MEMS/NEMS and BioMEMS/BioNEMS Materials and Devices and Biomimetics Prof. Bharat Bhushan Ohio Eminent Scholar and Howard D. Winbigler Professor and Direc tor NLBB [email protected] Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics © B. Bhushan Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Micro/nanoscale studies Materials/Device Studies Bio/nanotribology Bio/nanomechanics Biomimetics • Materials/coatings Materials sci ., biomedical eng ., physics & physical chem . • SAM/PFPE/Ionic liquids • Biomolecular films • CNTs Techniques • Micro/nanofabrication AFM/STM Microtriboapparatus Nanoindentor Numerical modeling and simulation Collaborations Applications • MEMS/NEMS • BioMEMS/NEMS • Superhydrophobic surfaces • Reversible adhesion • Beauty care products • Probe-based data storage • Aging Mech. of Li-Ion Batt. Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics 3 Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Outline • Background Definition of MEMS/NEMS and characteristic dimensions Examples of MEMS/NEMS and BioMEMS/bioNEMS with nanotribology and nanomechanics issues Biomimetics – Lessons from Nature • Experimental Atomic force/Friction force microscope (AFM/FFM) • Tribological Studies of Si and Related Materials Virgin, treated/coated silicon; polysilicon films and SiC film • Tribological Studies of Lubricants Perfluoropolyether lubricants and self-assembled monolayers • Bioadhesion Studies Surface modification approaches to imp rove bioadhesion • Device Level Studies Adhesion, friction and wear measurements using a microtriboapparatus Nanotribological characterization of digital micromirror devices (DMD) • Hierarchical Nanostructures for Superhydrophobicity, self cleaning and low adhesion (Lotus Effect) Roughness optimization for superhydrophobic and self cleaning surfaces Experimental studies • Hierarchical Nanostructures for Reversible Adhesion (Gecko Feet) Hierarchical structure for adhesion enhancement Roughness optimization for reversible dry adhesives (not included) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Background Definition of MEMS/NEMS and characteristic dimensions MEMS - characteristic length less than 1 mm, larger than 100 nm NEMS - less than 100 nm Human hair 50-100 μm DMD 12 μm 500 nm Quantum-dots transistor 300 nm Red blood cell 8 μm Molecular gear 10 nm-100 nm SWNT chemical sensor 2 nm C atom DNA 0.16 nm 2.5 nm 0.1 1 10 100 1000 10000 100000 Size (nm) Characteristic dimensions in perspective B. Bhushan, Springer Handbook of Nanotechnology, Springer, 2nd ed. (2007) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Stiction – High static friction force required to initiate sliding. Primary source is liquid mediated adhesion Formation of meniscus and contribution to the attractive force B. Bhushan, Introduction to Tribology, Wiley, 2002 Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Examples of MEMS/NEMS and BioMEMS/NEMS springs shuttle Microgear unit can be driven at speeds up to 250,000 RPM. Various sliding comp. are shown after wear test for 600k cycles at 1.8% RH (Tanner et al., 2000) gears and pin joint Microengine driven by electrostatically-actuated comb drive Stuck comb drive Sandia Summit Technologies (www.mems.sandia.gov) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Microfabricated commercial MEMS components 8 Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics The generating points of friction and wear due to interaction of a biomolecular layer on a synthetic microdevice with tissue (Bhushan, Lee et al., 2006) 9 Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Need to address nanotribology and nanomechanics issues • The nanotribology and nanomechanics problems can drastically compromise device performance and reliability. To solve these problems, there is a need to develop a fundamental understanding of adhesion, friction/stiction, wear and the role of surface contamination and environment in MEMS/NEMS and BioMEMS/NEMS. This can be done by studying Nanotribology and nanomechanics of MEMS/NEMS materials Lubricant methods for MEMS/NEMS Bioadhesion Studies Development of superhydrophobic surfaces Device level studies Approach • Use an AFM/FFM for imaging and to study adhesion , friction, scratch and wear properties of materials and lubricants, which better simulates MEMS/NEMS and BioMEMS/BioNEMS contacts • Develop and employ techniques to measure tribological phenomena in devices B. Bhushan et al., Nature 374, 607 (1995); B. Bhushan, Handbook of Micro/Nanotribology, second ed., CRC Press, 1999; B. Bhushan, Introduction to Tribology, Wiley, NY, 2002; B. Bhushan, Springer Handbook of Nanotechnology, 2nd ed., 2007; B. Bhushan, Nanotribology and Nanomechanics – An Introduction, Springer, 2005. Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Lessons From Nature (Biomimetics) Biomimetics • Nature has gone through evolution over 3.8 billion years. It has evolved objects with high performance using commonly found materials. • Biomimetics means mimicking biology or natu re. It is deriv ed from a Greek word “biomimesis.” Other words used include bionics, biomimicry and biognosis. • Biomimetics involves taking ideas from nature and implementing them in an application. • Biological materials have hierarchical structure, made of commonly found materials. • It is estimated that the 100 largest biomimetic products had generated $1.5 billion over 2005-08. The annual sales are expected to continue to increase dramatically. M. Nosonovsky and B. Bhushan (2008), Multiscale Dissipative Mechanisms and Hierarchical Surfaces: Friction, Superhydrophobicity, and Biomimetics, Springer-Verlag, Heidelberg, Germany; B. Bhushan (2007), Springer Handbook of Nanotechnology, second ed., 11 Springer-Verlag, Heidelberg, Germany; B. Bhushan, Phil. Trans. R. Soc. A 367, 1445-1486 (2009). Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Overview Overview of various objects from nature and their selected ftifunction 12 B. Bhushan, Phil. Trans. R. Soc. A 367, 1445-1486 (2009). Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Montage of some examples from nature. 13 B. Bhushan, Phil. Trans. R. Soc. A 367, 1445-1486 (2009).). Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Experimental Atomic force/Friction force microscopp(e (AFM/FFM) • At most interfaces of technological relevance, contact occurs at numerous asperities. It is of importance to investigate a single asperity contact in the fundamental tribological studies. Engineering Interface Tip - based microscope allows simulation of a single asperity contact • Nanotribological studies are needed To develop fundamental understanding of interfacial phenomena on a small scale To study interfacial phenomena in micro- or nanostructures and performance of ultra-thin films used in MEMS/NEMS components Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Large sample AFM/FFM Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Square pyramidal Square pyramidal Three-sided pyramidal silicon nitride tip Single-crystal silicon tip (natural) diamond tip Carbon nanotube tip Various AFM tips Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Tribological Studies of Si and Related Materials Macroscale friction and wear performance of silicon and effect of ion implantation Reciprocating sliding tests against an alumina ball at 1 N load. V refers to virgin silicon. S and P correspond to doped single-crystal and polycrystalline silicon. Ion energy used was 200 keV. B. K. Gupta, B. Bhushan et al., ASME J. Tribol. 115, 392 (1993); B. K. Gupta, B. Bhushan et al., Tribol. Trans. 37, 601 (1994) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Scratch, wear and nanoindentation of virgin and treated/coated silicon Microscale scratch tests usinggp a diamond tip in an AFM B. Bhushan and V. N. Koinkar, J. Appl. Phys. 75, 5741 (1994) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Friction, scratch, wear and nanoindentation of polysilicon films and SiC film • Polysilicon films, undoped and doped are commonly used as MEMS materials • Silicon-based MEMS devices lack high-temperature capabilities with respect to both mechanical and electrical properties • SiC is being pursued as a material for high-temperature microsensor and microactuator applications based on its successful use in high-power devices Density Hardness Elastic Fracture Thermal Coeff. of Melting Band- Sample (kg/m3) (GPa) modulus toughness conductivity thermal point gap (GPa) (MPa m1/2) (W/m K) expansion (οC) (eV) (x 10-6 / οC) β-SiC 3210 23.5-26.5 440 4.6 85-260 4.5 - 6 2830 2.3 Si(100) 2330 9-10 130 0.95 155 2 – 4.5 1410 1.1 Selected bulk properties of 3C SiC and Si(100) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics AFM 3D maps and average 2D profiles of scratch marks on various samples B. Bhushan, Tribology Issues and Opportunities in MEMS, Kluwer, 1998; S. Sundararajan and B. Bhushan, Wear 217, 251 (1998) Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics Summary of tribological studies of MEMS/NEMS materials • Tribological properties of silicon are inadequate • Ion implantation and oxidation of silicon improve the tribological properties of silicon • SiC exhibits significantly better tribological properties than silicon-based materials and is a good candidate for MEMS/NEMS devices Nanoprobe Laboratory for Bio- & Nanotechnology and Biomimetics