Minhee Yun, PhD

Associate Professor

Department of Bioengineering (secondary)

218 E Benedum Hall | 3700 O’Hara Street | Pittsburgh, PA 15261 P: 412-648-8989

miy16@pitt.edu

Highly Sensitive and Selective Biosensor Development

In this research, we have developed polyaniline (PANI)-based biosensors (top figures) for detecting four cardiac biomarkers in serum and human bloods, including Myo, cTnI, CK-MB, or BNP. The PANI was directly fabricated via both electrochemical deposition and chemical synthesis methods between pre-patterned Au electrodes. Hence our polymer growth is a mass producible and reproducible method. For the functionalization of the fabricated PANI (1-D and 2-D structures), the mAbs of cardiac markers were covalently attached to PANI by a surface immobilization method. After the PANI functionalization, the biosensing of cardiac biomarkers was carried out by measuring the conductance change of the biosensor. The conductance of PANI was monitored in the various conditions of the functionalized PANI, injecting phosphate buffer saline (PBS), bovine serum albumin (BSA), and target biomarkers. The conductance of nanowire can be modulated by the major carrier accumulation or depletion. The binding between immobilized mAbs and target biomarkers changes the net surface charge of the PANI and induces the carrier accumulation or depletion depending on the values of net surface charge and types of PANI. In addition, the developed biosensor shows non-response of conductance change to BSA or non-target proteins due to the mAbs specificity.

Graphene-Engineered Devices

We are investigating graphene-based materials for various device applications. In particular, our current focus is infrared sensor development based on graphene and graphene-oxide materials. The goal of this research is to investigate thermoelectric graphene and thermal graphene oxide (GOx) infrared radiation (IR) sensors that will operate at uncooled temperatures. The specific aims of this research are; (1) understanding of critical parameters for IR detectors, (2) development of thermoelectric IR sensor based on graphene, and (3) development of thermal IR sensor (bolometer) based on GOx. The primary scientific focuses of this research are (i) to identify responsible parameter for producing the wideband IR and backgrounds so that the proposed work will improve the understanding of graphene and GOx properties for IR sensor applications, (ii) to determine the key advantages of the graphene/GOx based IR detector approach that offers inherent broad frequencies and enhanced sensitivities without the need for bulky filters, and (iii) to conduct wide range IR surveys of the thermal emissions from hot objects at room temperature.

Current Results:

To realize a proof of concept graphene-based IR sensor, we have fabricated thermopile devices using multilayer graphene (MLG) on the top of a freestanding SiNx membrane and established a substantial temperature gradient on the device as shown in the figure (bottom). To demonstrate the IR sensor operation, graphene channels were placed such that long and narrow MLG channels are positioned on free-standing SiNx membrane (hot zone), whereas a wide graphene heat sink is located on the top of Si substrate (cold zone).