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101Fraunhofer Institute for Laser Technology ILT, www.ilt.fraunhofer.de

DQS certified by DIN EN ISO 9001, Reg.-No.: DE-69572-01

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4U-shapedmicrofilaments.

5 Illuminated, radially symmetrical

microfilamentarrays.

Result

Arrays of filaments of different geometries and lengths were

produced using the method described. Two examples are illus-

trated above. Fig. 5 shows radially symmetrical microfilament

arrays in which the individual filaments have a diameter of

100 μm and a length of 1 mm. Fig. 4 shows filaments with

a U-shaped cross-section. The different geometries result in

microfilaments with different bending and breaking strengths.

applications

Synthetic microfilaments can be used in combination with

suitable piezoelectric devices as tactile sensors. Radially

symmetrical microfilament arrays, for instance, can be used

in medical devices to detect and diagnose stenosis and arterial

insufficiency. Another area of application for microfilaments

is flow testing, where flow characteristics can be established

by measuring the deflection of the filaments.

contacts

Dipl.-Phys. Moritz Schaefer

Phone +49 241 8906-305

moritz.schaefer@ilt.fraunhofer.de

Dr. Arnold Gillner

Phone +49 241 8906-148

arnold.gillner@ilt.fraunhofer.de

task

Microfilaments are commonly found in nature. Many animals

use them as sensors to obtain information on their environ-

ment. Grasshoppers, for example, have microscopic hairs on

their backs measuring up to 1 mm in length, which they use

to sense the direction of low-frequency noises. In order to

develop technical applications that mimic this highly efficient

sensor concept, there is a need for a method of fabricating

microfilaments with a diameter of between 20 and 100 μm

and a length of up to 1 mm.

Method

The microfilaments are cast in polycarbonate molds in which

microscopic holes have been drilled using an excimer laser.

The use of a mask-projection laser ablation technique enables

a wide variety of hole geometries, and hence filament geo-

metries, to be produced by selecting appropriate mask layouts.

To fabricate the microfilaments, polydimethylsiloxane (PDMS,

a silicone compound) is poured into the mold, hardened,

and peeled off. Since the mold is not destroyed by this

process, it can be reused.

synTheTIc MIcro fILaMenTs for use as sensors

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