The term bioelectricity might conjure up images of Victor Frankenstein, or perhaps unscrupulous quack doctors in traveling medicine shows. Despite the warped public perception, electrochemical potentials are indeed a fact of life, influencing processes in transport, metabolism, computation, and development across all the biological kingdoms. By developing devices that interface with these bioelectric systems, engineers may be able to observe or even control these processes for sensing, manufacturing, or medical applications that were not possible before.
There’s a complication: the wet, salty electrochemistry that comprises most bioelectric systems is not immediately compatible with the integrated circuits that drive our digital world. Care must be taken at the interface between electronics and living organisms to keep both the electronics and organisms happy. This interface has been at the core of my research work, whether it involves the electroactive bacterium Shewanella oneidensis or skin cells sheepherded in a petri dish. I am engineering devices that use this bioelectrical connection to augment these biological systems for biosensing and medical applications.
SCHEEPDOG: Steering cell motion with electrical stimulation
I developed SCHEEPDOG, a device that exploits electrotaxis, the ability of cells to sense electric fields and follow them, to shepherd cell migration. SCHEEPDOG uses two orthogonal electrode pairs, one vertical and one horizontal, to create a composite field direction. By adjusting field directions over time, cells can be herded along arbitrary trajectories, akin to how an ‘Etch A Sketch’ traces out a picture via two control knobs. With SCHEEPDOG, we have induced a potpourri of novel dynamic maneuvers in skin and kidney cells: 90-degree turns, diagonals, sinusoids, and circles (pictured above). The level of control demonstrated suggests that cells effectively time-average electric field cues on the order of ~5 minutes, which helps to clarify the time scales involved in the biological response. Because electrotaxis has been documented across diverse systems including at least 20 mammalian cell types, slime molds, fish, and frogs, our platform represents a control approach with potentially broad utility in many arenas.
- T.J. Zajdel*, G. Shim*, L. Wang, A. Rossello-Martinez, D.J. Cohen, SCHEEPDOG: programming electric cues to dynamically herd large-scale cell migration, Cell Systems, vol. 10, no. 6, pp. 506-514, 2020.
- M. Sharlach, Researchers use electric fields to herd cells like flocks of sheep, Princeton Engineering, June 2020.
People’s Ventilator Project
During the worst stages of the COVID-19 pandemic, there was an unmet global need for easily manufactured, rapidly deployable mechanical ventilators. The People’s Ventilator Project was started to meet this need, bringing researchers together across Princeton University and beyond to design an open-source, replicable ventilator that could adapt to shifting global supply chains. I developed printed circuit boards to interface pressure and flow sensors and valves with a Raspberry Pi to control the system. I am also carrying out standard testing to certify the ventilator for emergency use. Contributing to this project has been a great honor, and I would like to acknowledge the fantastic team: Julienne LaChance, Daniel Cohen, Daniel Notterman, Lorenzo Seirup, Chase Marshall, Grant Wallace, Jonny Saunders, Manuel Schottdorf, Zhenyu Song, Al Gaillard, Sophie Dvali, and Moritz Kuett.
- D. Krakow, Tom Zajdel: From Skin Wounds to Ventilators, Princeton MAE Spotlight, June 2020.
- C. Sayre, Julienne LaChance: Sharing Accessible Ventilator Plans with the World, Princeton MAE Spotlight, June 2020.