Photographs by Ken Richardson Diagnostics for All, a nonprofit
in Cambridge, Massachusetts, is making a test for liver damage
that could cost just pennies. It consists, remarkably, of a
stamp-size square of paper with wells that change color when a
drop of blood is applied. The test could provide an enormous
benefit in poor countries, where liver damage is widespread as a
side effect of drugs administered to HIV and tuberculosis
patients. (As many as one-fourth of people taking antiretroviral
drugs in the poor world develop liver problems—five times the
rate elsewhere.) The liver function tests administered regularly
in the developed world require tubes of blood, lab equipment,
and electricity. The paper chip from Diagnostics for All needs
none of that. The test uses patterned channels and wells to
allow for filtering and multistep reactions; the technology
originated in the lab of Harvard chemist George Whitesides, who
pioneered this method, and was licensed from Harvard (see “Paper
Diagnostics”). The paper