1. Introduction Automation of laboratory experiments can save time and energy as well as improve results [1,2]. When automating experiments using high cost equipment such as diffractometers or laser sources it is often useful to prototype the set up; this aims to prevent damage to both the equipment and the users when applied to the actual system. In this project we propose a system of building these prototypes using LEGO TM and controlling it via a standard message brokering system. The message broker used in this project is the IBM TM Microbroker, part of the WebSphere software range [3]. This is a publish/subscribe application; data producers publish a message to the Microbroker on a given topic (the content typically as XML) and data consumers subscribe to a topic, when a message is published the Microbroker determines which subscribers should receive the message. The Microbroker acts as middleware in the system, keeping the producers and consumers independent. As these parts are independent, any software publishing control messages can be used in both the prototyping and deployment stages without modification as it will only be communicating the message broker. Similarly if the software generating the control messages is changed the consumer software will continue to work, this is shown in Fig. 1. The LEGO TM Laboratory: Laser Induced Fluorescence Stephen Wilson, Oliver Birch & Jeremy Frey* School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK; sw1703@soton.ac.uk Acknowledgments This project is funded by the EPSRC and the Nuffield Foundation. Oliver Birch would like to thank the Nuffield Foundation and Excitec for organising and funding his placement opportunity at the School of Chemistry, University of Southampton. References 1.FJA Cardoso. A universal system for laboratory data acquisition and control. IEEE Transactions On Nuclear Science, 47(2, Part 1):154{157, APR 2000. 2.J.M. Robinson, J.G. Frey, A.D. Reynolds, B.V. Bedi, and A.J. Stanford-Clark. From the laboratory to the mobile phone: Middleware for laboratory data acquisition using the publication subscribe model. In e-Science 2005, 2005. 3.Andy J. Stanford-Clark. Integrating monitoring and telemetry devices as part of enterprise information resources. WebSphere MQ Integrator, March 2002. 4.Java for LEGO Mindstorms. Lejos. [web page] http://lejos.sourceforge.net/. [Accessed 17 September 2009]. 5.Labjack - US/Ethernet based data acquisition and control. Labjack. [web page] http://www.labjack.com/. [Accessed 17 September 2009]. Fig. 1. The message pathways for control, execution and output messages Why use LEGO TM LEGO TM has been suggested as a prototyping mechanism as it is relatively inexpensive while providing a large, if somewhat inaccurate, array of sensors and actuators. A typical Mindstorms TM kit contains three actuators, light sensor, touch sensor, sound sensor and ultrasonic sensor with others available to purchase. Its ease to assemble and disassemble structures quickly allows for fast prototyping and reuse of components. Modifications are also easy to make when potential problems have been highlighted through testing. The NXT controller was flashed with the LEJOS [4] software. This is a version of a Java Virtual Machine which has been optimised to run on the limited resources of the NXT controller. The framework allows for software to be developed to run both on the controller in a stand-alone mode or on a desktop environment sending commands via USB or Bluetooth. In this project the desktop environment was used allowing the software to communicate with the message broker. The experiment The apparatus prototyped will be that used for a laser induced fluorescence experiment. A laser beam will travel through a solution of sample of known concentration. The photons of the beam will excite molecules within the solution to a higher energy state, a portion of this energy will be lost through decay to a lower energy state. The remainder of the energy will emitted as fluorescence (at higher wavelength therefore lower power) as the molecule relaxes back to its resting state. As the beam travels through the solution fewer photons will be available to excite the molecules, therefore there will be a decay of fluorescence relative to distance through the solution. This rate of decay can be used to determine the extinction coefficient ( ɛ ) of the molecule using the Beer-Lambert law, shown in Equ. 1. Log (I/I 0 ) = - ɛ cl Where… I = Intensity of detected light I 0 = Intensity of incident light c = Concentration l = Path length ɛ = Extinction coefficient Equ. 1. the Beer-Lambert Law Experimental setup The experiment required a light sensor to periodically take measurements while travelling parallel to the laser beam. This was constructed through LEGO TM as a track a motor would travel down, measuring its distance travelled via the tachometer. The light sensor was connected to the motor at a fixed height equal to that of the laser beam. The laser source used was a Class 3R 532nm 5mW laser pen. The solution was contained in a square beaker to minimise refraction effect from curved glass. The experimental setup can be seen in Fig. 2. Fig. 2. The LEGO TM prototype for the laser induced fluorescence experiment (a) The experimental setup (b) The induced fluorescence showing reduction of emission from left to right Controlling software As the system interacts with external devices such as mobile phones via the message broker, when launched the required connections are made and it enters a waiting state. When a message is received the experimental parameters, such as motor speed, distance to travel and number of repeats, are extracted from the XML. These parameters are then used to generate the relevant commands for the NXT controller. While the motor is travelling, readings from the light sensor are taken every 10ms and referenced to the tachometer reading, these are written to a temporary CSV file. The experiment is repeated the required number of times before switching the laser off, a final run is completed to determine the background reading. On completion a message is sent to the message broker informing clients the software is ready to begin again. A secondary message is sent to another client which processes the CSV file. This is written to a MySQL database where the data can be interpreted by output devices such as plotters or displayed through a web page. Results and Conclusions The experiment was run with a 5.41µM solution of Rhodamine 6G, a fluorescent laser dye. 12 runs were completed and the average intensity for each tachometer reading was calculated. Each reading was background reduced and plotted to give the graphs shown in Fig. 3. From this the extinction coefficient was calculated to be 149x10 3 mol dm -3 cm. Compared to the literature value of 116x10 3 mol dm -3 cm this is relatively accurate, considering the equipment used. Although the dye was specifically selected as it would work well, it has been shown that LEGO TM can be used to develop prototypes for chemical apparatus. LEGO TM has allowed for fast design, implementation and modification at minimal cost. Due to the limitation of the available sensors not all apparatus can be simulated in this way, although with network data acquisition cards such as the LabJack [5], off the shelf sensors can be implemented with minimal effort. The use of the Microbroker has allowed for a number of input and output devices to be developed to interact with the experiment while remaining independent of each other. The control software can also be incorporated in the full experimental setup as it is independent of the device it is controlling, reducing the deployment time of the equipment. Fig. 3. Results from a 5.41µM solution of Rhodamine 6G