
Hosted by: Angela Dixon, adc12@psu.edu
Scaling Photonic Computing Across Device, Architecture, and System Levels
Wednesday, September 30, 2026;
3:35-4:25 pm
254 Health and Human Development
Speaker: Nathan Youngblood from
Abstract: Photonics information processing strategies offer the unique ability to perform analog computation with ultra-low latency and high efficiency. However, designing compact and reconfigurable photonic architectures which scale well at the architecture and system level is a challenge. The combination of bistable optical materials (such as phase-change materials like Ge2Sb2Te5 and Sb2Se3) and integrated photonics is a promising approach which enables nonvolatile optical memory on-chip with low drift, compact footprint, and high-speed readout. This talk will first present our work developing robust and scalable photonic memories using phase-change and magneto-optic materials (Ce:YIG) for photonic “in-memory” computing techniques. I will then discuss our recent theoretical and experimental results using coherent photonic crossbar arrays to implement large-scale matrix-matrix multiplication. Finally, I will present a new approach to enable distributed photonic computing over fiber without costly electrical-to-optical or analog-to-digital conversions.
BIO: Dr. Nathan Youngblood, William Kepler Whiteford Faculty Fellow and Associate Professor of Electrical and Computer Engineering, joined the University of Pittsburgh in September 2019. As a postdoctoral researcher at the University of Oxford from 2017 to 2019, he developed phase-change optical systems and photonic architectures for non-von Neumann computing. In 2016, he received a PhD in Electrical Engineering from the University of Minnesota where his research focused on integrating 2D materials with silicon photonics for optoelectronic applications. Nathan is the recipient of the NSF CAREER and AFOSR Young Investigator Awards, as well as the Friedrich Wilhelm Bessel Research Award from the Alexander von Humboldt Foundation for his innovations in optical computing and photonic memory technologies. His work has been published in leading journals such as Nature, Nature Photonics, and Science Advances, and featured in popular news outlets such as The Times, London and the Daily Mail.
Hosted by: Lana Fulton, lub18@psu.edu
