Seminar on MEMS in

Medicine

Department of Mechanical Engineering

SDM-CET, Dharwad

2008

Chetan Purushottam Bhat

B.E (Mechanical)

Bio-MEMS

Department of Mechanical Engineering

SDM-CET Dharwad

Synopsis

In the past few decades, microelectromechanical systems (MEMS) have found

themselves being adopted into a wide variety of fields and disciplines. Recently there

has been an increased interest in the use of MEMS in medicine, with opportunities in

areas such as surgical Microsystems (intelligent micro invasive surgery), Therapeutic

Microsystems (health care management system), and Diagnostic Microsystems (biochips

and related instrumentation). The key to many of these applications lies in the

leveraging of features unique to MEMS. BioMEMS represents a promising new direction

in meeting 2lst century health care challenges. Opportunities in miniaturization allow for

new medical procedures to be performed as well as existing procedures to be carried

out less invasively. The ability to apply batch fabrication methods to the manufacture of

BioMEMS might also enable greater accessibility to medical procedures through a lower

overall cost of health care delivery. BioMEMS is expected to revolutionize the way

medicine is practiced and delivered.

Picture of a 350 micron high microneedle, with a base of 250 microns, the flow

channel is 70 microns in its widest direction.

Bio-MEMS

Department of Mechanical Engineering

SDM-CET Dharwad

OBJECTIVES

• To study the different types of sensors used in BioMEMS devices.

• To understand the working principle of BioMEMS devices.

• To study the considerations for product development of BioMEMS device.

• To study the design and fabrication process of BioMEMS device.

• To study the different applications of BioMEMS devices in Medicine.

Bio-MEMS

Department of Mechanical Engineering

SDM-CET Dharwad

INTRODUCTION

WHAT IS BioMEMS?

Microelectromechanical systems (MEMS) are devices that have a characteristic length of

less than 1 mm but more than 1µm. MEMS refer to a collection of micro sensors and

actuators that can sense its environment and have the ability to react to changes in that

environment with the use of a microcircuit control. They include gyroscopes, motors,

pumps in addition to the conventional microelectronics packaging into

microelectromechanical structures for desired sensing and actuating functions, on a

silicon substrate that can be smaller than a grain of sand. The system may also need

micropower supply, microrelay, and microsignal processing units. Microcomponents

make the system faster, more reliable, cheaper, and capable of incorporating more

complex functions. For example, the blood pressure sensors that used to cost $600 and

$50 for every use now costs $2.

Biomedical Microelectromechanical systems (BioMEMS) integrate microscale sensors,

actuators, microfluidics, micro-optics, and structural elements with computation,

communications, and controls for application to medicine for the improvement of

human health. In general, BioMEMS can be defined as ‘‘devices or systems, constructed

using techniques inspired from micro-scale fabrication, that are used for processing,

delivery, manipulation, analysis, or construction of biological and chemical entities’’.

These devices and systems encompass all interfaces of the life sciences and biomedical

disciplines with micro systems. [1]

Bio-MEMS

Department of Mechanical Engineering

SDM-CET Dharwad

ADVANTAGES

Lower cost

Owing to the batch-mode manufacturing techniques borrowed from the integrated

circuit industry, small size die, and consequently large volumes and lower cost have

become possible. [2]

Reliability

Silicon is an almost perfectly elastic material. It also doesn’t erode (wear out). Micro-

machines last much longer than their macro counterparts.

Higher performance

Arrayed sensors can provide simultaneous sensing of multiple modalities (pressure,

temperature, chemical reactions ... etc.), or for increased dynamic range, or for

microscopic scale spatial discrimination of signals [2]

Real-time feedback

MEMS technology provides the real-time feedback surgeons that can improve surgical

outcomes, lower risk, and help control costs by providing the surgeon with real-time

data about instrument force, performance, tissue density, temperature, or chemistry, as

well as provide better and faster methods of tissue/fluid preparation, cutting, and

extraction. [4]

Versatility

The devices can be activated in several different ways. It can be activated by remote

control, giving control to the doctor or the patient. It can be activated on a set time

basis. Some devices are even automatically triggered by sensors built into the device

that detect when the drug needs to be administered. [3]

Minimal Invasive Surgery

Leads to shorter hospital stay and faster recovery times for the patient. The cost of a

minimally invasive procedure is 35% lesser compared to its open surgery counterpart.

