Chips Radiofrequency-Tagged Microreactors

A transceiver controlled by a computer is used to interrogate and receive the ID code of each RF tag. The transceiver antenna transmits a specially modulated, 125 kHz electromagnetic field. This field is of very low energy and not harmful. When an RF tag is held within about 1 cm from the transceiver s antenna, energy is picked up by the RF tag s antenna. A rectifier in the chip converts this energy to microwatt levels of DC power, which is enough to power-up the logic circuitry on the chip. In a very real sense, the RF tag is similar to a crystal radio (which does not require an external power source), except that the device serves as both receiver and transmitter. It is self-contained , in that the chip uses no internal batteries and has no external metallic connections. 

A synchronization signal modulated onto the transceiver s signal allows the chip to respond with its ID code (a serial sequence of ID bits) and error-checking bits. The time elapsed between placing the chip on the transceiver and seeing the ID code on the interfaced computer screen is about 0.5 s. 

How this works in practice is detailed as follows. After a compound has been identified for which several hundred to several thousand derivatives would be of value, a synthetic route is chosen that (i) permits linkage to a solid-phase support (ii) utilizes reaction steps that appear possible to optimize to 90% yield and (iii) affords reagents in each step for which desirable variants can be purchased (or, less optimally, can be made trivially). In the synthesis itself, one of the significant advantages of the microreactor approach becomes evident one can use standard laboratory glassware and equipment to accomplish the library synthesis. There is no need for the automation of liquid-handling steps, and indeed no need for automation at all until rather large libraries are desired (vide supra). 

For the second reaction step, every MicroTube needed to be reacted with an identical reagent, so one reaction was carried out with all 432 MicroTUbes, after which they were washed thoroughly. For reaction Step 3,54 (18 x 3) MicroTubes were placed into each of eight flasks computer software permitted us to read the RF tag of each MicroTube and know the flask 

4 Tubes and Cubes, Chips and Tips Tools for Solid-Phase Organic Synthesis 

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