Fabricating low cost and high performance elastomer lenses using hanging droplets

Abstract

Existing methods for low cost lenses using parallel mold stamping and high temperature reflow requires complex engineering controls to produce high quality lenses. These manufacturing techniques rely on expensive equipment. In this paper, we propose a low cost (< $ 0.01 per pc) flexible moldless lens fabrication method based on curing a hanging transparent polydimethylsiloxane (PDMS) elastomer droplet on a curved substrate. Additional deposition of hanging droplets in the same manner led to a substantial increase in the lens curvature and concomitant decrease in the focal length of the PDMS lenses down to ~2 mm. The shortest focal length lenses were shown to collimate light from a bare light emitting diode (LED) and image microscopic structures down to around 4 µm with 160x magnification. Our hanging droplet lens fabrication technique heralds a new paradigm in the manufacture of low cost, high performance optical lenses for the masses. Using these lenses, we were able to transform an ordinary commercial smartphone camera into a low-cost digital dermascope (60x magnification) that can readily visualize microscopic structures on skin such as sweat pores.

Fabricating optical lenses by inkjet printing and heat-assistedin situcuring of polydimethylsiloxane for smartphone microscopy

“…12,14 A recently introduced method of creating PDMS lens by gravity-assisted hanging droplet formation has both the advantage of low cost and good optical quality; however, the process requires iterative drop-bake cycles to achieve the desired focal length. 15 In this paper, we describe a method to fabricate lenses by inkjet printing of PDMS droplets on a heated surface. The small PDMS droplet is released at a prescribed height from the inkjet print head.…”

Low-cost optical manipulation using hanging droplets of PDMS

“…The trapping lens of our optical manipulation system was formed from hanging droplets of PDMS, which had been prepared using the typical so lithography PDMS procedure, and followed similar steps as those outlined by Lee et al, 7 and shown in Fig. 1(a)-(c).…”

“…The particle size was chosen as previous studies 7 have shown the smallest resolvable structure with droplet lenses to be 4 mm. Fig.…”

Bubble wrap for optical trapping and cell culturing

“…The drive to develop technology capable of analysing the outputs from such devices has led to innovations in the area of image processing and analysis on mobile phones [7], along with new low cost, or low-tech, imaging techniques [8][9][10][11] making use of, for example, holographic microscopy. Other areas that have benefited from leveraging consumer technology and simple home-made techniques include miniature dermascopes [12], centrifuges made from egg beaters [13], not to mention the huge potential of 3D printing in such areas, spanning chemical reactionware [14] to conventional printing of chips [15].…”

“…Elastomeric optics have been used in an increasing number of novel applications such as a rubber microscope [18] and biologically inspired wide field lenses [19]. Additionally, lenses based on hanging droplets of PDMS have been fabricated and used in a low-cost digital dermascope [12] and low-cost optical traps [20].…”