Presentation Overview

Enzyme BiosensorDetection of glycerides in biodiesel1Team Members:Ben WilsonMatt YourekMegan TempletonMentors: Dr. Tom Hess Dr. Dev ShresthaClient: Dr. Dev Shrestha

Presentation OverviewOpportunity Statement

Current Testing Method

Product Specifications

Housing Design

Circuit Design

Membrane

Experimentation

Experimental Design

Parameter Measurements

Results

RecommendationsOpportunity StatementDesign, fabricate, and test a handheld biosensor that uses a modified pH meter combined with an immobilized enzyme electrode to detect the amount of free and total glycerol in a sample of biodiesel.3

Current Testing MethodCurrently biodiesel makers use a gas chromatograph to measure the amount of glycerol within their biodiesel. While the GC provides a very accurate measurement, it is a time consuming process to prepare and test a sample.4

Product SpecificationsLight weight total weight of less than 5lbs

Small have a footprint smaller than half a sheet of paper

Durable able to withstand drops and bumps

Reusable can test multiple samples with one membrane

Fast easily calculates concentration percent in seconds

Simple minimal buttons and good user feedback

Accurate Consistent voltage signal for each sample

Easy to Calibrate a single button push resets reference voltageHousing DesignFabricated using the Mechanical Engineering Department ABS plastic rapid prototype printer

3/16 wall thickness

1 x 6 x 3.5 internal space

Six attachment points

Separate battery compartment

Circuit board attachment points

Circuit DesignMajor Components

Op Amps

RC Filter

Arduino UNO

Circuit DesignLM741CN

Simple operational amplifier

Forces voltage signal to be positive by adding a constant voltage to the measured signal

AD623AN

Variable gain operational amplifier

Amplifies voltage signal so small changes can be recognized by the ArduinoCircuit DesignRC Filter

Uses a resistor and a capacitor in series to filter the signal

Removes high frequency signal noise added during amplification

The cutoff frequency (Hz) is calculated using the equation

Circuit DesignArduino UNO

Registers user input through buttons

Reads voltage from probe and assigns bit value to corresponding variable

Blinks LED to verify that a button has been pushed

Writes valuable information to LCD screen

Processes input voltage from probe by removing the added voltage and converting to concentration percent

Circuit Design

Circuit DesignThe Biosensor was calibrated using a DC voltage source and a digital multimeter

A line was then fit to the data using the Matlab fitting tool

The calibration equation was then programmed into the Arduino, so the true signal voltage is displayed

MembraneInitially going to test three types of membranesPVAPVDFWater emulsion

MembraneMembrane Failure

In the beginning the membrane easily degraded

Then even the thinnest layers of membrane were too thick to record accurate measurements

Determined to add lipase directly to solution

ExperimentationRan 32 experiments testing four variables:

Feedstock

Lipase

Temperature

Soap

Feed - Oil - Biodiesel Temp. - 20C - 40C Lipase - 20 mg - 10 mg Soap - 1 ml - no soap

VariablesANOVA - Identify significant variables

Regression Analysis - Identify optimal combinations

Calibration

Experimental Design Initial pH

Initial mV

Final pH

Final mV

pH

mV Point Measurements:Time-based Sampling:Parameter MeasurementsSignificant Variable: Optimal Combination:Feedstock 20 mg lipase, 20C, 1 ml soapResultsSampleFeedDimensionless ValuemV1Canola Oil015.92Canola Oil08.0330 min. Biodiesel0.546.7430 min. Biodiesel0.549.0560 min. Biodiesel 191.1660 min. Biodiesel 1101.0RecommendationsConstruct calibration curve from biodiesel samples with known concentration of total glycerides. True concentration is determined by gas chromatography (GC)

Validate curve with GC analysis

Gain better understanding of reaction mechanism driving the pH change

Determine membrane composition and thickness having the least impact on probe sensitivity

Questions?