1. TB or not TBPCR based Tuberculosis (TB) Detection on a Chip
Lael Wentland, Albert Nguyen, and Minjung Kim

2. Global Impact of TB
Mycobacterium tuberculosis
- ⅓ of world population infected with TB- latent or active
[1]

3. ● Leading killer for HIV+
→ Difficult to diagnose in HIV+ patients
● Can be multi-drug resistant (MDR-TB)
● Difficult for young children to give sputum sample
● More accurate test → power supply, labratory, skilled professional
Other Factors Complicating TB Diagnosis
[2]

4. Engineering: Global Health Challenges
Living on Under $10 a Day
● Consider cost for where the
diagnostic is needed?
● Who will be doing the test? - >
shortage of health workers
○ Majority of work done by
individuals with less training
● Where will this diagnostic be done? -
higher level hospitals with electricity
● At what stage of the disease will people be
tested?- > ideally earlier
[3]
[2]

5. Method Pros Con
Culture ● the gold standard!
● allows genotyping of the
bacteria
● susceptibility testing
● prolonged time to result ( > 2 weeks)
● high cost with delayed diagnostics
● difficult to obtain patient samples
● $30 per test [5]
Acid Fast Stain ● rapid detection ● inadequate sensitivity/specificty
Interferon Gamma
-Release Assays
(IGRA)
● tests can be done in less
than 24 hours
● requires single patient visit
● need fresh blood samples
● test cannot be given to patient who has
been recently ( < 4-6 wks) vaccinated
● cost $160-290 [6]
Skin Test • Easy to administer ● cost around $55 [6] per test
Traditional PCR
PCR
● High sensitivtiy and
sensitivity
● Rapid detection time
● No transport requirement
● Allows detecton from non
invasive species
● Potential contamination
● Unable to assess viability
● Limited ability for genotype and
susceptibility testing
● $ 5-10 [7]
Current Diagnostic Methods for TB
Adapted from [4]

6. Final Clinical Diagnosis/Method Mycobacterial
Culture
PCR
Tuberculosis 19 Positive 10 Positive
8 Negative
1 Uncertain
14 Positive
5 Negative
Non-tuberculous
Mycobacterial
Infection
6 Negative 3 Positive
3 Negative
6 Negative
Nonmycobacteri
al infection
33 Negative 29 Negative
4 Uncertain
33 Negative
Uncertain 2 2 1 Positive
1 Negative
Side by Side Comparison of
Mycobacterial Culture and PCR
Sensitivity = true positives/(true positive + false negative)
Specificity = true negatives/(true negative + false positives)
[8]

7. Why use microfluidics for PCR?
● Portable
● Cost-effective
o does not require trained staff or
infrastructure
● species concentration can be
regulated in space and time
● quick and uniform heat and mass
transfer because of the high surface to
volume ratio
● increased speed and automation
opportunities that can potentially
reduce contamination
[12]
[11]
[10]
[9]

8. General Constraints
● Reach and hold 98C
● Material that will be heated by
PID controller
● Pass FDA 510(k) inspection
Global Health
Constraints
● Low cost
● Able to function in a variety
of environments-durable
● Easy to use and minimal
electricity
● Quick or immediate results
● Local Materials used
whenever possible**
+

9. ● PID Controller:
○ must not deviate more than 0.5
Celsius from the set temperature
once it is reached
○ heat evenly throughout the resistor
○ minimize overshoot
● Be a more accurate TB diagnostic tool
than the ones currently available
○ sensitivity & specificity >= 95%
● Process patient sample in 1-2 hours
● 0.22 mm width with depth of 0.1 mm
● Cost < $9 per test
Specifications
[13]
[10]

10. Design
● Glass chip with etched channels
o Smooth curves
● Silicon Bottom
o High Conductivity
● 3 Thin-film Platinum heaters
o PID Controlled
● Cooling element unnecessary
Inlet
OutletTop View
Thin FIlm Platinum
Heaters/Sensors
Cross Section
Etched Glass Layer
Silicon Layer

