Paper Analytical Devices

Nopad Timeline




Collecting and testing medicine takes so long

that the bad products are no longer in the market

Pad Comparison Maybe










Find fakes faster with PAD testing!

PADs are robust field screening tests that work for many different medications. The current card design is a complete lab on a piece of paper--the user does not need to add anything other than the medicine to be tested and water. The test card stores the reagents, mixes them in the correct order, and brings them to the drug sample. The user does not need any instruments or supplies, other than the test card itself.

Chemistry for detection of falsified drugs

The twelve lanes contain all the reagents needed to carry out tests for different chemicals and functional groups. For example, one lane contains copper(II) and a base; these materials give a characteristic forest-green color with any beta-lactam type antibiotic. That copper lane gives a different, and distinctive, color with metformin, which is a diabetes medication.  Another lane contains a series of reagents that generate a reactive species that can detect phenol groups, found in drugs like acetaminophen or amoxicillin. Other lanes specialize in detecting inert fillers like maize meal, or substitute drugs like acetaminophen that might be added to replace a more expensive medication.  We're always looking for more chemistry to expand the types of drugs we can detect.

The contents of a pharmaceutical generate a color bar code

The 12 lanes produce unique chemical fingerprints for many pharmaceuticals.  Some lanes can give more than one color, or can produce colors in different locations within the lane, depending on the ingredients present in the pill. The colors look a bit like a bar code.  Since computers are good at reading bar codes, we are developing computer software to read the test outputs automatically.

How well do the tests work?

To date, we have recorded unique color bar codes for more than 60 different pharmaceuticals with our current 12-lane PAD.  In some cases, the PAD can identify substandard pharmaceuticals based on differences in chemical composition. Shown below is an example of test outcomes for falsified (left) and authentic (right) Coartem. The fake contains an unexpected ingredient, which is not present in genuine Coartem. 


Fabrication of the test cards

The paper test cards contain a library of chemical color reactions, each isolated in its own reaction lane by hydrophobic barriers that are printed onto the paper using Whitesides-type wax printing. We start with Ahlstrom 319 chromatography paper, which is a heavy paper made of pure cellulose fibers. We use a color laser printer to print the QR code, color standards, and lane labels, then a Xerox ColorQube wax printer is used to print the lines that will separate the lanes. After a quick bake to make the wax soak into the paper, the test cards are cut out. We use a Biomek spotting robot to place spots of different reagents into the lanes, inspect to make sure everything looks correct, and then stamp the test cards with a serial number. We have made over 15,000 test cards.

Research bibliography  (email to request a pdf of any publication behind a pay wall)

Other publications (conference)

  •  "Lab-on-paper developed to monitor iodized salt," N. Myers, M. Lieberman,  ICCIDD newsletter May 2014

  • "Paper analytical devices for detection of low-quality pharmaceuticals," A. Weaver* and M. Lieberman,  Proceedings of the SPIE - The International Society for Optical Engineering, 2014, Vol. 8976 89760H-1

  • "Catching the counterfeits," E. Bajema, T. Barstis, and M. Lieberman, Chemistry & Industry, 77: 28–30.  2013 doi: 10.1002/cind.7701_6.x

  • “Bounded Crowd Sourcing: A twist on open crowd sourcing offers promise for global health efforts,” M. Lieberman, E. Michael, and J. Bock, Monday Developments (a monthly magazine of in-depth news and commentary on global trends that affect relief, refugee, and development work as a service to U.S. humanitarian organizations), July 2011, 29(9), 27-28.