Supplementary Materials for

Bioinspired photocontrollable microstructured transport device

Emre Kizilkan,* Jan Strueben, Anne Staubitz,* Stanislav N. Gorb*

*Corresponding author. Email: ekizilkan@zoologie.uni-kiel.de (E.K.); staubitz@uni-bremen.de (A.S.);

sgorb@zoologie.uni-kiel.de (S.N.G.)

Published 18 January 2017, Sci. Robot. 2, eaak9454 (2017)

DOI: 10.1126/scirobotics.aak9454

The PDF file includes:

Legends for movies S1 to S5

Fig. S1. Fabrication steps for obtaining the BIPMTD.

Fig. S2. Custom-made setup for adhesion measurement of the BIPMTD under UV

light illumination.

Fig. S3. The model for calculation of the angle of curvatures after UV

illumination on the BIPMTD.

Fig. S4. Observation of temperature change of BIPMTD and PDMS samples

during UV light illuminations.

Fig. S5. Continuous UV light illumination of the BIPMTD in contact to a force

sensor.

Other Supplementary Material for this manuscript includes the following:

(available at robotics.sciencemag.org/cgi/content/full/2/2/eaak9454/DC1)

Movie S1 (.mp4 format). The volume change of the BIPMTD under UV light

illumination.

Movie S2 (.mp4 format). The observation of the BIPMTD illuminated for 30 s

through different UV filters with transmissions of 25, 50, 90, and 100% (no

filter).

Movie S3 (.mp4 format). Transportation of a glass sphere (Ø = 1mm) through UV

light–driven volume change of the BIPMTD.

Movie S4 (.mp4 format). Demonstration of the BIPMTD as a pick-and-drop

material for a circular glass slide with a diameter of 15 mm and a thickness of

0.12 mm.

robotics.sciencemag.org/cgi/content/full/2/2/eaak9454/DC1

Movie S5 (.mp4 format). Demonstration of the BIPMTD as a pick-and-drop

material for an empty Eppendorf tube (XC63.1, Carl Roth GmbH + Co. KG) with

a volume of 1.5 ml.

Supplementary movie descriptions

Movie S1. The volume change of the BIPMTD under UV light illumination. The

BIPMTD recovers its shape when the UV light illumination ceases.

Movie S2. The observation of the BIPMTD illuminated for 30 s through different UV

filters with transmissions of 25, 50, 90, and 100% (no filter).

Movie S3. Transportation of a glass sphere (Ø = 1mm) through UV light–driven volume

change of the BIPMTD. The sphere is picked up from a flat PDMS surface and transported

laterally by a driven micromanipulator on a Mushroom-Shaped Adhesive Microstructure

(MSAMS) surface. The volume change creates a contact between MSAMS surface and the

sphere that was picked up. The cessation of UV light illumination induces sphere detachment

from the MSAMS surface.

Movie S4. Demonstration of the BIPMTD as a pick-and-drop material for a circular

glass slide with a diameter of 15 mm and a thickness of 0.12 mm.

Movie S5. Demonstration of the BIPMTD as a pick-and-drop material for an empty

Eppendorf tube (XC63.1, Carl Roth GmbH + Co. KG) with a volume of 1.5 ml.

Production of the BIPMTD

In order to produce the MSAMS pillars, a negative epoxy resin template was prepared from

the commercially available sample of Gecko®-Tape (Gottlieb Binder GmbH, Holzgerlingen,

Germany) congruent to two-step molding method (Fig. S1) (27, 28). The MSAMS was made

of polydimethylsiloxane (PDMS) form which had 10:1 base to curing agent ratio (Sylgard 184,

Dow Corning). The liquid PDMS precursors were applied to the MSAMS template and

degassed for 30 min in a vacuum chamber at 1 mbar. After degassing, the porous LCE

produced according to previous work (18), was placed onto the template and pressed with a

homemade hand-roller a onto PDMS for the compliance of the film. Then, a further degassing

step of 30 min in a vacuum chamber at a pressure of 1 mbar followed. Subsequently, the

PDMS was applied onto the LCE film to seal the backing layer. Finally, the structure was

cured at 70°C for 2h.

Fig. S1. Fabrication steps for obtaining the BIPMTD.

Set-Up for Force Measurements

For the force measurements, a custom-made system was used that consists of a force

transducer (10 g capacity, Biopac Systems Ltd, Santa Barbara, CA, USA) combined with a

motorized micromanipulator DC3314R (World Precision Instruments, Inc., Sarasota, FL) and

a controller MS314 (World Precision Instruments Inc., Sarasota, FL, USA). A 1 mm Ø

sapphire glass sphere was mounted to the sensor for the force measurements (Fig. S2.). The

glass sphere was brought into contact with the surface and detached from it with the velocity

of 200 µm s−1. Force–time curves were recorded using the software AcqKnowledge 3.7.0

(Biopac Systems, Inc., Goleta, CA, USA). The glass sphere was brought to the surface, on

which the pull off force was measured. The light source was located at the opposite side of the

glass sphere. For the transmission experiment, three different short-pass filters were used

which allowed the transmission of UV light (25% transmission: XB07, Horiba Scientific, UK;

50% transmission: 03FCG001, Melles Griot, The Netherlands; 90% transmission: 03SWP402,

Melles Griot, The Netherlands).

