Team:Valencia/Hardware

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LEC activation

Our team prides itself in finding ways to link electronics to biology in a direct and innovative fashion. As a consequence we spent considerable time developing circuits and equipment allowing for quick and robust control of cellular physiology.

Direct electrical stimulation of cells

The first part of hardware design is an electronic amplifier capable of delivering range of voltages between 0 and 13 volts. It is based on an inverting amplifier (fig. 1). The input voltage comes from a sound card – a commonly accessible and low cost digital to analog converter. It allows us to control the waveform in an arbitrary fashion using a simple Matlab script.

The output is connected to platinum electrodes inserted into a buffer over either muscular, neuronal or yeast cells. We stimulate cells with delta-function pulses every second (or a few of them) to get continuous calcium influx. While muscular and neuronal cells respond to this kind of stimulus naturally, yeast will require some work. We hope that electrical stimulation of yeast could be obtained thanks to a heat-shock response (read more in modeling section) or reported calcium response to electroporation.

Electrostimulation for yeast

Our team has developed an electronic circuit capable of applying a voltage between 0 V and 24 V with a precision of 0.1 volts and during time intervals of up to 20 ms. to yeast cultures. This circuit will be used in a first stage to characterize the part BBa_K222000 or what we call LEC. In the characterization, this system supply the initial estimulation conditions for the cells for the different experiments very precisely, making the results obtained with the luminometer of great confidence.
The experimental device is composed of the following parts:
The first one is composed of a voltage source and two electrodes to stimulate the cultures.
The second one is an optocoupler performing the function of an electronic switch. It is composed of a led diode and a phototransistor. The phototransistor will allow to pass the voltage signal meanwhile the diode is illuminated.
The last part is the responsible of the fine control of the time period in which the voltage is applied. To do that we stimulate the diode with a PC sound card (it has a precision voltage signal that usually is transformed by buffers to reproduce sound) controlled by the function “sound” of the MatLab software.
The output signal of the soundcard was modified by a rectifier-filter and then passed through two operational amplifiers (one as a amplifier and the other as a tension buffer) in order to produce a very precise signal able to activate the optocoupler. The amplifiers are powered by 5 volts and ground, so we will have 5 volts at the output of the operational when the sound card is active, and 0 volts when idle.

This design allows for stimulating one channel. In order to make a working screen, we will need an array of electrodes connected to a multiplexer. See next section...

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 *'''Electrostimulation for yeast'''
-Our team has developed '''an electronic circuit''' capable of sending electrical impulses to yeast in a large range of voltages [0-100] V and high accuracy at the time of application of these, as they can reach a few milliseconds. As our initial design for neurons and muscles (which was more restricted in terms of voltages and powers), this circuit only serves '''to control a pixel independently''', but it can easily be '''controlled from any computer'''.<br> <br>
+Our team has developed '''an electronic circuit''' capable of applying a voltage between 0 V and 24 V with a precision of 0.1 volts and during time intervals of up to 20 ms. to yeast cultures. This circuit will be used in a first stage to characterize the part BBa_K222000 or what we call LEC. In the characterization, this system  supply the initial estimulation conditions for the cells for the different experiments very precisely, making the results obtained with the luminometer of great confidence.<br>
-In this circuit there are two well differentiated parts: ''the application part'', which highlights an adjustable voltage source and the electrodes through which we will stimulate our cells, and ''the control''.<br> <br>
+The experimental device is composed of the following parts:<br>
-Both are ''linked by an optocoupler'', which serves as the electronic switch. It consists of one LED (on the control) and a phototransistor (part of application), which lets flow current while the collector-emitter diode is lit. To stimulate the diode controlling the time of application accurately, '''we use the sound card''' (which has a high frequency) led by the "sound" Matlab function. <br> <br>
+The first one is composed of a voltage source and two electrodes to stimulate the cultures.<br>
-But the nature of sound is sinusoidal and therefore also the tension leaves the sound card, and we need to incorporate into our circuit ''a rectifier-filter control'', to ensure that our signal is as continuous as possible. Moreover, the tension that provides the sound card is insufficient to activate the optocoupler. This is the reason why we use ''two operational amplifiers'', one as amplifier and another simply as a voltage follower. The amplifiers are powered by 5 volts and ground, so we will have 5 volts at the output of the operational when the sound card is active, and 0 volts when idle.
+The second one is an optocoupler performing the function of an electronic switch. It is composed of a led diode and a phototransistor. The phototransistor will allow to pass the voltage signal meanwhile the diode is illuminated.<br>
+The last part is the responsible of the fine control of the time period in which the voltage is applied. To do that we stimulate the diode with a PC sound card (it has a precision voltage signal that usually is transformed by buffers to reproduce sound) controlled by the function “sound” of the MatLab software.<br>
+The output signal of the soundcard was modified by a rectifier-filter and then passed through two operational amplifiers (one as a amplifier and the other as a tension buffer) in order to produce a very precise signal able to activate the optocoupler. The amplifiers are powered by 5 volts and ground, so we will have 5 volts at the output of the operational when the sound card is active, and 0 volts when idle.
 [[Image: V_ElectroYeast.png|700px]]
 <br><br>
-This design only allows for stimulating one channel at once. While it is useful for proof-of-principle experiments, if we want to make a working screen, we will need an array of electrodes connected to a multiplexer. We are currently developing a device capable of stimulating tens of pixels at once.<br><br>
+This design allows for stimulating one channel. In order to make a working screen, we will need an array of electrodes connected to a multiplexer. See next section...<br><br>