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Sensitive and low-cost sensor structures using nanoimprint technology


Nanoimprint technology is a cost-effective method of fabricating nano-scale structures for large area surfaces, thus allowing the manufacture of nanostructures on an industrial scale. At VTT, this technology has been utilized in the development of a nanostructured sensor that makes use of the interaction between light and material.

Developed sensor structures permit the usage of both label-free and label-based sensing methods. Potential benefits include the use of disposable sensors for biosensing and environmental monitoring in which sensor regeneration between analyses is both complicated and expensive.

The sensor contains a polymeric optical waveguide structure where the light travels both within the polymer and outside it in a nanometre-sized slot. The electrical field of the light is amplified inside the slot, making the structure sensitive to detect the changes in the surrounding liquid. The sensor's response to the changes in the liquid's refractive index and surrounding temperature was examined by utilising planar Young interferometer structure. Typically, the reference arm of the Young interferometer is protected and only the sensing arm detects the changes of the surrounding material. With the developed sensor structure, utilizing the slot waveguide geometry in the sensing arm, both reference and sensing arm interact with the surrounding material. Therefore the developed sensor structures were able to compensate efficiently for the measurement drift caused by changes in environmental temperature.  

The sensors were fabricated with nanoimprint technology by replicating the sensor structures on deformable and curable polymer. Polymers as a material are very attractive for sensor applications, since they have high transmission at visible wavelengths, their surface can be functionalized and they are the biocompatible. Moreover, the used polymers can tolerate temperatures up to 250°C, and they are also transparent at commonly used data communication wavelengths, which opens up the possibility of utilizing them in data communication applications.

The results of the study were published in a doctoral dissertation, including several articles in recognized journals. 

Dissertation as a pdf
Polymeric slot waveguide interferometers