While MIS has many advantages to the patient, such as reduced postoperative pain,

shorter hospital stays, quicker recoveries, less scarring, and better cosmetic results. [4]

Tissue Sensing

The ability to distinguish between different types of tissue in the body is of vital

importance to a surgeon.

For example, if a neurosurgeon cuts into a blood vessel while extracting a tumor, severe

brain damage may occur.

Bio-MEMS

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Lab-on-a-chip systems

The advantages of such systems are the microvolumes of biological or biomedical

samples that can be delivered and processed for testing and analysis in an integrated

fashion, therefore dramatically reducing the required human involvement in many steps

of sample handling and processing, and improving data quality and quantitative

capabilities. This format also helps to reduce the overall cost and time of the

measurement and at the same time improves the sensitivity and specificity of the

analysis.

DISADVANTAGES [5]

1) Fabrication facilities are too expensive to be installed only for small volume

production.

(2) Because MEMS fabrication process differs from a device to another, a designer

should know many variations of processes; such high-level designers are very few.

(3) The optimization of a MEMS device requires many repetition of design modification

and trial fabrication. This makes the development phase long and costly.

(4) Those who want to utilize MEMS in various products may not have enough

knowledge of MEMS technology; thus they cannot take the full advantages of the

technology.

Bio-MEMS

Department of Mechanical Engineering

SDM-CET Dharwad

CHOOSING SENSORS FOR MEDICAL APPLICATIONS [6]

There is a need to reduce manual labor and human error as well as to increase reliability

and process automation. The kind of intelligence needed to achieve these objectives can

be provided with sensors. Sensors are used in equipment for surgical procedures,

intensive care units, hospital recuperative care, and home care. With medical

equipment manufacturers and sensor experts working together, state-of-the-art

technologies can be created. Selecting a sensor can be simple if the application and the

parameters that need to be controlled are clearly understood.

Implantable Sensors

Implantable sensors need to be small, lightweight and compatible with body mass as

well as require very little power. Most importantly, they cannot decay over time. The

power requirement is one of the major challenges for working with implantable sensors.

Sensors that can function with no power are perfect, but there are few in the market.

Piezoelectric polymer sensors are small, reliable, require no power and last for a long

time. Such sensors (miniature Piezo film sensor) can be used in pacemakers that

monitor activities of the patient.

There are other ways to power implanted sensors from external sources. When an RF

energy wand is brought close to the location of a specially designed sensor located

inside the body, the sensor wakes up, takes measurements, sends the data back to the

wand by RF link, and goes back to sleep. A sensor with an antenna and a transpondent

will do this job. As an example, an abdominal aortic aneurysm requires a portion of the

weak arteries to be removed and replaced with synthetic tubes. Such a sensor can be

implanted during the procedure to monitor the pressure leaks at the surgical location.

Miniature Piezo film sensor enlarged about 10x Pacemaker X-ray

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Temporary Inserted Sensors

The requirements for sensors that can be inserted through an incision— typically

through a catheter—are less critical than those for implantable. Depending on the

surgical procedure, they need to function for few minutes to a couple of hours.

Ideally, these sensors do not require power to operate, but, if necessary, they can be

powered by external means.

A pair of matched thermistors can be attached to the tip of a catheter, which can be

guided to different locations of the heart to measure blood flow. These thermistors

don’t require external power. The figure shows this type of sensor.

Catheter ablation sensors are another example of sensors temporarily inserted through

incision to effect specific treatments and/or to take measurements during treatment. It

is critical that the force applied by the catheter tip to the target tissue not exceed

predetermined values to avoid any possibility of perforating the target tissue.

Temporary temperature sensor catheter probe

External Sensors Exposed to Fluids

There are several disposable sensors where the sensor stays outside the body, but body

fluids come in contact with it. One example is disposable blood pressure sensors (DPS).

