From Smart Tags to Brilliant Tags: Advances in Drug Stability Monitoring

Nov 01, 2005
Volume 18, Issue 11


Figure 1. RFID Tags Monitor Time and Temperature
Most readers of this article are probably well aware of the initiative to incorporate RFID tags into standard drug packaging (Figure 1).6 This initiative is designed to detect counterfeit drugs and protect product integrity. RFID tags, which typically cost less than a dollar, clearly demonstrate that modern electronics are capable of putting an impressive amount of computing power and radio-frequency capability into a paper-thin and inexpensive label. RFID tags usually avoid the cost and complexity of needing an onboard battery by using a "passive" design that draws power from the energy provided by the RFID tag reader. Thus these tags are not powered when the tag is not being read. Although they are called "smart" tags, they speak only when spoken to. They are smart, but not quite smart enough.

Figure 2. Electronic Stability Monitoring
Instead of a "smart" tag that speaks only when spoken to, drug stability monitoring requires a "brilliant" tag capable of independent decision-making. A brilliant tag must be continually thinking and calculating, even when the tag is not being read. Ideally the brilliant tag will either visually display the drug status (good, not good) on a continual basis, or immediately transmit the drug status to the user when an RFID reader reads the tag.

Clearly for this to work, a brilliant tag must use an ultra-low-power microprocessor that is always turned on. This microprocessor must continually sample the ambient temperature and perform stability calculations using a sophisticated drug stability model. Figures 1– 3 illustrate how such a sophisticated drug stability model can work.

Drugs typically remain viable for several years. For this brilliant tag to be practical, it must have a tiny paper-thin battery, an economical price, and an ultra-low-power microprocessor that can run for several years off small amounts of power available from a tiny battery. Is modern electronics up to this task?

Figure 3. Stability Algorithm for Insulin
Fortunately it is. Low-cost, paper-thin batteries are commercially available. Paper-thin batteries produced by ultra-low-cost printing processes are available with dimensions such as a 39 mm x 39 mm x 0.7 mm (1.5 inches x 1.5 inches x .03 inches) thick battery (0.06 inches thick for a two-cell battery capable of delivering 3V). These batteries feature lifetimes of three years and a power capacity of 30 milliamp hours (mAh). More conventional coin-sized batteries are available for a cost of only a few cents each. Coin-sized batteries can deliver 220 mAh of current at 3V and last for up to ten years.

Suitable high-performance, economical, and ultra-low-power microprocessors also are available. For example, 16-bit microprocessors are available that run on as little as 0.8 microamps current and cost less than 50 cents.7 This 16-bit microprocessor has a computing capability that compares favorably with that of the original IBM personal computer, and would run for up to 3.4 years with paper-thin batteries, or more than 10 years from coin cell batteries. Less sophisticated, but still adequate 8-bit and 4-bit microprocessors are also available and cost less than 25 cents a piece.

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