A remote query glucose dosimeter based -on magnetostatic coupling

Magnetically soft tbin film elements, see Figure 1, are bonded to a polymer layer that is made to swell in response to glucose concentration. The dosimeter design consists of four triangles, initidly spaced 50 )un apart, arranged tn form a 12 mm x 12 mm square with the triangle tips centered at a common origin. As the polymer size changes so does the distance between the magnetic elements and hence tbe magnetic domain structure per magnetostatic coupling. The sensor is placed within a lime varying magnetic field of an intensity sufficient to switch the magnetization vector of the collective magnetic elements comprising the dosimeter. The magnetic flux changes generated by the periodic magnetization reversals can be detected as a series of voltage spikes in suitably lofated detecting coils. Concentration levels of the chemical anal@ can be related to the ampliok of the d e w voltage spike that the time varying flux generates [l]. Figure 2 shows the voltage spike amplitude as afunction of element spacing for tbe 'split square' design shown in Fig. I ; window pane smctures have also been used with success. The sensing principle is general and can be adapted to sense a variety of analytes by appropriate polymer design. Since the sensor is monitored through changes in magneoc flux no physical connections are needed to obtain sensor information.