These sensors are used in surgical procedures and ICU to continuously monitor the

blood pressure of the patient. This is the ideal way to measure blood pressure when

intravenous fluids (IV) are administered to the patient. These sensors are replaced once

every 24 hours to maintain hygiene. This sensor module is plugged in to a monitor to log

all information.

A few other sensors come in contact with medication and/or body fluids. One is the

sensor used in the inflation of an angioplasty balloon. In this application, the pressure

Bio-MEMS

Department of Mechanical Engineering

SDM-CET Dharwad

sensor needs to withstand more than 30 bars and monitor the pressure applied to

inflate the balloon. Too much pressure can burst the balloon. Since medication and

body fluids are coming in contact, a silicone gel barrier is used to isolate the rest of the

sensor.

Disposable blood pressure sensor

Devices and External Applications

Medical devices use sensors for external applications in which neither medication nor

body fluids come in contact with the sensors. In most cases, these are non-disposables.

They can either be used in hospital or home care applications. Examples include:

• Load cells for infusion pumps that detect occlusion (tube blockage)

• MEMS-based flow sensors used in spirometers to measure breathing strength of

asthmatic patients

• Extremely small MEMS-based accelerometers to study tremors in Parkinson patient

• MEMS and load cell-based sensors for the conservation of oxygen and also to monitor

oxygen tank levels

• NTC temperature sensors to measure skin/body temperature

Infusion pump load cell to detect occlusion Reusable NTC thermistors used to measure

skin or body temperature

Bio-MEMS

Department of Mechanical Engineering

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Working Principle of BioMEMS device

The applications of BioMEMS can be classified into

• Diagnostic

• Therapeutic

• Surgical

Diagnostic system [7]

The objective of diagnostic system is to discover what is wrong with the people who are

ill. The rapid developments in the field of biochemical sciences, immunology, molecular

biology and semiconductor microfabrication technology has led to the concept of

microdiagnostic kits.

The principle of the microcantilever based diagnostic kit for tuberculosis is similar to

that of the diving board as the increase in the adsorbed mass of antigen 85 complex

causes the bending of the microcantilevers. But in addition to that, the specificity is

provided by the immobilization of antibodies specific for antigen 85 complex on the

upper surface of the microcantilever. When the biomolecular recognition takes place

between them, the adsorbed mass of antigen 85 complex causes the change in stress on

the surface of the microcantilever. The difference in stress at the top and the bottom of

the microcantilever beam causes the elongation of the upper surface of the

microcantilever and the shortening of its lower surface thereby causing the

nanomechanical bending of the microcantilever. The deflection of the cantilever can be

detected by optical, capacitive, interferometric or piezoresistive method.

Microcantilever Based Microdiagnostic Kit For Tuberculosis

Bio-MEMS

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The microcantilever based microdiagnostic kit for tuberculosis would be composed of a

reference and a sensing microcantilever. The mechanical properties of the reference

microcantilever are exactly similar to that of the sensing microcantilever as they have

the same coatings of immobilized biomoleules, same composition and same

dimensions. The use of reference microcantilever is very important as it eliminates non-

specific interactions, thermal drifts and turbulences from injections of liquids. The

device would have two inlets for the patient sample and the normal sample. The patient

and the normal sample would be delivered to the respective sensing and reference

microcantilevers in the device. The unused sample and reagents would be ejected out of

the device through the outlets directly below the microcantilevers. The biochemical

interactions between the antigen 85 complex and the immobilized antibodies would

cause the change in resistance of the piezoresistor integrated at the anchor point of the

sensing microcantilevers with respect to their reference microcantilevers. Based on the

reading of the display reader, the relative resistance change would be recorded. This

would provide information regarding the disease state of the patient sample enabling

effective diagnosis of the disease and early treatment

Therapeutic System

The objective of therapeutic system is to treat an illness or improve a person’s health.

Therapeutic microsystems offer the potential of autonomous care management and

precision delivery of medications. Some key MEMS technologies currently being

incorporated into such systems include micropumps, microvalves, and microneedles.

