The Chemically-Active Toy (CAT): Soft Robotics at BYU-Idaho Jonathan K. Meyers, Andrew T. Sevy, Hector A. Becerril

Brigham Young University - Idaho

Results Introduction Discussion

Acknowledgements

Methods

The emerging field of soft robotics has potential applications in

medical, military, and personal domains.[1,2] While traditional

“hard” robots are effective in many industrial and

manufacturing processes, their use is limited by safety

concerns and environmental requirements (e.g. temperature,

terrain, tethering, etc.). Soft robots have the potential to

extend beyond those limitations as they are made of flexible

materials designed to perform in a multitude of environments

and be more compatible with biological organisms.[3]

Small soft robots have been created in various forms[1] (e.g.

hand, arthropod,[3] tentacles,[4] and fish[5,6]). Actuation can be

powered by air compressed by various means,[3,6] one being a

catalyzed decomposition of hydrogen peroxide, called the

pneumatic battery.[7,8]

Figure 4: Pressure buildup and release in the pneumatic battery.

“Effective” (red) and “ineffective” (blue) cycles were defined by slope.

References

The authors would like to thank:

• Richard Grimmett (BYU-I) for the use of his 3D printer

• Ben Finio (Instructables); for the design of the gripper mold

• BYU-I Physics Department for the electronic supplies

• BYU-I Chemistry Department for the support and materials

The creation of the gripping robot required the development of

a unique blend of polymers to provide optimal flexibility and

strength; without this blend, the robot components do not bond

together. These grippers successfully grasp and lift objects,

but their lifespan tends to be short – perhaps a dozen cycles.

Future research will investigate composite materials to reduce

fatigue and overstretching and improve manufacturing

techniques. Additionally, more-advanced soft robots will be

constructed using the techniques developed in this work.

The source of pressure in the pneumatic battery is the silver-

catalyzed decomposition of hydrogen peroxide:

2𝐻2𝑂2(𝑙) → 2𝐻2𝑂(𝑙) + 𝑂2(𝑔)

The battery presented here is more economical than other

versions previously reported.[7,8] To prevent damage to the

battery, maximum pressure was kept under 30 kPa therefore

we can’t compare our max. pressure with the literature.

Importantly, our rate of pressure buildup was over 50% faster.

Improving the shut-off mechanism will increase the maximum

pressure as well as the recharge rate. With a more responsive

mechanism, better catalysts and fuels could be explored for

actuating larger soft robots. These changes may lead toward

more mobile and powerful pneumatic batteries.

Figure 1: Mold being printed (left) on a Solidoodle 3D printer (right)

• Gripper robot mold printed by 3D printer (Figure 1)

• Silicone rubber (Ecoflex 00-30) cast in mold to create body

• 20% PDMS (Sylgard) in Ecoflex used to cast palm-side

• Gripper fused together and tethered to pressure source

Figure 3: demonstration of

gripper actuation (left) and

lifting (above)

• Ten gripping robots were produced with varying techniques

• Gripper actuation requires approximately 27 kPa

• Gripper can lift at least 40 g

• Challenges:

• Arms tend to actuate unevenly

• Materials fatigue over time

• Pressure escapes from tethering system

• Ecoflex and PDMS do not bond well together

• Pneumatic battery was constructed from repurposed water

bottle (see Figure 2)

• Silver foil was attached in the reaction well (under cap)

• Parts were constructed from Ecoflex and PDMS

• Cap was modified to fit a tubing adapter

Figure 2: Schematic of pneumatic battery (left) including silver

catalyst (red lines); actual pneumatic battery (right)

T H E G R I P P E R

T H E P N E U M AT I C B AT T E R Y

co

urt

esy o

f so

lido

od

le.c

om

During nine effective cycles (first 40 min):

• 227.65 kPa produced (6.80 kPa/min average)

• 45.14% of possible O2 was produced from H2O2

• 3.97 min to build enough pressure for gripper

• 15.11 gripper actuations per hour

• 10 mL H2O2 per gripper actuation

[1] Kim, S.; Laschi, C.; Trimmer, B. Trends in Biotechnology. 2013, 31, 287-294.

[2] Majidi, C. Soft Robotics. 2014, 1, 5-11.

[3] Shepherd, R.F.; Ilievski, F.; Choi, W.; Morin, S.A.; Stokes, A.A.; Mazzeo, A.D.;

Chen, X.; Wang, M.; Whitesides, G.M. PNAS. 2011, 108, 20400-20403.

[4] Laschi, C.; Mazzolai, B.; Mattoli, V.; Cianchetti, M.; Dario, P. Bioinsp. Biomim.

2009, 4, 1-8.

[5] Marchese, A.D.; Onal, C.D.; Rus, D. Exp Rob. 2013, 88, 41-54.

[6] Marchese, A.D.; Onal, C.D.; Rus, D. Soft Robotics. 2014, 1, 75-87.

[7] Onal, C.D.; Chen, X.; Whitesides, G.M.; Rus, D. In: International Symposium on

Robotics Research (ISRR). 2011.

[8] Turchetti, L.; Vitale, F.; Accoto, D.; Annesini, M.C. Ind. Eng. Chem. Res. 2013, 52,

8946-8952.