Digital Microfluidics Control System II

P15610

Previous state - The previous control system is not self contained and uses a class AB amplifier which makes the system large and nonmodular.

Desired state - A fully enclosed control system that efficiently operates the DMF chip while providing accurate feedback.

Project Goals - Make key improvements to functionality of control system, and complete all assigned deliverables.

● Repeatable, consistent droplet motion.● Durable, lightweight, modular design.

Constraints - Use provided DMF chip, control fluid droplets using electrowetting, use DI water as test fluid, ensure compatibility with peripheral hardware and GUI.

Phase One: Problem Definition

Problem Statement

Phase One: Problem Definition

Engineering Requirements

Phase One: Problem DefinitionDropBot

Phase One: Problem Definition

Functional Decomposition

Phase Two: Subsystem Identification

System Layout

Phase One: Problem

Definition

Morphological Chart

Phase Two: Subsystem Identification

Original CAD Models

Phase Two: Subsystem Identification

Original External Design

Components:3 Enclosures and Lid1 Fan and Fan GuardElectrical Ports: USB, BNC, 40 pin connector, Power

Vent Grommets

Phase Three: Design and Testing

Output Board: PCB layout

Phase Three: Design and Testing

Output Board: PCB layout

● Takes amplified signal from amplifier chooses which pin on DMF chip to apply high voltage

● Consists of:o HV Solid State Relayso Shift Registers (Load pin positions to apply

voltage to)o Control Mechanism (ATMEGA)

Phase Three: Design and Testing

Output Board: Functionality

Phase Three: Design and Testing

Output Board: Functionality

ATMEGAShift

Register

Shift Register

Off Board

40 HV RelaysDMF Chip

Phase Three: Design and Testing

Input Board: Functionality

Phase Three: Design and Testing

Input Board: Functionality1pF: steady state voltage of 29mV

200pF: steady state voltage of 5.00V

Rise time: <10ms

Phase Three: Design and Testing

Input Board: Functionality60pF: steady state voltage of 1.693V

61pF: steady state voltage of 1.720V

Granularity: 27mV/pFor: 5.5 q-

level/pF

-Total simulated current draw: <25mA

-Noise: input filter to buffer limits frequency generator noise

-Large capacitive loading: Zener diode limits output (below)

-Output noise: two-stagelow-pass filter

Phase Three: Design and Testing

Input Board: Functionality

-Absolute values of measured capacitances ranged from 30pF to 170pF

-Capacitance changes over time in the minutes

-Capacitance differences sub-1pF

Phase Three: Design and Testing

Input Board: Previous Data

Graphs from Dr. Michael Schertzer “Automated detection of particle concentration and chemical reactions in EWOD

devices”

Phase Three: Design and Testing

Input Board: PCB Layout

-Input Board was tested using the designed circuit and outputted the following waveform before full-wave rectification

-This demonstrates that the signal is voltage-varying and can demonstrate changes in magnitude

-Phase detection remains untested, however the preliminary circuit was promising

Phase Three: Design and Testing

Input Board: Experimental Output

Phase Three: Design and TestingSignal Generator: PCB Layout

Phase Three: Design and TestingSignal Generator: PCB Layout

-(+)9 V p-p from signal generator amplified to 120 V p-p between ~100 - 100kHz

Phase Three: Design and Testing

Amplifier Functionality

-Simulated with a 600uH Resonant Converter Transformer

Phase Three: Design and Testing

Amplifier Functionality

-Breadboarded setup of amplifier design

Phase Three: Design and Testing

Amplifier: Preliminary Design

-Output waveforms at 10kHz and 100kHz respectively

Phase Three: Design and Testing

Amplifier: Preliminary Results

Phase Three: Design and Testing

Amplifier: PCB Layout

Phase Three: Design and Testing

Fault Detector: PCB Layout

Phase Three: Design and Testing

Indicator: PCB Layout

- Cosel +/- 15 V DC @ 1.7A- Cosel +5 V DC @ 2A

Phase Three: Design and Testing

Power Supplies

Phase Three: Integration

Machining of Enclosures

Phase Four: Final Design

Phase Four: Final Design

Phase Four: Final Design

Phase Four: Final Design

Performance vs. Requirements

Housing● 10 pin ribbon cable connector● Protective paint coating

Input Board● Purchase DropBot input board or modify existing software to

work with current boardAmplifier● Modify design to use BNC connector instead of SMA

Power Supply● Switch to using power supply from P15611

Opportunities for Future Work