Microproducts Chapter 1

Chapter 1

Microproducts

Chapter 1

Microproducts

1.1 Birth and features of microproducts

Microproducts spread out in the eighties in USA with the micro technologies revolution.

Actually, the exploiting of microelectronic-based technologies allowed the batch

fabrication of microelectromechanical devices.

The term “microproduct” refers to all those products with components that have at least

some functional features in the micron range. These microproducts are characterized by

a high integration of many functions of different fields (such as mechanical, electronic,

optical etc.) in a very little volume and their components fulfill several tasks at the same

time (e.g.: an electronic component often has also a structural function). Thus, the

development of microproducts requires interdisciplinary competences but also a product

development that inevitably considers, at the same time, all the aspects of the process

chain (design, material, processing, components, assembly, control and measurement)

[1].

1.2 Typical microproducts and fields of application

Microproducts are very important in every application where small dimension and light

weigh are fundamental (e.g. implantable drug delivery systems) or simply pleasant (e.g.

camera phones). Typical microproducts and main fields they find application are shown in

Table 1 [1][2][3][4][5].

As obvious, some microproducts are strictly associated to a particular field (e.g. IT

components and medical equipments) while others have wide application (e.g.

microactuators, microsensors, micromotors). In addition, some microproducts (e.g.

actuators) can be realized by the exploitation of different working principles that give them

the same function but various designs [1].

Microhandling devices for the assembly of Hybrid Microproducts

Field Microproducts

IT Ink jet printers, reading caps for hard disks, microdisplays,MEMS memories, chip coolers, magnetic bearings.

Medical and Biomedical Heart pace makers, analysis equipment, implantable drug delivery systems, sensors, filters, hearing aids, microtweezers for minimally invasive surgery, micro implant systems, catheters.

Automotive Motion sensors,tire pressure monitors.

Aeronautic & Aerospace Lightweight distributed sensors for micro crack detection. Industry & Automation Micro relays, micromotors, micropumps, microharmonic drives,

accelerometers, gyroscopes, stick slip actuators, magnetic

actuators, piezoelectric elastic force motors, electrostatic actuators. Chemical & Energy Micro fuel cells, lab on chip systems, flow sensors, micro energy

sources, micro-fluidics.

Telecommunication Microphones, RF MEMS, camera phones, MOEMS for Telecom.

Defense MEMS fingerprint, Microdrones.

Optical Optical switches, magneto optical heads, micro-spectrometers, liquid lenses for auto focus/zoom, IR sensors, microlenses, microoptics, optical networks, connectors, micromirrors. Environment monitoring Sensors for chemical analyses of fluids, pressure sensors.

Sport & Entertainment Noise canceller ear plugs, variable stiffness tennis rackets, skis equipped with piezoelectric active dampers.

Watches Gear wheels, microtransmissions, micromotors.

Table 1: Microproducts and their market fields (adapted from [1]).

1.3 Economic aspects of microproducts

Since the eighties, the market of microproducts has grown very fast. In particular, one of

the first deep market analysis carried out in 1996 by NEXUS (the European Network of

Excellence in Multifunctional Microsystems) showed a total world market of microsystems

of 14.4 billion Euros [6]. In 2006, this market had a value of 33 billion and all commercial

analyses predict this market will continue to increase. According to NEXUS previsions,

the global value of microproducts will reach 57 billion Euros in 2009: it means growth

rates of about 15% per year. In Figure 1 it is shown the market analysis and previsions of

the main microproducts for years 2005-2009 developed by Nexus [4].

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Microproducts

Figure 1: Market breakout of principal microproducts [4].

1.4 Microelectronics based vs Hybrid microproducts

Nowadays the term “microproduct” generally refers to two kinds of microproducts (Table

2): the microproducts based on microelectronic technologies (Micro Opto Electro

Mechanical Systems: MOEMS) and the hybrid microproducts.

