A graphene integrated Kapton based flexible and highly sensitive plasmonic sensor for uric acid sensing

• As per our knowledge, this is the first flexible gold-coated Kapton-based SPR chip that fully replaces the gold-coated SF11 chip required in prism-based SPR sensors. The Kapton sheet is very cost-effective in comparison SF11 glass slide. • The use of a Kapton-based SPR chip promises to make it much more cost-effective in comparison to available SPR sensors. It is very easy to make a large area and flexible SPR chip using a Kapton sheet and we experimentally fabricated the chip of 5cm *10cm size. • Being flexible, this can easily be integrated with other nanophotonic devices. • The Kapton-based flexible SPR chip was also integrated with an N-layer graphene sheet to enhance its overall performance. • Using the flexible Kapton-based and graphene-integrated SPR chip, a uric acid sensor was developed to demonstrate one of its reliable applications. • Our developed uric acid sensor achieved the maximum sensitivity and limit of detection of 0.0810nm/μM and 11.450μM. This shows the best performance in comparison to other available and reported uric acid sensors to date. • Various controlled experiments were also performed to show the repeatability and selectivity characteristics of the sensor. • Being flexible by nature, GiF SPR chip presents its strong potential in developing portable and wearable biosensors for health monitoring applications. One of the most common natural waste products from diets high in purines is uric acid that is commonly filtered by human kidneys. Excessive consumption and delayed excretion of uric acid can disrupt blood uric acid levels. Abnormal variations in the normal uric acid level, which is less than 6.8 mg/dL, can lead to several health issues, including kidney stones and gout, etc. Available biosensors for uric acid detection have various issues such as low sensitivity, poor selectivity, shorter shelf life, and poor repeatability. Kretschmann configuration-based plasmonic sensors are prominent candidates for resolving the issues but the available plasmonic chips are expensive because of the involvement of special glass substrates, such as SF11 and BK7. This work mainly focuses on the replacement of SF11 glass sensing chips with a low-cost and flexible Kapton chip that shares the same refractive index as SF11, without compromising the sensor’s sensitivity. Moreover, to enhance the sensitivity of the Kapton based plasmonic chips, they were integrated with 1 – 3 layers of graphene. These graphene-integrated flexible (GiF) plasmonic chips were functionalized with uricase enzyme to develop molecule selective uric acid sensors for point-of-care detection. The developed GiF chips achieved a maximum sensitivity of 0.0810nm/μM and 0.0171nm/μM in the range 0 to 200μM, and 200 to 1000μM, respectively, with a limit of detection of 11.450μM for uric acid. Controlled experiments were also performed to demonstrate the repeatability, stability, and selectivity of the sensors. GiF SPR chip presents its strong potential in developing portable and wearable biosensors.