The Need

Modern thermal management demands fast, accurate, and spatially compact heat flux sensing to complement temperature measurements, enable real‑time control, and estimate internal temperatures without waiting for equilibrium. Conventional longitudinal thermopower sensors trade sensitivity for response time due to geometry constraints, while many transverse (Nernst) sensors lack sufficient sensitivity or require external magnetic fields. There is a clear need for a thin, highly sensitive, zero‑field heat‑flux sensor that integrates easily and withstands thermal cycling.

The Technology

OSU engineers have developed a polycrystalline bismuth (Bi) matrix with embedded ferromagnetic MnBi inclusions that transduce heat flux into a transverse anomalous Nernst voltage, orthogonal to the heat flow, without an external magnetic field. Sensitivity is independent of sensor length and scales with width, enabling thin, fast‑response devices and robust contact placement outside the direct heat path. The composite approach enhances the Nernst signal around room temperature while remaining compatible with standard fabrication and packaging. This is similar to Tech ID #T2025-098, except that Bi/MnBi composites are substituted in for Re₄Si₇.

Commercial Applications

• Thermal management and protection for power electronics, EV traction inverters, and battery packs
• Industrial process monitoring (chemical, glass/metal forming) and predictive maintenance
• Aerospace and defense thermal protection systems and avionics cooling
• Smart HVAC and building energy systems for dynamic heat‑flow balancing

Benefits/Advantages

• Zero‑field operation: intrinsic ANE removes magnets and simplifies integration
• High sensitivity with fast response: thin form factor; sensitivity scales with width, not length
• Manufacturable composite: polycrystalline Bi–MnBi avoids costly single‑crystal growth or nanoimprinting used in some alternatives
• Robust contacts and reliability: electrodes can be placed away from intense heat flow to mitigate thermal deterioration