suitable for applications such as smart glasses, hearing aids
and fitness bands; its nominal capacity of 13 mAh and
3.75 V output allows for Bluetooth and NFC (near-field
communication) links with smartphones.
The future holds out promise for batteries orders of
magnitude smaller: a team at Harvard has demonstrated
a 960µm x 800µm battery using 3-D printing, and
researchers at the University of Maryland have
constructed a battery out of millions of “nanobatteries”,
each 50 µm tall and 250 nm wide, connected in parallel to
form an array. Each nanobattery contains
an anode, a cathode and a liquid electrolyte
and is confined within the nanopores of an
anodic aluminum oxide structure.
Miniature Motors
In the operating room, surgical
procedures such as laproscopy and
endoscopy require highly compact
microdrives for positioners and other
actuators; the drives must also be
bioinert and withstand a range of
sterilization procedures including
autoclave, sterrad, EtO, gamma, and
chemical sterilization.
Stepper motors are popular for these
applications due a combination of high
performance and small size; for example,
Faulhaber offers products with diameters
down to 6 mm and lengths of 9. 5 mm.
Other manufacturers have introduced
miniature stepper motors aimed at the
portables market. Japanese manufacturer
Nidec-Sanyko, for example, has a
miniature 2-phase stepper motor with a
4-wire interface that features a diameter
of 10mm and a height of 12 mm;
operating from 5VDC, the unit comes
with a gear of 3. 5 mm diameter.
In addition to the medical applications
mentioned above, miniature brushless
DC (BLDC) motors are used in
micro-robotics, SLR cameras and
semiconductor manufacturing. Namiki
offers a 10 mm-long BLDC with a
diameter of 2. 4 mm which has a no-load
speed of 650 rpm and a stall torque of
200 µNm; 1.5 mm diameter models are
in the prototype stage.
Miniature RFID Tags
Miniature components lead to miniature
products, which in turn spawn innovative
new applications; trying to understand and prevent
bee colony death, scientist and engineers at CSIRO,
Australia’s national science agency, have developed a
monitoring system that uses RFID tags small enough to
be attached to individual honey bees.
The system relies on the IM5-PK2525 Ultra Small
Package Tag (USPT) from Hitachi Chemical, which
incorporates the Monza 5 tag chip from Seattle-based
Impinj. The UHF tag has a carrier frequency of 860 –
920 MHz; it transmits a 96-bit Transponder ID (TID)
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