11. How it Works
1. Sample with primer, nucleotides, and polymerase is fed into inlet
2. Enters Denaturation region ~ 95 C
3. Enters Annealing region ~68 C
4. Enters Elongation region ~72 C
5. Repeat
4
3
2
5
1

12. PID Control
● Run current through temperature sensitive platinum film
o Temperature detected as voltage drop
● PID controller finds error between set temperature and
detected temperature
● Converts error to duty cycle in heating film
● For quick response: kp = high
● For stability: ki = low, kd = high
[14]

13. PID Control: Results
● kp = 300, ki = 1, kd = 20
● Operating range not as narrow as desired
o Instrument limitations
● Overshoot and the steady state error reported 0.7 ◦C and ±0.1 ◦C,
respectively
User Input: 28 C
Operating Range: 27.5 - 29.5 C
User Input: 50 C
Operating Range: 48.5 - 52

14. Building and Testing Prototype
[11]

15. Testing
● Perform PCR with conventional methods and with chip then compare
results
Criteria for Success
● Reaction time must be shorter than with conventional method (~2.5 hrs)
● Operating range of +/- 0.5 C
● Cheap to make/use (< $9)
● High Specificity
o Prevent false negatives

16. Future Work
● Address contamination by
adding additional purification
chip
● Test on other disease
o viral, genetic, etc.
● Increase scale of production
o Plasmid production
● Test with better instruments with
higher sampling frequency

17. References
[1] "Global Tuberculosis Report 2014." WHO. Web. 7 Mar. 2015.
[2] TB Facts." Team:Paris Bettencourt/Human Practice/TB Fact. IGEM. Web. 7 Mar. 2015.
[3] "The New Worldmapper." Worldmapper: The World as You've Never Seen It before. The
University of Sheffield, 3 Jan. 2012. Web. 6 Mar. 2015.
[4] Yang S and Rothman RE. PCR-Based Diagnostics for infectious disease: uses, limitations, and
future applications in acute-care settings.
[5] Mueller DH, Mwenge L, Muyoyeta M, et al. “Costs and cost-effectiveness of tuerculosis cultures
using solid and liquid media in a developing country.” International Journal of Tuberculosis and Lung
Disease. 2008 Oct; 12(10):1196-202.
[6] de Perio MA, Tsewat J, et al. “Cost effectiveness of interferon gamma release assays vs.
tuberculin skin tests in health care workers.” JAMA Internal Medicine. 2009 Jan 26;169(2):179-87.
[7] Scherer LC, Sperhacke RD, Ruffino-Netto A, et al. “Cost-effectiveness analysis of PCR for the
rapid diagnosis of pulmonary tuberculosis.” BioMed Central Infectious Diseases. 2009, 9:216.
[8] Salian NV, Rish JA, Eisenach KD, et al. “Polymerase chain reaction to detect Mycobacterium
tuberculosis in histologic specimens.” American Journal of Respiratory and Critical Care Medicine
1998. Oct;158(4):1150-5.
[9] Shin YS, Cho K, Lim SH, et al. PDMS-based micro PCR chip with Parylene coating. Journal of
Micromechanics and microengineering. 2003. June;13:(5):768-774.
[10] Kim J, Byun D, Mauk MG, et al. “A Disposable, Self-Contained PCR Chip.” Lab Chip. 2009 Feb
21; 9(4):606-612.

18. References (continued)
[11] Schneegass I, Brautigam R, Kohler JM. “Miniaturized flow-through PCR with different template
types in a silicon chip thermocycler. Lab Chip. 2001 Sep;1(1):42-9.
[12] Oblath EA, Henley WH, Alarie JP, et al. “A microfluidic chip integrating DNA extraction and real
time PCR for the detection of bacteria in saliva. Lab Chip. 2013 Apr 7;13(7):1325-32.
[13] Yoon DS, Lee YS, Lee Y, et al. “Precise temperature control and rapid thermal cycling in a
micro-machined DNA polymerase chain reaction chip.” Journal of Micromechanics and
Microengineering. 2002 Oct; 12(6): 813-823.
[14] "PID Control." PidHingeController. Tin-man, 5 Apr. 2012. Web. 6 Mar. 2015.
<https://code.google.com/p/tin-man/wiki/PidHingeController>.