Biomedical microdevices can benefit many patients with neural disorders. Among the

most successful examples are cochlear implants for the hearing impaired, cardiac

defibrillators, and deep-brain stimulators for the treatment of Parkinson disease and

other movement disorders. Implantable and transdermal drug delivery microsystems

allow patients both accurate and continuous dosing of medication and allow delivery of

drugs directly to their intended sites of action. [8]

Ocular drug delivery device [9] utilizes a passive delivery mechanism to eliminate the

need for control electronics and thus reducing the cost of the system. In order for the

device to be a viable treatment method for chronic diseases, it must be refillable to

allow repeated dosing for many years. Once implanted, the device must precisely and

repeatedly deliver accurate doses and hold enough medication for multiple doses prior

to refilling (~every 2 months). The device should be flexible and conform to the natural

curvature of the eye. An ocular drug delivery device and its placement relative to the

eye are illustrated in figure below.

Bio-MEMS

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Concept of a refillable ocular drug delivery device

The drug delivery tube diameter is set to less than 1 mm. For incisions of this size, the

eye is able to maintain its integrity without the aid of sutures. Support posts are

contained within the tube and the reservoir to prevent the top surfaces of the device

from collapsing when the drug is depleted. A normally-closed check valve prevents

backflow of fluids from the eye into the device. The valve opens above a certain cracking

pressure allowing drug to be dosed from the reservoir to the treatment site.

The intraocular drug delivery device is composed of three individual structural layers of

polymethyldisiloxane (PDMS). The top layer defines the chamber for the refillable drug

reservoir. The middle layer defines the delivery tube and check valve orifice. The bottom

layer forms the base of the device outlining the refillable chamber, delivery tube, suture

tabs, and check valve seat. This layer contains posts that serve as

(1) mechanical supports to prevent the tube or reservoir from collapsing and

(2) the valve seat for the check valve.

The reservoir is secured to the top of the eye, while the shunt is inserted into either the

anterior or posterior chamber (Figure a). A specific dose of medication is dispensed from

the device when the reservoir is manually depressed by the patient’s finger (Figure b).

The reservoir can be refilled with the same or different medication without additional

surgery (Figure c).

Illustration of device operation

Bio-MEMS

Department of Mechanical Engineering

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Surgical system [4]

Surgery is the treatment of diseases or other ailments through manual and instrumental

means. New technologies and procedures have been focusing on minimizing the

invasiveness of surgical procedures. Advances in surgery have led to greatly reducing or

eliminating the invasiveness of surgical procedures.

Current robotic surgery systems have a number of benefits over conventional surgery.

Figure (a) shows an Intuitive Surgical Da Vinci robotic system. In this arrangement, the

surgeon sits comfortably at a computer console instead of having to stand throughout

the entire procedure, which can last up to 5 h. A three-armed robot takes his place over

the patient. One arm holds an endoscope while the other two hold a variety of surgical

instruments. The surgical team can also look at a video monitor to see what the surgeon

is seeing. The surgeon looks into a stereo display and manipulates joystick actuators

located below the display. This simulates the natural hand-eye alignment he is used to

in open surgery (Figure b). Since computers are used to control the robot and are

already in the operating room, they can be used to give the surgeon superhuman-like

abilities. Accuracy is improved by employing tremor cancellation algorithms to filter the

surgeon’s hand movements. This type of system can eliminate or reduce the inherent

jitter in a surgeon’s hands for operations where very fine precise control is needed.

Motion scaling also improves accuracy by translating large, natural movements into

extremely precise micromovements. These advances allow surgeons to perform more

complex procedures such as reconstructive cardiac operations like coronary bypass and

mitral valve repair.

Intuitive Surgical Da Vinci robotic system Intuitive surgical stereo display and joysticks.

Bio-MEMS

Department of Mechanical Engineering

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PRODUCT DEVELOPMENT

When developing a MEMS-based product for the surgical market, it is important to keep

the end in mind. The greatest whiz-bang sensor design and fabrication technology will

not produce a marketable product if the right application is not chosen. The following

points should be taken care of while developing a BioMEMS device.

