am6b06305_si_001.pdf (2.34 MB)
Elastomeric PDMS Planoconvex Lenses Fabricated by a Confined Sessile Drop Technique
journal contribution
posted on 2016-07-15, 00:00 authored by S. Ekgasit, N. Kaewmanee, P. Jangtawee, C. Thammacharoen, M. DonphoongpriThe
ubiquity of high quality smartphones at affordable prices not
only accelerated the social penetration in the global population but
also promoted nontraditional usage of smartphones as point-of-care
medical diagnostic devices, sensors, and portable digital microscopes.
This paper reveals a simple, rapid, cost-effective, and template-free
technique for mass-scale production of an elastomeric PDMS (ePDMS)
planoconvex lens capable of converting a smartphone into a portable
digital microscope. By taking advantage of the resistance to spreading
of liquid by a sharp edge, highly stable spherical cap of viscous
liquid PDMS (lPDMS) on a smooth PMMA circular disk was fabricated.
The axisymmetric spreading of lPDMS under the gravitational force
and interfacial tension force enable the formation of spherical cap
with a certain radius of curvature. A thermal treatment at 80 °C
for 30 min cured the spherical cap lPDMS into a bubble-free ePDMS
planoconvex lens. Lenses with focal lengths of 55.2–3.4 mm
could be reproducibly fabricated by adjusting the volume of dispensed
lPDMSs and diameter of PMMA disks. High-resolution panoramic microscope
images without a distortion of small cylindrical object could be constructed
on-the-fly using the imbedded smartphone app. Applications of the
smartphone digital microscope equipped with an ePDMS planoconvex lens
for imaging of micro printings, gun shot residues, cylindrical objects,
and bullet toolmarks were explored.