Analyte-triggered solution-to-gel phase transitions have the potential to be used in simple, low-cost indicators and diagnostic devices. The principle advantages of these responsive materials, compared to colorimetric and fluorescent materials, are that the yes/no signal is unambiguously detected by sight. These gelation-based sensors can be tailored to respond to a diverse array of stimuli, including heat, light, and chemical or biological analytes, and may provide a robust and inexpensive platform for practical sensing applications in both developed and developing countries.
Over the last four years, we have reported several gelation-based sensors for the detection of nitric oxide, mercury ions, triacetone triperoxide and proteases. In each example, the response is a "yes" or "no" to the presence of analyte. These sensors would be more useful if they could also determine the amount of analyte present. Therefore, our recent efforts have been focused towards the development of quantitative gelation-based sensors utilizing several different methods, including a piezoelectric sensor, a wireless magnetoelastic sensor, and microrheology. The overall strategies involve monitoring changes in viscosity during gelation and correlating this data with the analyte concentration.