Evaluate the market [4]

As when building any MEMS product, it is important to evaluate the market for the

device, and in this regard the surgical market is a good one. Targeting a disease for

which there are a large number of surgical procedures performed, such as heart, lung,

cancer, etc., will ensure that the device will receive the required attention from funding

sources, researchers, and surgeons. For example, coronary artery disease has a 120-

billion-dollar economic impact, which has fueled research and development of catheter

devices. The surgical device market has both low-volume/high value products and high-

volume/low-cost devices. The high-volume market is very price sensitive and has low

margins but high volumes, which are attractive to MEMS fabrication facilities.

Interfacing early with the medical community [4]

While it is always important to know your target audience, this is especially important

when developing surgical tools. Partnering with surgeons and doctors early in the design

process yields a deeper understanding of the problems and issues faced in the operating

room. This can shorten the development cycle, as well as result in a tool which better

matches the surgeon’s needs. These surgeons and doctors will be the end users and

clinical champions of the surgical devices and can not only help MEMS engineers to

understand what the real problem to be solved is, but also ensure that the device is

accepted in the medical community. Interfacing early with the medical community will

help to determine if the surgical tool is really needed and if it will be used by surgeons.

Cost [4]

MEMS engineers should take an honest look to determine if MEMS really is the best

choice to solve the problem, or if competing technologies will perform better. Not only

must the surgical tool compete with other devices technically, but it must also compete

on a cost basis. This has become more important now that medical providers are under

great pressure to reduce costs. Before developing a product it is important to do the

math. The device must make a significant impact on a medical procedure to justify any

additional cost. In order to do this, MEMS engineers need to focus on disruptive

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technologies which will reduce the skill needed to perform complex procedures and

allow them to be performed in more convenient and lower cost settings.

Biocompatibility [10]

MEMS devices which come into contact with the body must be biocompatible.

Biocompatibility is defined by The Williams Dictionary of Biomaterials as “the ability of a

material to perform with an appropriate host response in a specific application”. The

biocompatibility requirements vary considerably depending on the device function and

design; The ISO 10 993 standards outline minimum tests of material characterization,

toxicity, and biodegradation that may be augmented depending on actual device usage.

Biocompatibility is a surface-mediated property, and the biocompatibility of a device

depends only on those materials in contact with tissue. The biocompatibility of silicon

and other MEMS materials has become much more important with the advent of

implantable MEMS devices that interact directly with the body. Biocompatibility is a

surface-mediated property, and the biocompatibility of a device depends only on those

materials in contact with tissue. The biocompatibility of silicon and other MEMS

materials has become much more important with the advent of implantable MEMS

devices that interact directly with the body.

Packaging [5]

Packaged MEMS devices must be able to survive the sterilization procedures used in the

surgical environment. They must withstand exposure to high temperatures and

moisture in autoclaves and steam sterilizers. Alternative sterilization methods include

ethylene oxide and irradiation. Ethylene oxide is a harsh organic solvent and packages

must be made of a compatible material. For each application area the packaging

challenge is different. In addition, packaging costs are usually considerably more

expensive than the MEMS device itself.

Regulatory controls [4]

Medical products, of which surgical tools are a subset, are subject to many regulatory

controls. The Food and Drug Administration (FDA) and European Community (EC)

determine whether a product is fit for sale in the United States and Europe,

respectively. Any MEMS devices which have biomedical applications (BioMEMS) such as

DNA chips, pumps, blood glucose detectors, catheters, cochlear implants, and blood

analyzers fall under their jurisdiction. Historically BioMEMS have had design cycles

between 5 and 15 years long. Of this time, one to two years have been used for getting

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the necessary agency approvals. Agencies require that all claims be verified for

effectiveness and that the product has proven to be reliable in many sets of clinical trials

before they allow a product on the open market. The approval process for disruptive

technology can be substantially longer. These agencies also have current good

manufacturing practices (cGMP) on how medical devices must be fabricated. These

procedures establish a set of standards which aim to ensure that quality products are

produced.

