With products perfected over billions of years (of
painstaking evolution), to suit every
tiny creature, in accordance with its unique life style, Nature never
ceases to amaze us. In her ever open house unlimited treasures are flung around with such joyous abandon for us to see,
to feel, to experience and to
learn and above all to mimic. Two
recent research reports reiterate
this undeniable truth further.
Karp etal (1) in their recent
paper discuss a marvelous
biomedical adhesive, inspired by Pomphorhynchus
laevis, indeed too big a name for a tiny parasitic that infects fresh water fish. But
once you realize how cleverly it
uses its head ( both literally and
figuratively ), you will concede the name. Since the parasite has no hands nor feet to cling to its host, it
uses its proboscis, the elongated part
of its head. Proboscis is an interesting word and its genesis is from the Greek word proboscis( προβοσκίς ) which means, somewhat like
move forward to feed. The clever worm inserts its head which as an array of
sharp nanotips into the host’s intestinal wall, the outer cover of the nanotips
then swell, thus ensuring not only a well cushioned anchoring, but also smooth
back tracking, whenever necessary.
Inspired and excited by this
and the umpteen possibilities in soft tissue repair and restoration, Karp's team built a prototype. A simple elastomer sheet with polystyrene spikes each with a sheath of poly( styrene)- poly(acrylic acid)
block copolymer. Acrylic acid is extremely hydrophilic and sticky organic molecule; and poly (acrylic acid) is
even more so. In fact poly (acrylic acid) is the predominant
segment in most of the super absorbent
polymers. So the sheath takes up water,
swells and sticks in place. Now
imagine the immediate possibilities :
first medicating the hydrogel sheath,
next controlling the pore size of the hydrogel for controlled drug delivery, then built-in mechanism for timed hydration and
subsequent dehydration of the sheath so that the spike naturally falls of like
a dry leaf. .
Arthropods (houseflies,
ants, bees etc.) are invertebrates with segmented bodies. This tribe,
has been taunting mankind for long,
with their compound eye. A Compound
eye is made up of a cluster of small simple eyes (singular ommatidium, plural ommatidia). Ommatidia
may lack the fine resolution of the
mammalian eye, but it bestows a panoramic view with unlimited depth of vision low
aberration and above all instantaneous
ability to detect motion, features
extremely desirable in cameras. But then
you need hemispherically configured imaging elements to achieve this. Even
the latest digital cameras work on principles of planar sensors and conventional optics.
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The team demonstrates ”how a
camera can accurately and simultaneously render pictures of multiple objects in a field of view , even
at widely different angular positions and distances.”A cross disciplinary global team has surmounted the difficulties(2) by combining the advantages of stretchable electronics with
hemispherical photodetector arrays. The
prototype digital camera has tiny lenses
molded out of a flexible sheet of poly
(dimethylsiloxane, PDMS for short), connected to a stretchable
mesh of silicon photodiodes and
blocking diodes appropriately placed and connected with whiskers of metal embedded polyimides. Each
Microlens with its own photodetector and
electrical connections is equivalent to
an ommatidium and the manmade ommatidia might roughly look like the bubble
wrap, but several orders of magnitude smaller. A perforated black silicon cap
over the microlens array and a black support below the assembly effectively
cuts off stray light.
1. "A bio-inspired swellable microneedle adhesive for
mechanical interlocking with tissue". Nature Communications 4 (1702). April 2013.
2. Digital
cameras with designs inspired by the
arthropod eye. Song et al Nature , 497,
95-99. 2nd May 2013
