Physics & Engineering Physics Colloquia

Ernesto (Trey) Feliciano, Physics Major, FCRH 2026 will present: “Mucin and Polyvinylpyrrolidone Solutions Affect E. coli Motility”

Abstract: Knowledge about how bacteria move through viscoelastic media can be helpful in
understanding how they move through medical solutions using such media or move
through mucus to infect humans.

Previous research has been conducted on how they collectively move through synthetic
mucus, polyvinylpyrrolidone (PVP) solutions, and media mimicked by carboxylate
microspheres. Research about the individual cell movements in synthetic mucous has
not yet been intensively observed. The kinematics of the individual cells of a certain
motile strain of E. coli through various concentrations of viscoelastic media, including
artificial mucus and PVP solutions, were observed in this project.
Results showed that certain concentrations of mucin in mucus aid bacterial motility,
whereas high concentrations of mucin inhibit it. For PVP, velocity remains relatively
constant until it decreases at higher concentrations. By understanding how
concentrations of viscoelastic fluids affect bacterial motion, knowledge about why the
human body secretes more mucous along the respiratory tract during infections or
about what qualities of viscoelastic medical solutions are ideal for usage can be
enhanced.

Jenna Cain, Engineering Physics Major, FCRH 2026 will present: “Optimizing Geometric Fill Factor and Interconnection Between Thermophotovoltaic(TPV) Cells on a Tile”.

Abstract: Thermophotovoltaic (TPV) cells convert high-temperature thermal radiation (1,000–
2,000 °C) from an emitter directly into electricity, resulting in power densities up to 500 times
greater than a conventional solar cell. Advancements in TPVs at the University of Michigan over
the past decade have led to the development of the Air-Bridge TPV, which has a world-record
efficiency of 44%, and is being scaled up for implementation in thermal batteries. To scale up
single cells into functional panels, many cells must be interconnected into one electrical system
on a tile (4″ growth substrate). Here, I developed an interconnection process for TPV cells that
minimizes the spacing between cells to maximize the amount of active area, or the geometric fill
factor, for a tile. In our approach, we use simple resistor-mesas to replicate the width and height
of the target TPV cells and aim to interconnect the top contact and bottom contact on adjacent
mesas (3 μm step height). We use a polyimide passivation film that serves as an insulating barrier
between the active regions of the devices and the conductive interconnects. In this work, I
demonstrate that a 1 μm polyimide film provides sufficient sidewall coverage to enable
interconnections between mesas separated by as little as 45 μm. Optimal curing temperature of
350°C and time of 1 hour was determined by monitoring the diminishing anhydride group of
polyimide precursor via Fourier Transform Infrared Spectroscopy. Successful interconnection was
demonstrated by patterning 1 μm silver interconnections between resistors and measuring the
cumulative resistance for each string of interconnected resistors. For all mesa spacings – 45 μm
to 500 μm – successful interconnection was demonstrated. Future work will explore
interconnection across shorter distances to continue optimizing geometric fill factor.