We report a simple means to build
a model atomic force microscope
(AFM) using 3D printing of thermoplastic materials that are commercially
available. The model has many of the key parts of an actual AFM including
a z-axis stage, an AFM head with a cantilever assembly,
and a laser source that reflects off of the back of the cantilever.
Using a magnet attached to the tip of the cantilever and a metal sample,
this model AFM enables acquisition of force–distance profiles
with characteristic snap-in, pull-off, separate, and contact regions.
The model AFM was designed, printed, and used by first- and second-year
undergraduate students. Through completion of this project, students
learned scientific instrument design and construction via 3D printing
and obtained first-hand practice in the measurement of force–distance
profiles and the elastic constants of cantilevers. The open design
of the model can easily accommodate additional capabilities in which
students are interested, e.g., topographical scanning and using cantilevers
made from different materials.
High pressure assisted infusion of nutrients into food was in situ monitored with magnetic resonance imaging (MRI). Modification of an off-the-shelf pressure reactor with an MRI detection circuit provided a large enough volume to accommodate food. The model food used here was peeled apple flesh as it is considered as a good mimic for fibrous food. The nuclear spin relaxation properties of the water surrounding the apple flesh were enhanced by adding paramagnetic manganese cations. In this way, MRI relaxation contrast can be used to monitor the location of doped bulk water in and around the apple flesh during pressurization. This work tracked the efficiency of pressure induced nutrient infusion in situ, demonstrating that pressure gating and ramping offer no nutrient mass transport advantage over operation at constant pressure and that the presence of a peel expectedly disrupts solute transport into the fruit. High pressure assisted infusion, with all pressurization strategies shown here, yielded nearly 100-fold faster infusion times than at ambient pressure.
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