Optical tweezers can be used to sculpt microscopic oil or monomer droplets by lowering their surface tension with surfactants. Multiple laser traps can deform a single droplet into various 3D shapes and connect multiple droplets with nano-scale threads. This technique could potentially solidify shapes through polymerization and create nanofluidic networks for chemical synthesis.

1. Optical Sculpting
Inventors:
Dr. Andy Ward
Prof. Colin Bain
Sponsored by:

2. Introduction
Optical tweezers use the forces
exerted by a tightly focussed laser
beams to capture and manipulates
microscopic particles such as
polymer beads and bacteria
We’ve found by placing an oil droplet in an aqueous solution and
adding just the right surfactants, you can lower the surface tension
just enough that the weak laser forces can deform the droplet.

3. Key Features
• Capture micron sized oil or monomer droplet
• Create micro sized 3D shapes by moving laser traps in
multiple positions.
• Potentially solidify the shape by polymerisation if it’s
comprised of a monomer (~ 1 drop/sec)
• Can create a 3D network of multiple droplets connected by
very fine (<100nm) threads -> nanofludic networks for
chemical synthesis

4. Shape formation
• Droplets are deformed by traps pulling at each corner
• Laser power is 24 mW shared between the trapping
positions
Final deformations for 1, 2, 3
and 4 trap arrangements.
Scale bar 2 microns

5. Thread formation
At very low interfacial tensions and higher laser
powers
• Single droplet is separated into two droplets which are
connected by thin threads (barely visible < 100 nm)
• Droplets can readily re-coalesce
• Threads are stable
a) b) c)
d) e) f)

6. Nanofluidic Networks
• Single droplet is separated into
three droplets which are
connected to the centre drop by
thin threads. Drop in centre is
not trapped
• Small droplets on the outside
grow with time.
• Large droplet in the centre
shrinks
• Eventually a y-junction is formed
with the threads

7. Thanks to:
• STFC funding of facility access beam-time for Prof Colin
Bain
• EPSRC current funding (EP/I013377/ 1)
And of course our challenge sponsors!