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In many disease treatment processes, measuring brain pressure is essential. However, current methods such as external ventricular drainage (EVD) have issues such as infection risks and tissue damage. One approach is using a flexible PDMS neural probe with adjustable hardness containing low-melting-point liquid gallium to minimize damage to the brain. The long- term goal of the research is to develop a brain pressure neural probe with adjustable hardness. The objective of this study is to develop a flexible pressure sensor that can be integrated into the neural probe.
The study utilized semiconductor fabrication techniques to create piezoresistive pressure sensors and tested their resistance changes. The key innovation was the patterning of a conductive layer on PDMS. PEDOT:PSS was selected as the conductive material, and a coating technique suitable for PDMS was developed. The sensors will eventually be integrated into PDMS probes, becoming adjustable hardness brain pressure neural probes.
The research developed three types of flexible pressure sensors. The first sensor could measure resistance changes within the target pressure range (0.93-4.16 kPa) with a sensitivity of 0.0751 kPa¯¹. However, it had an oversized dimension, and when attempts were made to reduce its size, concentration gradient issues rendered it unfeasible as a pressure sensor.
The second sensor failed due to unexpected design and fabrication outcomes. The third sensor could measure resistance changes within the target pressure range, with a sensitivity of 0.0416 kPa¯¹. This sensitivity surpassed the previously developed piezoresistive pressure sensor in ourlaboratory by a factor of 26, successfully achieving the goal of enhancing sensitivity. However, there were flaws in the fabrication process, resulting in a low overall yield, leaving room for improvement.
Overall, the development of these flexible pressure sensors holds promise for breakthroughs in the field of brain pressure measurement. Nevertheless, further research and optimization are needed to realize their application potential, considering the current imperfections in the fabrication process.