Lengthy sets of clinical trials can be avoided if MEMS sensors are applied to existing

surgical tools and do not claim to alter the performance. Retrofitting existing surgical

tools is the preferred method of entry for MEMS companies because it is the fastest

path to market. Retrofitted tools have already been accepted by surgeons who are

familiar with their applications and use. Another advantage for MEMS companies is that

they themselves do not have to pay for costly clinical trials, which can be avoided by

modifying existing tools. If clinical trial cannot be avoided, MEMS companies can partner

with device manufacturers to reduce costs and use their expertise in trials.

Bio-MEMS

Department of Mechanical Engineering

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Design and Fabrication of BioMEMS devices

The design process of BioMEMS device is similar to the IC design.

The parameters considered for BioMEMS design are as below

Conception of new device

CAD design and simulation

Fabrication

Concept of new device [11]

Once a study is carried out as to the requirements of the surgeon or doctor a BioMEMS

engineer has to decide on the size, material, precision and accuracy, sensing element,

actuation element, type of link etc. In case of BioMEMS the selection of the material is

of utmost importance. Depending on the application of device either external or

internal, suitable material has to be selected. The material must not be degradable or

corrodible when it comes in contact with body fluids.

CAD Design and Simulation [11]

A Particular challenge for MEMS is the establishment of self-contained, completer and

integrated modeling and simulation suite appropriate to computational analysis

requirements. The Finite Element Analysis software has proven useful for modeling a

variety of parameters like displacement stress, electric field, magnetic field,

temperature and fluid velocity. Using the MEMS-specific tools complete structural and

operational analysis can be done.

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The software’s available for MEMS design are MEMCAD and CAEMEMS

Fabrication Techniques

Bulk Micromachining

Bulk micromachining is a fabrication technique which builds mechanical elements by

starting with a silicon wafer, and then etching away unwanted parts, and being left with

useful mechanical devices. The methods commonly used to remove excess material are

wet and dry etching, allowing varying degree of control on the profile of the final

structure.

Wet etching

Wet etching is obtained by immersing the material in a chemical bath that

dissolves the surfaces not covered by a protective layer. The main advantages

of the technique are that it can be quick, uniform, very selective and cheap.

Dry Etching

Dry etching is a series of methods where the solid substrate surface is etched by gaseous

species. The etching can be conducted physically by ion bombardment (ion etching or

sputtering and ion-beam milling), chemically through a chemical reaction occurring at the solid

surface (plasma etching or radical etching), or by mechanisms combining both physical and

chemical effects (reactive ion etching or RIE)

Surface Micromachining

Unlike bulk micromachining in which microstructures are formed by etching

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into the bulk substrate, surface micromachining builds up structures by adding materials, layer

by layer, on the surface of the substrate. The thin film layers are typically 15 µm thick, some

acting as structural layer and others as sacrificial layer. Dry etching is usually used to define the

shape of the structure layers, and a final wet etching step releases them from the substrate by

removing the supporting sacrificial layer.

A typical surface micromachining process sequence to build a micro bridge is shown in Figure,

Phosphosilicate glass (PSG) is first deposited by LPCVD to form the sacrificial layer. After the

PSG layer has been patterned, a structural layer of low-stress polysilicon is added. Then the

polysilicon thin-film is patterned with another mask in CF4 + O2 plasma. Finally, the PSG

sacrificial layer is etched away by an HF solution and the polysilicon bridge is released.

Basic process sequence of surface micromachining

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A Surface Micromachined component

LIGA

LIGA is a technology which creates small, but relatively high aspect ratio devices using x-

ray lithography. The process typically starts with a sheet of PMMA. The PMMA is

covered with a photomask, and then exposed to high energy x-rays. The mask allows

parts of the PMMA to be exposed to the x-rays, while protecting other parts. The

PMMA is then placed in a suitable etchant to remove the exposed areas, resulting in

extremely precise, microscopic mechanical elements.

LIGA is a relatively inexpensive fabrication technology, and suitable for applications

requiring higher aspect ratio devices than what is achievable in Surface Micromachining.

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A graphic description of LIGA process

A product of LIGA Micromachining

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Applications

Owing to the batch-mode manufacturing techniques borrowed from the integrated circuit industry, small size die,

and consequently large volumes and lower cost have become possible. These advantages have allowed

MEMS devices to displace old products while providing equivalent (or added) functionality. The various

applications of BioMEMS devices are shown in the figure below.