Micro mechanical

Micro electronics

HYBRID:

HYBRID:

Semiconductor domain

Mechanical engineering domain

Combination of

Micro mechanical &

Micro electronics

MOEMS:

MOEMS:

Microhandling devices for the assembly of Hybrid Microproducts

MOEMS are mass produced at low cost by using well known microelectronic based

technologies as lithography, etching, doping, lift off technique, surface micromachining.

These techniques, originally developed for processing silicon semiconductor devices,

permit to obtain products made of one or few materials with a 2D aspect. Some

fabrication methods able to realize 3D structure, as LIGA, bulk micromachining and

EFAB, have been proposed but they are not suitable to build up complicated structures

(e.g. microproducts that contain sensors and actuators combined with mechanical parts).

Conversely, the term Hybrid refers to microproducts obtained by the assembly of many

components of different materials such as metals, polymers, plastics, silicon etc. Some of

these components have features with dimensions up to few microns. The different parts

of hybrid microproducts are obtained by precision engineering manufacturing methods

but also by techniques adapted from microelectronic technologies.

In table 3, it is shown an overview of the technologies used for manufacturing

microproducts.

Table 3: Overview of technologies for manufacturing microproducts [1].

Thanks to the assembly phase, this second class of microproducts usually has a high 3D

aspect ratio and the use of different materials and components allows to obtain final

products with characteristics tailored to the task they are designed for. Thus, it gives

hybrid microproducts better performance in comparison with silicon ones in terms of

mechanical properties, wear resistance etc. Furthermore, the assembly phase lets the

choice of the best production method for each part and the possibility to obtain

microdevices with parts made of incompatible technologies. Opposite to silicon-based

microproducts exploiting well-developed microelectronic methods, some micromechanical

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Microproducts

manufacturing technologies are still object of many research efforts for improving their

industrial application. In particular, the assembly phase represents the main obstacle that

does not let the production of hybrid microproducts at low cost. The consequence is that

hybrid microproducts are prevalently developed in research centers and only few of them

are commercially available.

Table 4 shows the main features that make Silicon Based microproducts different from

the Hybrid ones.

Silicon based microproducts

HYBRID microproducts

Mass produced Low production

Low cost High cost

One (silicon) or few materials Various components of different materials 2D/ 2D ½ structure 3D structure

Silicon technologies Precision manufacturing methods + Assembly

Table 4: Comparison among the main features of the Silicon Based microproducts and the Hybrid ones.

1.5 Hybrid microproducts and their applications

Significant hybrid microproducts can be found in different fields, such as the industry and

the automation one, the medical and biomedical field, the watch industry but also the

sport and entertainment sectors.

In the industry and the automation field, micromotors are important examples of hybrid

microproducts. Different kinds of micromotors have been developed in literature (variable

reluctance micromotors [7][8], induction micromotors [9][10], piezo driven linear

micromotor [11]), while many types of permanent magnet micromotors are commercially

available [12][13]. Very compact permanent magnet micromotors are the Penny motor

[14] developed for the market of compact consumer electronics (e.g. miniaturized hard

disk drives, mobile optical scanners etc.) and the ones designed for wristwatches [15].

Brushless DC motors of little dimension and low weight (such as the one shown in Figure

2 [16][17] and the micromotor shown in Figure 3 [12]) have been developed for

automotive [16][17], pumps, ventilators and scanners applications [12]. An

electromagnetic motor is the key component of the teleoperated mobile microrobot [18]

shown in Figure 4. A microstepping motor and a microharmonic drive are the main parts

of a rotary precise positioning device [19] illustrated in Figure 5. The IMT Braunschweig

Institute developed a microelectric linear actuator [20] based on a variable reluctance

micromotor (Figure 6).

Other microproducts of the industry fields are planetary and spur gearheads, micro

harmonicdrives, optical and magnetic encoders, microactuators [11], air microturbines

[21], microdrives [13], microbearings [22].