Fig. S2. Custom-made setup for adhesion measurement of the BIPMTD under UV light

illumination.

Deformation Strain Calculations

The length change of BIPMTD sample during UV light illuminations in Fig 2. C and Movie

S2. were measured by software ImageJ 1.47v (NIH, USA). The length values calculated were

used to obtain engineering strain by equation (1)

𝜀 = l1−l0

l0=

r+g−r (dθ)

r (dθ) (1)

where ε = strain, l0 = initial length, l1 = length after UV light illumination, r = radius of

curvature, g = geometrical deformation and dθ = differential the angle of curvature. The angle

of curvature values were calculated by the model in Fig S3. and equation (1).

Fig. S3. The model for calculation of the angle of curvatures after UV illumination on

the BIPMTD.

Thermal imaging camera observations

In order to quantify the thermal influence of UV light, the BIMTD and PDMS sample with

same size were observed by a thermal imaging camera (Trotec IC 080V, Heisenberg,

Germany).The BIPMTD and PDMS sample were subjected to the 30s of UV light

illumination. The temperatures at 5 s and 30 s UV source-on and 10 s and 30 s after UV

source-off were recorded (Figure S4). The thermal imaging camera observations showed that

UV absorption of azobenzene units in LCE induced a temperature increase up to 39.37ºC

within 5s and 48.8 ºC within 30s of illumination at the center of the BIPMTD (Fig S4 C-ii,

iii). The temperature of the glass slide-BIPMTD interface was 29.5 ºC at 5s and 33.8 ºC at 30 s

of UV light illumination (Fig S4 C-ii, iii). Following the turning-off of the UV light source,

the temperature decreased 29.9 ºC in 10 s and to room temperature in 30 s (Fig S4 C-iv, v).

A PDMS sample at same dimensions of BIPMTD was used in the Fig. S4 D-F. It was

observed under UV light illumination with the thermal imaging camera for 30 s. The

temperature difference of PDMS sample were 0.14 ºC in 5s and 0.8 ºC in 30s of UV light

illumination. This influence of the UV light on PDMS sample is very small to be neglected

and can be due to the small UV absorption of PDMS and/or due to temperature increase in the

UV light source.

Fig. S4. Thermal imaging camera observations of BIPMTD (A-C) and PDMS (D-F) under

UV light illumination. Each sample of BIPMTD (C-i-v) and PDMS (F-i-v) was observed for

30s under UV light illumination and for 30 s after UV light source was turned off. The cone in

the images is from the light source and the indicated square shows the polymer film from top.

Continuous illumination of BIPMTD

The BIPMTD was brought to contact (by normal preload-similar to Fig. 2) as in Fig S2 and

exposed to UV light illumination for 9 min. The light triggered force increased dramatically at

0-30 s (slope=-6.35) and relatively slower at 30 s-9 min (slope=-0.1).

Fig. S5. Continuous UV light illumination of the BIPMTD in contact to a force sensor.

The light-induced force was more at 0-30 s than 30s-9min.

Relative thickness comparison of layers of the BIPMTD

To answer the question of importance of the relative thicknesses, the work done through light

illumination has been calculated for different ratio of thicknesses of PDMS and LCE layers.

The work done was addressed as elastic strain energy, U and calculated by using equation (2)

and (3).

𝑈 = 𝑃2𝐿

2𝐸BIPMTD𝐴 (2)

𝐸BIPMTD = (𝐸PDMS

x 𝑉PDMS)+ (𝐸LCE x 𝑉LCE)

(𝑉PDMS+ 𝑉LCE) (3)

where P = light-induced force, L = length of the sample, E = Elastic modulus, A = cross

sectional area and V = volume.

With keeping the LCE layer thickness fixed (“1”=100 µm), the thickness of the PDMS layers

were varied. We have taken into account three different ratios for the design of PDMS (top):

LCE (middle):PDMS (bottom); 1:1:1 (our design), 0.5:1:0.5 and 2:1:2. The thickness ratios of

PDMS-LCE-PDMS and respective elastic strain values were calculated as:

1) 1:1:1 (our design); U = 3.175*10-9 J,

2) 0.5:1:0.5; U = 6.06*10-9 J,

3) 2:1:2; U = 1.625*10-9 J.

This results show that if the relative thicknesses of PDMS layers are bigger than LCE layer

(2:1:2), the deformation through light-triggered force is smaller.