Poster Z5 - Development of a Wire-Based Electrochemical Glucose Sensor for Integration into Compact Wearable Devices

Friday, October 25, 2024

3:30 PM - 4:30 PM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Hanbyeol Son, Bachelor (he/him/his)

Graduate student
Pukyong National University
Busan, Pusan-jikhalsi, Republic of Korea

Primary Investigator(s)

Hyo-Ryoung Lim, PhD (she/her/hers)

Assistant Professor
Pukyong National University, Pusan-jikhalsi, Republic of Korea

Co-Author(s)

Sueun Choi

Undergraduate student
Pukyong National University, United States

Introduction: The rapid advancement of wearable technology has revolutionized non-invasive, continuous health monitoring through diverse sensors that effectively detect physical and chemical signals from the human body. These sensors, designed for skin or mucous membrane contact, require ultra-miniaturized and unobtrusive designs suitable for integration into compact wearable platforms such as rings, masks, or mouthguards. Although recent studies have achieved minimal form factors using photolithography methods, the high cost of these methods remains a challenge. As a competitive alternative, we propose a small, ultra-thin, and flexible aluminum wire coated with multilayered conductive sensing materials and a thin oxide insulator, achieved solely through cost-efficient wet chemical methods. Our study focuses on the functionality of an Al/Au/CuNi—Al2O3 structure as an electrochemical sensor platform, featuring: (i) an aluminum wire with a diameter under one hundred microns, selected for its ease of coating with a thin oxide passivation layer, (ii) gold coating on a partially exposed aluminum surface achieved through selective oxide etching by immersing the tip in a phosphoric acid solution, and (iii) sensing capabilities after functionalizing the gold surface with a highly porous transition metal complex for non-enzymatic glucose detection. We optimize the deposition quality and sensor efficacy of the porous CuNi deposit by controlling agitation during hydrogen bubble-assisted electrochemical deposition, which also verifies the chemical robustness of the Al—Al2O3 platform. Collectively, our new platform may advance the field of miniaturized, flexible electrochemical sensors for wearable health monitoring applications.

Materials and

Methods: Preparation of Aluminum Wires: We cut aluminum wire (99.999% purity, 0.25 mm diameter) into 10 cm lengths. To anodize the wires, we immersed them in a 0.3 M oxalic acid solution at 15°C and applied 40V for 10 minutes using a DC supply. During this process, we used the aluminum wire as the anode and a Pt plate as the cathode, forming an insulating layer to isolate the sensor area.
Selective Etching: We performed selective etching by immersing the anodized aluminum wires in 85 wt% phosphoric acid at 98°C for 3 minutes. This step exposed part of the aluminum surface to serve as the sensor side.
Electrodeposition of Gold Thin Film: We electrodeposited a gold thin film onto the partially exposed aluminum surface using a commercial potassium gold cyanide-based solution.
Electrodeposition of Glucose Sensing Layer: We prepared a Cu-Ni containing solution for electrodeposition on the gold film. We set the applied voltage to induce hydrogen gas evolution, ensuring the formation of a porous CuNi layer. The deposition quality was optimized by controlling agitation speed.
Sensor Characterization: We characterized the resulting Al/Au/CuNi—Al2O3 wire sensor using cyclic voltammetry (CV) tests at various glucose concentrations to assess its response. We also investigated the effect of agitation during CuNi deposition on the sensor's morphology and performance using scanning electron microscopy (SEM) and CV tests.

Results, Conclusions, and Discussions: Cyclic voltammetry (CV) tests revealed distinct oxidation current increases at 0.5-0.6 V for glucose concentrations ranging from 0.1 mM to 3 mM, demonstrating a clear and consistent response over multiple trials. Increased agitation during CuNi electrodeposition resulted in enhanced glucose sensitivity, as evidenced by the higher oxidation currents recorded during CV tests. Scanning electron microscopy (SEM) confirmed the successful formation of porous CuNi structures, which were induced by hydrogen gas evolution during deposition. Higher agitation rates led to more substantial CuNi deposition, resulting in bulkier structures. This w as evident from the SEM images, which showed a significant increase in the surface area and porosity of the CuNi layer with increased agitation. The sensor exhibited a reliable response to varying glucose concentrations, although we observed peak shifting during multiple CV cycles with a single electrode. This indicates potential challenges with the stability and reproducibility of the sensor over prolonged use. Further analysis showed that the increased agitation during electrodeposition improved the uniformity and distribution of the CuNi deposits, enhancing the sensor's overall performance. However, the bulkier deposition at higher agitation rates requires optimization to prevent excessive material buildup. In conclusion, our wire-based glucose sensor demonstrates a strong potential for miniaturized wearable applications, with distinct and reproducible glucose detection capabilities. Future work will focus on optimizing the deposition parameters to achieve a balance between deposition thickness and sensor performance, ensuring long-term stability and reliability.

Acknowledgements (Optional):