Sensors based on sorptive-mechanical transducers for detection of physiological parameters according to the intramolecular compensation method

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The rapid detection of low concentrations of physiologically relevant species in the human body still poses major challenges in biomedical engineering. These parameters, which are usually present in solution, include thrombin, glucose, the pH value and various ion concentrations. However, the development of suitable microsensors, without which point-of-care diagnosis is hardly conceivable, always finds itself in the field of conflict between sensor miniaturization on the one hand and the three core characteristics of a sensor: sensitivity, selectivity and stability on the other.Stimulus-responsive hydrogels, which occupy a certain volume depending on a measuring species present in solution, can be used as sorptive-mechanical transducers in microsensors. The measured variable-dependent swelling pressure is then converted into an electrical output signal by a mechanoelectric transducer, e.g. a piezoresistive pressure sensor. However, these miniaturized hydrogel-based sensors have long measuring times due to the volume phase transitions. Recently, the measuring method of intramolecular compensation was presented to counteract these disadvantages of hydrogel-based sensors. The aim of the measuring method is to suppress the swelling of the hydrogel in the sensor. By staying in the swelling equilibrium, tedious swelling processes are counteracted and the sensor properties are drastically improved. Thus a reduction of the measuring time by up to 70% could be achieved. Furthermore, the compensation method allows to extend the measuring range and to counteract viscoelastic creep. To pave the way for a wider range of applications, a fast and reliable manufacturing process for the fabrication of compensated sensors is of special interest. The hydrogel sensor should also become biocompatible. The research group of Prof. Solzbacher (University of Utah) is leading in the development of hydrogel-based sensors, which use a polyimide-based cantilever as swelling pressure transducer and thus offer biocompatibility.The aim of the research project is to combine the measuring method of intramolecular compensation with the comparatively simpler and biocompatible hydrogel sensors of the Solzbacher group. At the same time, further compensatory hydrogels with physiologically relevant sensitivities (e.g. glucose) are to be developed. In the long term, this should pave the way for reliable, miniaturized biosensors that can be integrated into catheter tips, for example, to measure dissolved substances (e.g. anesthetic gases) directly in a patient's blood and in almost real time.