Biomedical Engineering Reference
In-Depth Information
SU-8:
A negative photoresist (chemically speaking, a photosensitive epoxy which, when exposed,
becomes a hard polyester), developed by IBM in the late 1990s, that can be patterned
with high aspect ratios and develops with high selectivity, hence it has become the pre-
ferred photoresist of choice for microluidics applications.
succinimidyl ester:
Amine-reactive group commonly used in heterobifunctional cross-linkers;
usually seen abbreviated as “NHS ester” in the literature.
surface acoustic wave:
In MEMS, surface acoustic wave (SAW) devices are devices that contain
interdigitated transducers that convert electrical signals into acoustic waves by means
of piezoelectric materials.
surface-bound immunoassay:
See
heterogeneous-phase immunoassay.
surface energy:
he excess energy at the surface of a material compared with the bulk; equiva-
lently, a measure of the loss in total molecular cohesive energy (from the breaking of
bonds) that occurs when a surface is created. It is measured in Joules per square meter.
surface engineering:
Subdiscipline of materials science that involves manipulating and design-
ing the properties and the structure of the surface of materials to obtain better materials.
surface micromachining:
Micromachining of a wafer by additive or subtractive processes that
afect only its surface layer;
see
micromachining.
surface tension:
A property of the surface of a liquid (i.e., a liquid-liquid, a liquid-gas, or a
liquid-solid interface) that allows it to resist external forces on a millimeter or sub-
millimeter scale. It is measured in units of force per unit length (e.g., N/m, dyne/cm).
he generalization of this concept to both liquids and solids and all length scales is
termed surface energy (
see
surface energy). Surface tension governs the formation of
bubbles, droplets and puddles and explains why certain water bugs are able to stride
on water. Surface tension has been exploited in microluidics to build micropumps and
microvalves.
surface tension-driven micropump:
Micropump design that takes advantage of surface tension
efects to propel the luid forward.
syringe pump:
A type of laboratory and clinical-use pump that consists of a syringe the plunger
of which is driven with an electrical (usually programmable) motor.
T
T- or Y-mixer:
A two-inlet, one-outlet microluidic mixer of planar architecture. he inlets
are usually designed to converge in a symmetrical “T” or “Y” coniguration, hence its
name. It is arguably the simplest microluidic design for mixing luids on a microscale
that can be conceived; it relies solely on difusion across the lat interface between the
two luids to achieve mixing; therefore, it is also a highly ineicient design.
Taylor dispersion:
Smearing of the concentration distribution (of a given solute) in a low pipe
or duct by efect of a nonuniform velocity low proile. It was irst described by Sir G. I.
Taylor.
Tesla mixer:
A type of microluidic mixer that incorporates a Tesla valve to induce the forma-
tion of vortices, which enhance mixing;
see
Tesla valve.
Tesla valve:
A valve that preferentially allows low in one direction without moving parts. Tesla
valves do not close in the reverse-low coniguration; they simply display a higher low
resistance.
thermoplastic polymer:
A polymer that can be molded into shapes above its glass transition
temperature.
thermoset polymer:
A polymer that cures irreversibly into a hard matrix, either through heat, a
chemical reaction, or irradiation.
tubeless microluidics:
A class of microluidic devices that does not require tubing for the intro-
duction of luids into the inlets; in these devices, the inlets are an integral part of the