In the biomedical sector, innovative drug delivery equipment [23][24], robotic systems for

colonoscopy [25][26] implantable centrifugal blood pumps [27] have been developed. The

drug delivery systems, as the one shown in Figure 7, can be implanted in human body to

Microhandling devices for the assembly of Hybrid Microproducts

relieve pain, while the robotic device represented in Figure 8 is an alternative to classical

system for colonoscopy analyses.

Microhybrid products are widespread in the watch industry. Actually, mechanic watches

consider hundreds of parts, most of them with dimension less than one millimeter. This

assembly is carried out by dexterous operators and requires up to 8 weeks [28] for

precious watches!

In the microfluidic field micropumps [29] have been developed by combining silicon based

manufacturing processes and microassembly techniques (such as gluing, joining etc.).

With regard to other fields, a microtouching probe [30][31] able to very accurate

measurement has been developed by TNO University (Figure 9), while at the Karlsruhe

wbk Institute a complete radiocontrolled microcar [32][33] has been designed and

assembled as shown in Figure 10.

• stator assembled in stack of lamination • inserting of the hall sensors in the stator • inserting of the rotor in the cylindrical yoke • stator: sheet of silicon iron

• three hall sensors • rotor: ring magnet

• cylindrical ferro-magnetic yoke (iron)

main assembly tasks components & materials

MMT brushless motors are particularly well suited for high volume, low cost positioning and smooth rotating applications. They are ideal for automotive applications owing to their small flat package and low weight.

1mm

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Microproducts

components & materials

1mm

These rotor motors are especially suited for continuous operations such as pumps, ventilators and scanners.

Figure 3: DC brushless motors [12].

•stator: 3 mini coils, star connected and wrapped around a ferromagnetic core • rotor is a soft iron ring

• polycarbonate frame

• 2 passive wheels (d=2mm) in PVC polymer • driving wheels derived from a rubber tube • electric power supply:18 thin wires (25 µm)

components & materials 1mm

“Pollicino" (Tom Thumb) is a teleoperated mobile microrobot (overall dimensions are 10 mm x 10 mm x 10 mm) incorporating a novel type of electromagnetic micromotor. Two micromotors are used to actuate the wheels of the microrobot that includes only few parts (9 in total) which are fabricated by precision machining and manually assembled. The main innovative component is the micromotor which is based on variable reluctance working principle and moves step by step through a sequence of current pulses. The microrobot is able to move forward, backward and turn left or right. The operator controls the microrobot by a remote joystick and flexible ultraminiature wires.

Microhandling devices for the assembly of Hybrid Microproducts

• inserting of the shafts • keying of the bearings on

the shafts

• assembly of bearings: pick and place of spheres • keying of the motor on the

shaft • bearings

• stainless steel housing • microharmonic drive:

metallic gears • metallic shaft (input

and out put) • micromotor

main assembly tasks components &

materials

1mm

2

1

The “Rotary Bond Tool” (RBT) is a Precise Positioning device with Micro Harmonic Drive Gearboxes® _{developed by Micromotion for orienting in any angular position with high}

accuracy (better than 0.02°) and high speed (90° in ca. 175 ms) minute chips of 0.15 x 0.15 mm or optical fibers. At the heart of the RBT is a Micro Harmonic Drive gearbox (1) driven by means of a stepping motor (2). The hollow shaft is used for an optical sensor which looks through the gear in order to make sure that the chip has been gripped successfully. The output shaft is supported by pre-loaded ball bearings to provide the accuracy and axial stiffness required for the assembly.

Microgear boxes with microharmonic drive

Figure 5: The precise rotary positioning based on a microharmonic drive and a microstepping motor [19].

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Microproducts

• inserting the ruby spheres in the grooves • place the traveler in the exact position relative to

the stator • ceramic stator

• silicon die (with two grooves) • ruby balls

• glass traveler with soft magnetic poles

main assembly tasks components & materials

The actor works according to reluctance principle. The ceramic stator, with six coil systems meandering horizontally round soft magnetic poles, is fixed to a silicon die which has two grooves used as ball tracks. The “v” shaped grooves with the ruby spheres and the flat lower surface of the glass traveler form a ball bearing. The bearing carries the weight of the traveler.

