Example Applications - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 382

are occurring during loading, and how busy the individual loading points are. The
rapid collection of goods from the stores is important because customers, who are
mainly pharmacists, expect the consignment to arrive on time and be complete. This
can only be guaranteed by a technically infallible order picking procedure (Sander and
Mollik, 1997).
13.11 Medical Applications
The ability of passive transponders to operate reliably for years without their own
power supply — which may be susceptible to failure — predestined this technology
for applications in human medicine .
Glaucoma is a condition in which increased interocular pressure (IOP) at first causes
a narrowing of the field of vision, and ultimately results in complete blindness. The lat-
est research has shown that interocular pressure is subject to sharp diurnal fluctuations
and that not only the absolute pressure, but also the pressure fluctuations, significantly
influence the risk of blindness (ullerich, 2001). Therefore, the continuous measurement
of the interocular pressure under normal conditions and in the patient's normal envi-
ronment is necessary to improve understanding of the progression of the condition and
facilitate an individual programme of treatment (Bogel and Niederholz, 2001). This is
in contrast to the normal practice of measuring IOP exclusively during surgery hours
with the aid of a tonometer.
In patients with a cataract, the natural lens is removed from the eye and replaced by
an artificial interocular lens . This prompted the idea of integrating a full transponder,
i.e. a microcoil and a transponder chip with an integral capacitive pressure sensor, into
the haptic of such an artificial intraocular lens. Figure 13.53 shows such a transponder
unit after casting in PDMS (polydimethylsiloxane), a soft silicon normally used for the
manufacture of artificial lenses.
The external diameter of the microcoil is around 10.3mm and the internal diameter
7.7mm. For the optical part of the lens 5mm is specified. The microcoil is manu-
factured on a flexible polyimide foil (Ullerich, 2001; Ullerich et al. , 2000, 2001a,b)
Figure 13.53 Transponder unit after casting into an artificial intraocular lens made of silicon.
(reproduced by permission of IWE1, RWTH Aachen, D-52074 Aachen)