Microfluidic Impedance Spectroscopy System

First Design Review

Matthieu Giraud-CarrierKyra Moon02/08/2011

OverviewIntroduction

PurposeMotivationProduct Design

Project RequirementsDesign SpecificationsCustomer NeedsAlternate Concepts

Concept Selection and GenerationFundamental Design IssuesCritical ConceptsSchedule

Current and Future Work

Introduction—PurposeBasic goal: Build a microfluidic impedance

spectroscopy system. In other words -- build a chip with a small

channel which can be filled with fluids (primarily protein solutions) and then analyzed.

Introduction—MotivationMedical field – researchers can learn how

these proteins interact by observing the electrical properties of these solutions over a wide frequency range.Creating microfluidic systems out of

inexpensive materials would facilitate medical research by making it less expensive and easier to use.

Introduction—Product DesignThe final product: A chip of a few square

inches.Basic elements:

Waveguide runs through the chip and is terminated by an SMA connector on either side.

Microfluidic channel close to the waveguide (three copper lines) in the center of the chip.

Reservoir that ensures the channel will always be full during analysis. The user will also be able to connect to these reservoirs through a standard pressurized port.

Design SpecificationsBandwidth: 100MHz to 7GHzVolume of channel: 0.5mm X 1mm X 2cm (10uL)Accuracy (% repeatability): 5%Temperature stability: Within 1 degreeFinal outputs: Conductivity and Permittivity (from S-Parameters)Develop a numerical model for the waveguide (Sensitivity measures

for changes in permittivity and conductivity)Interface between Network Analyzer and Plotting Mechanism (GPIB,

LabView, Matlab)Materials: Standard PCB materials (FR-4, FR-2)Sufficient reservoir volume for a 5-minute testConnectors: SMA on board

Meeting Customer NeedsMetric # Need # Metric Units Marginal

ValueIdeal Value

1 1Operational frequency range

GHz 0.1 - 7 20Hz - 20

2 3 Volume of channel microliters <10 < 5

3 7,8 Accuracy % <5 <1

4 2 Temperature stability degrees 1 0.2

5 5 Evaporation time minutes 5 10

6 4,9Familiarity of hardware (connectors)

Subj.3 5

7 6 Familiarity of software Subj. 3 5

8 10 Size of the device in2 2 <2

Block Diagram

A user selects the liquid to be analyzed Liquid is sent into the microfluidic channel through Nanoport connectors. The Network Analyzer gathers information from the chip (using standard

SMA connectors) An interface turns the raw data from the analyzer into useful information

for the user.

Alternate ConceptsUsing acrylic instead of PCB material.Using a waveguide perpendicular to the microfluidic

channel rather than parallel.Using a multilayer board to build the waveguide

without direct contact to the channel. Modifying the geometry of the channel and reservoirs

and having the waveguide go straight across the chipMaking the waveguide run over the top of the channel

on the main copper layer.Using vias to avoid the 90 degree angle turns in the

copper lines. Using Prepreg to ensure no leakage.

Fundamental Design Issues

Material Selection: Decide what PCB type material will be optimal for our system.

Leakage Prevention: Design the board so that the protein solution can be confined properly to the channel.

Signal Path Geometry: Consider how to align the channel and waveguide and how to fit all the connections on the board.

Illustrations

Concept Generation: Material Selection

Concept Generation: Leakage Prevention

Concept Generation: Signal Path Generation

Schedule

Schedule – Critical PathDetermine how to

set milling depth on machine

Learn how to create vias and alignment holes

Make several prototypes

Have board made professionally

Schedule – CategoriesFirst category: learning how to use the devices and

software.Kyra – HFSS (modeling software), interfaces computerMatthieu – milling machine, CAD software , how to

create the boardsSecond category: physically creating the board

It takes time to bond the board, run leakage tests, and create several prototypes

Third category: waiting for outside sourcesArrival of parts, making the chip professionallyWe have little control over this category so we need to

order early

Current & Future WorkKyra is fine-tuning the current HFSS model.We will soon be getting the Prepreg and

running several tests to optimize bonding.Still learning how to use the camera system

on the milling machine.Using Network Analyzer to run preliminary

tests and gain intuition.

By next design review:All fabrication issues finalized and

optimized.Have a complete working model of our

system in HFSS.