Sehyun Park

(Advisor: Prof. Vladimir Tsukruk)

will defend a doctoral thesis entitled,

Engineered Nanoscale Interfaces for 
Electrophysiological and Electrochemical Sensing

On

Thursday, November 12, 2026 at 9:00 a.m.

Krone Engineered biosystems building (EBB) 3029 Conference Room
and/or virtually via MS Teams

Abstract

The signal quality of a sensing device is largely determined at the interface between the device and its target, a region typically less than a few hundred nm thick. In wearable electrophysiology, this interface must maintain contact with skin that deforms and perspires, whereas in trace-level chemical sensing it must discriminate analytes with few reactive functional groups. In both cases, the thickness and surface chemistry of the interface are usually dictated by the choice of material. This reserach presents two nanoscale interface platforms in which both parameters are defined at the design stage.

The first platform is an ultrathin skin-conformal nano-electrode composed of Ti3C2Tx MXene (50 nm), poly-L-lysine, and parylene (≈300 nm), with the parylene thickness determined from a work-of-adhesion analysis of contact with skin texture. The hydrophilic MXene side and hydrophobic parylene side allow the film to be transferred onto skin by water-assisted capillary flow and to remain attached without gel or adhesive. Compared with commercial gel electrodes, the nano-electrode showed approximately 35% lower skin interfacial impedance and up to threefold higher signal-to-noise ratio in ECG and EMG. ECG was recorded in a sauna and a swimming pool, where gel electrodes detached within minutes, and stable recording was maintained over 30 h of continuous wear.

The second platform is an extended-gate field-effect transistor (EGFET) for tertiary amines of the tryptamine family, with gramine as a structural surrogate for N,N‑dimethyltryptamine (DMT). Since these molecules have no N–H bond and no useful redox activity, selectivity was introduced through chemical activation. Sequential N‑oxidation and Polonovski rearrangement convert the tertiary amine into an amide, which is covalently bound to an amino-terminated self-assembled monolayer on the gold gate by transamidation, and the resulting surface-potential change is read by a commercial MOSFET. The sensor exhibited a limit of detection of 7 nM over four orders of magnitude. In artificial saliva, gramine was still activated in the presence of thiocyanate and urea, and the extraction step of the Polonovski reaction separated the amide from the matrix before surface coupling.

In both platforms, a function normally supplied by an added layer was instead built into the interface itself by controlling its thickness and surface chemistry: water tolerance at the electrode and molecular selectivity at the gate.

Committee

• Prof. Vladimir Tsukruk – School of Materials Science and Engineering (advisor)
• Prof. Eric Vogel – School of Materials Science and Engineering
• Prof. Shucong Li – School of Materials Science and Engineering
• Prof. Peter Hesketh – School of Mechanical Engineering
• Prof. Todd Sulchek – School of Mechanical Engineering