Lab-on-a-chip transforms blood conductivity testing

This millifluidic nanogenerator lab-on-a-chip device, as detailed in the recent study by researchers at the University of Pittsburgh and University of Pittsburgh Medical Centre, employs a method that uses blood itself as a conductive medium. The research, published in Advanced Materials, highlights the device's potential to simplify and enhance blood analysis processes significantly.

Metabolic disorders like diabetes and osteoporosis are becoming increasingly prevalent worldwide, especially in developing countries. Diagnosis for these disorders typically involves a blood test, but existing healthcare systems in remote areas are often unable to support such tests, leaving many individuals undiagnosed and untreated. Conventional methods also involve labour-intensive and invasive processes, making real-time monitoring unfeasible, particularly in rural settings.

Traditional comparison

Blood tests provide critical information about a person's health and blood conductivity is predominantly governed by the concentration of essential electrolytes, notably sodium and chloride ions, which are integral to a multitude of physiological processes. This device was compared with traditional blood conductivity measurement methods such as impedance plethysmography, bioimpedance analysis, and four-electrode conductivity measurement. These conventional methods often require bulky, power-dependent equipment and complex calibration procedures, making them unsuitable for point-of-care and remote monitoring applications.

The proposed lab-on-a-chip device, however, offers simplicity and portability by eliminating the need for external electrodes and power sources. This innovation addresses the limitations of traditional techniques, enhancing its potential for use in various medical diagnostics and research applications.

Despite its importance, the knowledge of human blood conductivity remains limited due to measurement challenges, such as electrode polarization, limited access to blood samples, and the complexities associated with blood temperature maintenance. Measuring conductivity at frequencies below 100Hz is particularly important for gaining a deeper understanding of blood's electrical properties and fundamental biological processes, yet this is even more challenging.

Portable lab-on-a-chip

The research team has proposed an innovative portable millifluidic nanogenerator lab-on-a-chip device capable of measuring blood at low frequencies. The lab-on-a-chip device integrates a triboelectric nanogenerator (TENG) system, where the blood serves as a conductive layer within a sealed chamber. This portable device converts mechanical energy into electrical energy through triboelectrification, generating a voltage signal that directly correlates with the blood's electrical conductivity.

In a TENG system, this electron transfer and charge separation generate a voltage difference that drives electric current when the materials experience relative motion, such as compression or sliding. The team analyses the voltage generated by the device under predefined loading conditions to determine the blood's electrical conductivity. The self-powering mechanism enables the miniaturisation of the blood-based nanogenerator.

The device's design allows it to function without complex electronics or external electrodes, making it particularly suitable for point-of-care (POC) applications.

Key features and benefits

• Portable and disposable: The 3D-printed device is designed for single-use, ensuring hygiene and ease of use in various settings, including remote areas.
• Self-powering: The TENG system within the device eliminates the need for external power sources, enhancing its portability and usability in resource-limited environments.
• Accurate and rapid measurement: By analysing the voltage generated by the blood-based TENG, the device can accurately determine blood conductivity, offering quick assessments without the need for extensive laboratory equipment.

Addressing the challenges of blood conductivity measurement

The device's performance was also evaluated under varying temperature conditions, ranging from 10°C to 40°C. The results indicated that both the voltage generated by the device and the electrical conductivity of the blood increased nearly linearly with rising temperatures. This correlation underscores the importance of considering temperature variations when deploying the device in practical field applications. By understanding and calibrating for these temperature effects, the device can provide more accurate and reliable measurements across diverse environmental conditions.

To test its accuracy, the team compared their results with traditional tests, which proved successful. This opens the door to conducting tests where people live. In addition, blood-powered nanogenerators can function in the body wherever blood is present, enabling self-powered diagnostics using local blood chemistry.

The device addresses several challenges associated with traditional blood conductivity measurement methods:

• Remote healthcare: The portability and simplicity of the device make it ideal for use in remote areas, where access to advanced medical facilities and equipment is limited.
• Point-of-care diagnostics: Its quick and accurate measurement capabilities facilitate immediate decision-making in clinical settings, improving patient outcomes.
• Research and development: The device's ability to measure blood conductivity at low frequencies opens new avenues for research into the electrical properties of blood and its relation to various physiological processes.

The millifluidic nanogenerator lab-on-a-chip device represents a significant advancement in the field of medical diagnostics. By offering a portable, self-powered, and accurate method for measuring blood electrical conductivity, this device has the potential to bring up to date how blood tests are conducted, particularly in remote and resource-limited settings.

As the fields of nanotechnology and microfluidics continue to evolve, such lab-on-a-chip technologies are ready to play a crucial role in the future of healthcare, ensuring accessible and efficient diagnostics for all.