B1.2 - Hydrogel-Based Biochemical Sensors

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
B1 - Piezoresistive Sensors
M. Günther, G. Gerlach, T. Wallmersperger - Technische Universität Dresden (Germany), F. Solzbacher, P. Tathireddy, J. Magda, G. Lin, M. Orthner - University of Utah, Salt Lake City (USA)
211 - 215


With the rapid development of micro systems technology and microelectronics, smart electronic systems are emerging for the continuous surveillance of relevant parameters in the body and even for closed-loop systems with a sensor feed-back to drug release systems. With respect to diabetes management, there is a critical societal need for a sensor that can be used to continuously measure a patient’s blood glucose concentration twenty four hours a day on a long-term basis. In this work, thin films of “stimuli-responsive” or “smart” hydrogels were combined with microfabricated piezoresistive pressure transducers to obtain “chemomechanical sensors” that can serve as selective and versatile wireless biomedical sensors. The principle advantages of the piezoresistive sensor design are the following ones:

- the separation of the electrical sensor components from the analyte ambient, which significantly increases the long-term stability of the device and
- the usage of inexpensive micro fabricated silicon chips with highly sensitive and stable bending plates and mechano-electrical transducers.

The biochemical sensor containing a special biocompatible copolymer of acrylamide and 3-acrylamidophenylboronic acid with a sharp volume phase transition in the neutral physiological pH range near 7.4 can detect a specific analyte, glucose. This hydrogel shows volume increase with increasing glucose concentration because glucose binding favours the charged form of boronic acid groups. The sensitivity of hydrogels with regard to the concentration of glucose in solutions with physiological pH, ionic strength and temperature was investigated in vitro. The response of the glucose-sensitive gel was studied at different regimes of the glucose concentration change and at different temperatures for two sensor design variants. Sensor response time and accuracy with which a sensor can track gradual changes in glucose was estimated.
The influence of analyte-polymer interactions on the sensor response time is considered at the modelling of the swelling behaviour of metabolically sensitive hydrogels. The temperature characteristic of the sensor output voltage has been obtained and will be used for the calibration of the glucose sensors. The long-term measurements in this work have shown that the life time of piezoresistive biochemical sensors can be prolonged up to several months under harsh physiological conditions.