Performance of force-compensated chemical sensors based on bisensitive hydrogels

Stimulus-responsive hydrogels have been investigated in the past for applications as transducers in chemical microsensors due to their excellent reversible swelling properties dependent on analyte concentration and their high energy density. However, the volume phase transition of hydrogels is also characterized by numerous disadvantages, such as viscoelastic creep and long settling times, which limit the competitiveness of hydrogel-based sensors. The force compensation approach with a bisensitive hydrogel is a measuring method that is intended to counteract these disadvantages by suppressing the volume phase transition of the hydrogel. This is done by using a bisensitive hydrogel transducer. The additional sensitivity of the hydrogel is used to apply a compensating stimulus in the opposite way, so that swelling or deswelling is actively counteracted. This work shows a sensor setup that uses this principle. Semi-interpenetrating polymer networks are used as a suitable bisensitive hydrogel. Sensor measurements reveal the numerous improvements of the sensor properties of the force compensation measurement method compared to the conventional deflection measurement method. In addition to a reduction of the response time of up to 68%, the extension of the measuring range, the suppression of hysteresis effects and further positive sensor properties with this new sensor setup are shown.