Group R14300 – Digital Microfluidics Peter Dunning Paulina Klimkiewicz Matthew Partacz Andrew Greeley Thomas Wossner Wunna Kyaw
Problem Statement • Need for point of care medical testing devices where access to conventional tests is restricted o Ex: Doctor’s Offices, Remote Areas, Battlefields • A solution must be portable and cheap
Problem Statement • Lab-on-a-chip devices are capable of miniaturizing and automating biological protocols. • Devices suited for commercial use have just started to be developed. http://2.imimg.com/data2/GK/EX/MY-920622/micro-biological-testing-250x250.jpg http://www.lionixbv.nl/technology/technology-microfluidics.html
Digital Microfluidic Devices - Electro-wetting Cross-section view of Digital Microfluidic device. Dotted line indicates the shape of the meniscus before actuation. Modified from [2] ● Array of electrodes which use the electrowetting effect to manipulate droplets. “Top view of flow on a ring structure” [3]
Voice of the Customer
Voice of the Customer
Functional Decomposition Much room for Little to no room Medium amt. of creativity for creativity room for creativity
Project Breakdown • Control System • Fluid Delivery System • Fabrication • Automation • User Interface • Packaging
Control System - Specs and Metrics Problem: Can an Arduino board be used to control a DMF device to the same or better accuracy as a NI PXI control system? What Do We Need? • Generate a sine wave • Amplify the wave to a large voltage (~90-110 Vrms) • Measure capacitance with a good resolution (~0.2pF) • Complete the protocol quickly (~30min) • Move/Merge droplets quickly (~100ms) • Split droplets quickly (~500ms) What Do We Know? • Benchmark: Dr. Schertzer completed these protocols at the University of Toronto using a National Instruments (NI) control system, a signal generator, and an amplifier
Control System - Potential Concepts Benchmark - Control System used in Schertzer et al 1. NI PXI System a. Signal Generator i. Voltage: 10Vp-p ii. Frequency: 10kHz b. Controller c. Matrix-Switching Device (4 inputs / 32 outputs) 2. Agilent 4288A Capacitance Meter a. Resolution to ~0.20 pF 3. Custom Amplifier a. Voltage: 90-110 Vrms
Control System - Potential Concepts Arduino Dropbot System in Fobel et al Control Board Signal Generator Board - Generates a sine wave - Controls is a shield for the • Voltage: up to 20 Vp-p Arduino Microcontroller • Frequency: (0.1-50)kHz Trek Model PZD700A High Voltage Switching Board Amplifier • Arduino is open source o firmware o pin mapping o board schematics - Droplet was found to • completely cover an electrode KiCAD Hardware designs • in 200ms Input Voltage: 0 to ±10 VDC available for Board designs • • Output Voltage: 0 to ±700 VDC 320 independent channels and is highly modular
Control System - Potential Concepts Arduino Dropbot System in Fobel et al Arduino Mega 2560 Microcontroller - Controls Signal Generator Board, High Voltage Switching Board - Can estimate drop position, velocity - Software Available: ● Arduino firmware ● C++ Software ● Microdrop Plugin • Arduino is open source o firmware o pin mapping o board schematics • KiCAD Hardware designs available for Board designs • 320 independent channels and is highly modular
Control System - Feasibility Potential Staffing Needed ● Mechanical Engineering ● Electrical Engineering ● Software Engineering ● Computer Engineering ● The Arduino Dropbot system used in Fobel et al paper was able to instantaneously measure droplet velocity, capacitance, and impedance in real time. ● Arduino has: a. Software: C++ software, Open source firmware b. Hardware: Microcontroller with board schematics, and pin mapping ● Dropbot has: a. Software: Open source firmware, Microdrop Plugin b. Hardware: KiCAD models to create the boards
Fluid Delivery System-HOQ
Fluid Delivery System-Specs and Metrics Problem: Is there a specific delivery system so that the desired volume of fluid can be extracted within the desired time? What We Need • Droplet to be extracted between .5s and 5s. • Droplet Volume must be within 3% error of desired volume. What We Know • Conventional Biological Protocols have been using pipettes and Syringes • Duke University have used Reservoirs in their DMF Devices.