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Cardiovascular Monitoring and Diagnosis

Disposable Blood Pressure Sensor – Very low-cost miniature silicon MEMS pressure

sensor used in line with IV unit

Electronic Stethoscope – Piezoelectric film used as a contact microphone to receive

heartbeat and breathing sounds

Electronic Stethoscope – Piezoelectric film used as a contact microphone to receive

heartbeat and breathing sounds

Cardiovascular Treatment

Ablation catheter – Force transducer measures precise location of catheter tip during

heart ablation to correct arrhythmia

Angioplasty Balloon Inflating Pump – Silicon MEMS pressure sensor measures inflation

of angioplasty balloon

Oxygen Conserver – Piezoelectric film or Silicon MEMS pressure sensor detects

inhalation and opens oxygen flow valve

Oxygen Tanks – Microfused™ load cells measure remaining oxygen level in tank

Patient Monitoring and Diagnosis

Bone Density – Piezoelectric film used as an ultrasound transducer to measure bone

density

Body Fat Scale – Electrodes used to determine body fat through electrical impedance

Body Weight – Microfused™ load cell used on a scale for patient weighing

Hospital Bed Vital Signs – Piezoelectric film used to measure breathing patterns and

heart rate; Microfused™ load cells to monitor patient weight and

departure from bed

Patient Treatment

Ambulatory Infusion Pumps – Si MEMS pressure sensors or Microfused™ load cells used

to detect presence and/or rate of flow

Bubble and Level Detection – Ultrasonic sensors detect bubbles or medication levels

during infusion

Hospital Gas Monitoring – Si MEMS pressure sensors detect gas flow for hospital

medical gas systems

Infusion Pump – Piezoceramic diaphragm used to drive fluid at very slow rates

Kidney Dialysis – Microfused™ strain gage pressure sensor used to measure liquid flow

pressure

Surgical / Delivery

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Baby Delivery System – Silicon MEMS pressure sensor used to monitor pressure on

vacuumassist baby delivery system

Body Heat Exchange – Si MEMS very low pressure sensor measures partial vacuum used

to expand the blood vessels for quick heat exchange

Disposable Digital Display – Low-cost Silicon MEMS pressure sensor with display

measures knee pressure during surgery

Kidney Transportation – Disposable blood

pressure sensors enable flow through organs during

transport to extend organ life.

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CONCLUSION

• The BioMEMS devices promises to change the practices in medical field.

• The implantable sensors are the most useful

• LIGA Micromachining is the best process for Fabrication

• The MEMS CAD needs improvements

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REFERENCES

1. BioMEMS by Nabiollah Abolfathi

2. Nadim Dale Gee, Kurt E. Petersen, and Gregory T.A.Kovacs, Stanford University,

Center for Integrated Systems “Medical Applications of MEMS”

3. Aaron Alexander, Lucas Rogers, Dan Sheehan, Brent Willson, Northwestern

University, “Microelectromechanical Drug Delivery Systems”

4. KEITH J. REBELLO, MEMBER, IEEE, Invited Paper, “Applications of MEMS in Surgery”

5. Robert L. Bratter, Cronos Inteyrated Microsystems, “Commercial Success in the

MEMS Marketplace”

6. Bala Kashi, Measurement Specialties, “Choosing Sensors for Medical Applications”

7. Sandeep Kumar, Ram P Bajpai, Lalit M Bharadwaj, 2004 IEEE, “Diagnosis Of

Tuberculosis Based On BioMEMS”

8. Dennis L. Polla University of Minnesota, 2001 INTERNATIONAL SYMPOSIUM ON

MICROMECHATRONICS AND HUMAN SCIENCE, IEEE, “BioMEMS Applications in

Medicine”

9. Ronalee Lo, Kenrick Kuwahara, Po-Ying Li, Rajat Agrawal, Mark.S.Humayun, Ellis

Meng, University of Southern California “A Passive Refillable Intraocular MEMS Drug

Delivery Device”