Sexually Transmitted Infections: -signiﬁcant burden to UK and worldwide healthcare system -area of priority for world health Current technologies mostly based on phenotypic characterization Methods for microbial genome analysis are available Nucleic acid-based detection is more speciﬁc and sensitive even if immunological-based detection is faster and more robustOUR CHALLENGE:Need of a reliable device able to perform very high sensitivity for small analyte volume tolerant and adaptive to varied environments
FOCUS of the Brunel group: develop a rapid, accurate microﬂuidic device for polymicrobial pathogen detection form complex matrices such as blood, urine or urethral swab samplesAttempt to penetrate into high risk groups such as youth and immigrant sectors who are reluctant to seek prompt primary care in the traditional settings PURPOSES: individual beneﬁts + incorporation into broadband and mobile communication systems
How the designed Electronic Control System look like? Set point + ε Sample Thermistor CONTROL - Biological system Peltier vs PWM Electronic control V ---> Tchip I R C V ----> Tamb Biological block represented as a single pole circuit
Temperature reading and control Calibration: TTC05 104 400 350 300 Resistance (KΩ) Thermo-resistance 250 200 TTC05 104 150 Exp.(TTC05 104) 100 y = 333,42e-0,045x 50 0 0 20 40 60 80 100 Temperature (°C)How to use it:+5V Thermistor 100K TTC05 104 3,5 y = 0,056x + 1,0305 3 2,5 Output Voltage (V) 2 1,5 TTC05 104 Linear(TTC05 104) 1 The voltage divider output is not 0,5 varying linearly with temperature, but 0 in a limited range of temperatures it 0 10 20 30 40 50 can be considered so Temperature (°C)
Arduino prototyping board: •ATMega2560 •Open-source software/hardware •Flexible •C Code •Bluetooth, WiFi, GPS, GSM functionality + 10 bit ADC converter Voltage divider output connected to ADC analog input CONVERSION TO A TEMPERATURE VALUE 1LSB corresponds to 0,087 degrees of sensitivity ---> good enough for our application!!
We can read the temperature.......But how can we get the temperature we need? How does this work? Peltier thermo-element •Device that utilizes the Peltier effect to implement a heat pump •Several thermo-couples connected together between the two plates •It does not generate heat or cold, it just transfers heat from one plate to the other
Check with the oscilloscope: is it actually working properly?V1 tV2 t V1(10%-dt) + (V1+V2)dt + V2(90%-dt) + 0*dt =V1 = V1*10% - V1*dt + V1*dt + V2*dt + V2*90% - V2*dt = t = V1*10% + V2*90%V2 t dt
We need to maintain a constant temperature...•Bang bang control ---> not precise; too long time response•Hysteresis control ---> not stable; unacceptable ripples•PID control ---> adopted solution! WHAT IS PID CONTROL? WHY PID CONTROL? AND WHY A SINGLE POLE CIRCUIT?
PID controlProportional-Integral-Derivative control: robust performance in a wide range of operating conditions functional simplicity Capable of manipulating the process inputs based on the history and rate of change of the signal it gives a more accurate and stable control method It consists of three basic coefﬁcients: proportional, integral and derivative, which are varied to get the optimal response Our project needs: •proportional control by applying pulse width to the heater •integral component to solve the “dead-band” problem •no need for derivative control The optimal Kp will allow a small overshoot, the other coefﬁcients are calculated using the table
Single pole circuit characteristics: 55 Experimental curve Gain& Ideal curve 50 60" y"="0,3177x"+"15,779" 50" Final&temperature&(°C)& 45 40" Temperature (°C) 41 40 30" Temperatures" 116.432 sec 20" Linear"ﬁ>ng" 35 10" 30 0" 0" 20" 40" 60" 80" 100" 120" τ Duty&Cycle&(%)& 25 0 200 400 600 800 1000 1200 1400 Time (s) It is reasonable to use Ziegler-Nichols method because it is justiﬁed by the theory about feedback control PI transfer function: U(s) = e·Kp + e·Ki/s
Program ﬂowchart START Variables declaration and pins setting-out Timer and LCD con guration Start Interrupt Put reagents 1 and 2Read the sensor value and into the chamberconvert into a temprature •Why? •What is their function? Set the magnets on and o Is the temperaturehigher than the set point? YES NO Wash the waste Turn the Peltier Turn the Peltier o on Put the sample into the microarray Print out the temperature Stop on the screen Interrrupt
What I achieved:•Laid foundations for a conscious and critical approach to a project•Study and project of the disposable cartridge•Temperature control•Programming microcontroller ﬁrmware•Tests and experiments to verify the effective functioning•Measure of magnets parameters•Tests to verify the effective role of the magnets in mixing Future work: Microﬂuidic network (reliable movement of precise volumes) Reducing processing times (fast diagnosis increases clinical utility) Biochemical Processes (developing protocols amenable to miniaturization & automation) Speciﬁc Detection (system indicating presence or absence of DNA) Full Automation (Sample-in to Answer-out)
Playing with the magnets Reagents Camera setup Magnet...They actually mix the liquids These are t wo videos