Microhandling devices for the assembly of Hybrid Microproducts

• piston in titanium alloy • casing in titanium alloy

• circular notch hinge in titanium alloy with thickness between 66 and 175 µm • casing in titanium alloy

• globe valves in ruby

• electromagnet in stainless steel

components & materials

1mm

The implantable programmable micropump is a solution to treat chronic diseases such as diabetes with regular micro-injections of medicine. The rotating piston is actuated by an electromagnet. A circular notch hinge is used as piston bearing and guiding system. Two globe valves (one inside the piston and one inside the casing) control fluid displacement during piston rotation.

Chapter 1

Microproducts

Possible valve to be integrated in the actuator block

• mothership

- pneumatic clamping actuators: Plexiglas - miniature air distributor

- inflatable plastic hollow - hemispherical tips • manipulator

-actuation block: valves (see figures a & b) • flexible tail:

- hydraulic and pneumatic tubes - electrical wires

- optical fibers

components & materials 1mm

The endoscope is meant to inspect and intervene in the human colon through which it moves by inchworm locomotion. The micro robotic system comprises four main subsystems: a) a mothership; b) a miniature pneumatic distributor; c) two microarms; d) a Human/Machine Interface (HMI). The mothership consists of two clamping modules connected by an expansion/contraction bellow. Both of them are air actuated. A miniature robotic manipulator is placed at the front of the endoscopic system and is used to orient and position the tools and the camera. The possible actuators to be used for the manipulators are a piezoelectric (A) or an electromagnetic valves (B).

Exploded view of the manipulator

a

b

80

18

Microhandling devices for the assembly of Hybrid Microproducts

• peg in hole and gluing of the stylus in the star • pick and place and gluing

of the sphere on the stylus • ruby sphere (500µm) • steel stylus • teflon pellet • probe housing • screws • flex • silicon chip

main assembly task components &

materials

Assembly sequence

1mm

This nano probe has a high accuracy (in the range of 5 to 10nm) and it can be used to take measurements in machines like those used for the production of DVDs or lenses. The probe consists of a stylus with a ruby sphere. It is fastened to a silicon chip via a three-legged star using epoxy glue. This three legged star is connected to the probe housing via three slender rods. Each slender rod contains four resistors. When the probe tip is displaced, the slender rods will deform elastically, resulting in a change of the resistance value. By measuring the resistance, the deformation of the slender rod is known and is used to calculate the displacement of the probe tip.

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Microproducts

• 95 mechanic components including:

-2 ball bearings inner: diameter 1,4 mm ; outer

diameter 3,95 mm

- brush direct current motor (diameter 6 mm)

• 6 printed circuit boards • 79 electronic parts

components & materials

Rear Axle

Complete System

Front Axle

The mini-maybach 57 scaled 1:87 (H0) was developed in the context of researching on MicroCar Karlsruhe (MiCK). The MiCK is built as micromechatronic system and consists of 95 mechanical components as well as 6 printed circuit boards with 79 electronic parts. A distinctive aspect about MiCK is the high density of mechanic and electronics. The printed circuit boards are arranged 3-dimensionally and this way serves not only as electronic parts but also as supporting elements to strengthen the construction.

Figure 10: The microcar [32][33].

As mentioned in § 1.4, the main issue that limits the diffusion of hybrid microproducts is

their assembly phase. Hence, the complete exploitation of the potential market of these

microproducts will depend on the capability to assembly them at low cost.

In the following Chapter 2, the reasons why the massive and automated assembly of

hybrid microproducts is so difficult and expensive will be described and deeply analyzed.

Microhandling devices for the assembly of Hybrid Microproducts

References

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[15] Gilles, P.A., Delamare, J., Cugat, O., Schanen, J.L., 2000, Design of a permanent magnet planar synchronous micromotor, Proceedings of the IEEE-IAS (Rome), pp. 223-227.

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Microproducts

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