Fluid Delivery System-Concepts • Syringe o .55 L ± .028 • Pipette o 1µL ± 4% • Reservoir o Volume from User Input • Plug-in Canister o Desired Volume can be extracted • Combination of These
Fluid Delivery System- Feasibility • Solutions o Reservoir system will allow us to easily dispense the fluids to the DMF device. Using together with Pipettes will allow us to accurately dispense the desired droplet volume. o Plug-in Canister can be programmed to dispense the right amount while easily detachable and portable. • Staffing Required: o Students in the Mechanical Engineering discipline o Students in the Industrial Engineering discipline
Fabrication- HOQ [10]
Fabrication: Potential Concepts Common Techniques:Photolithography and wet or dry etching (clean room) Solutions outside the clean room: • PDMS stamp used to transfer a pattern onto a gold surface • Desktop laser printer pattern transfer: directly onto sheet of polyimide • Permanent marker electrode array outline Dielectric: Saran wrap Hydrophobic coating: Rain-X
Fabrication: Feasibility Microcontact printing (microCP) [7] • PDMS stamp used to deposit patterns of self assembled monolayers onto a substrate • device capable of full range of operations: dispensing, merging, motion and splitting Formed from circuit board substrates and gold compact disks using rapid marker masking [8] ● procedure capable of producing devices with 50- 60 μm spacing between actuating electrodes ● saran wrap used a removable dielectric coating ● rain-x: hydrophobic coating ● able to move merge and split 1- 12 μL droplets Desktop Laser Printer Pattern transfer [9] • Droplet motion: comparable to performance on chips made by photolithography • ultrarapid: 80 chips in 10 mins
Automation - HOQ
Automation - Specs and Metrics Problem: Can a protocol be automated using existing computing methods and hardware? What Do We Need? • Data Storage (~0.5GB) • Send Signal • Receive Signals • Processor (>10kHz, ~0.5GB) • Motion Planning What Do We Know? • Many algorithm based computing solutions already exist, just must be tailored for this specific application
Automation - Potential Concepts How to compute: • Existing computer • On-board processor • Open-source system Function: • Inputs: state of each electrode, protocol • Process: compute necessary move, merge, mix & split instructions for a specified protocol • Outputs: signals to activate control system switches, error signal to the user interface, result
Automation - Feasibility Needed Available Solutions: Features: Data Storage Memory Card, HD, SSD, Peripheral networking, ROM cartridge Send Signals Analog signals, digital signals Receive Many ways to process signals.. Signals Processor Micro-processor, multi-core processor Motion Grid based algorithm, Sampling Planning based algorithm Each feature has many well known solutions. This project is determined to be feasible.
User Interface HOQ
User Interface - Potential Concepts LabVIEW Front Panel [4] -Computer program w/ visual display (i.e. LabVIEW VI) -Touchpad -Manual input (i.e. turn dials) -Remote communication (i.e. email) Example of “lab -LED indicators on a chip” [5] -Combination of these Handheld DMF device [6]
User Interface - Feasibility Technical Feasibility -Concepts for the user interface exist in many forms -Many existing DMF devices are able to accept instructions and output results via a user interface. -Example: RIT currently uses LabVIEW interface provided by National Instruments Staffing Requirements A few IE, ME, and EE students, possibly a CE as well
Packaging HOQ
Packaging-Concepts Minimizing Evaporation • Humidity sensing/control o Humidifier/hygrometer/controls • Temperature sensing/control o Refrigerator/thermometer/controls • Hybrid
Packaging-Feasibility Verify that size and weight constraints are met: Staff required: Several ME students, several EE students, possibly IE students
Questions/Areas of Uncertainty • How will environmental controls be implemented? • Chip form factor?
Next Steps • Confirm ER’s • Continue to refine HOQs • Examine resource and staffing requirements • Begin PRP development
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