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Automated Syringe Dosing

DeLorme, J.J., Hanson, E.E., Weisshaar, C.L., Wentland, A.L.

BME 400 Department of Biomedical Engineering

University of Wisconsin-Madison December 8, 2004

Advisor

Willis J. Tompkins, Ph.D., Professor Department of Biomedical Engineering

Abstract

Many people, especially elderly individuals, have afflictions along with diabetes, including poor

eyesight, tremors, loss of dexterity, arthritis, and multiple sclerosis. These disabilities make it

difficult for patients to measure and administer medications with a syringe. We have developed

a device that electronically drives the plunger on a standard syringe, reducing the dexterity

normally needed with dosing a syringe. We have constructed a prototype that demonstrates the

feasibility of driving the syringe on a screw-based system with a bimodal stepper motor. In our

next prototype, the device will be handheld and lightweight. We will incorporate a user interface

consisting of a digital display and numerical keypad.

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Table of Contents Page

Abstract 1 Table of Contents 2

Problem Statement 3

National Student Design Competition 3

Background 3

Current Products 5

Contacts 7

Design Constraints 7

Design Approaches 8

Design Evaluation 10

Our Chosen Design 11

Syringe Dosing Device: Operation 12

Prototype 12

Construction of the Prototype 13

Syringe Dosing Device: Advantages 14

Syringe Dosing Device: Disadvantages 15

Syringe Calibration and Preliminary Testing 15

Future Work 16

Ethical Considerations 17

References 18

Appendix A: PDS 20

Appendix B: Expenses 24

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Problem Statement

Our goal is to develop a syringe delivery device that uses standard 1 cc syringes (BD

Ultra-FineTM Needles [1]) and sets the dosage on those syringes within 0.01 cc accuracy. This

device should minimize the dexterity typically needed with dosing a syringe. This device should

be easy to use for elderly patients and those with poor eyesight. Ideally, this machine would be

suited to patients who use syringes on a daily basis, such as those suffering from diabetes.

Patients afflicted with maladies in addition to diabetes, such as neuromuscular disorders and poor

eyesight, would also benefit greatly from this device.

National Student Design Competition

This project is part of the 2004-2005 National Student Design Competition, an

undergraduate competition funded by the Rehabilitation Engineering Research Center on

Accessible Medical Instrumentation [2]. In conjunction with Marquette University, Professor

John Enderle of the University of Connecticut chairs the competition. The competition is open

to students predominantly in biomedical engineering and industrial design. Student teams have a

choice of three projects: a weight scale, a syringe dosing device, or an ergometer, all to assist

patients of diabetes, obesity, paralysis, and neuromuscular disorders. At the University of

Wisconsin – Madison, another team is working on an ergometer [3] while our team is working

on a syringe dosing device.

Background

Diabetes is one of the leading causes of disability in the United States, causing dementia,

low testosterone levels in males, excessive thirst, frequent urination, fatigue, changes in vision,

blindness, stroke, nerve damage, and the need for amputation [4, 5]. Diabetes is typically treated

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with insulin injections, where the amount of insulin is determined by eating habits, exercise, and

ultimately a patient’s blood glucose level. While the changes in vision make it difficult for

patients to see and set the dosage on the syringe, elderly diabetes patients commonly acquire

neuromuscular diseases, albeit unrelated to diabetes. Nevertheless, these diseases make it

difficult for patients to control syringes.

Type 2 diabetes is the most common form of diabetes, affecting 18.2 million people in

the United States alone. This type is found in 90-

95% of the diabetes patients [6]. Those most often

afflicted with this disease are older people. The

Center for Disease Control [6] has predicted that the

number of American diabetes patients will increase

as Baby Boomers grow older and more sedentary.

Type 2 diabetes is characterized by a high blood

glucose level, a high insulin level, and a resistance

to insulin (Figure 1). Contrary to type 1 diabetes,

where insulin does not get produced in proper quantities, type 2 diabetics cannot use their insulin

effectively [5].

A person with diabetes must take daily precautions to maintain optimal health. These

include healthy eating, exercise, and blood glucose testing. Blood glucose testing will tell if the

blood sugar levels are too low (hypoglycemia) or too high (hyperglycemia) [4]. Irregular blood

sugar levels can cause illness, dizziness, nervousness, confusion, fainting, and/or impaired

judgment [4]. Depending on the blood sugar level, insulin may be administered.

Figure 1. Type 2 Diabetes. In this disease, users develop a resistance to insulin, and therefore, blood glucose levels rise [7].

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The injection procedure should be done as recommended by an endocrinologist and is as

follows [8]:

1. Wash hands and area where injecting (usually a fatty subcutaneous tissue area such as the stomach).

2. Wash medicine bottle top with cotton ball and alcohol.

3. Draw air into the syringe equal to the volume of fluid needed.

4. Insert needle into medicine bottle and depress plunger, pushing all air out of the syringe. This action creates a vacuum and allows for easier and smoother filling and delivery.

5. Invert medicine bottle and fill syringe, making sure the needle is not exposed to air.

Air bubbles in the barrel will lead to an incorrect amount of medication.

6. Once the syringe has been filled to the proper amount, keep the bottle and syringe upside down and flick the syringe barrel. This moves air bubbles that may have formed at the top of the syringe.

7. Push the plunger to move the air bubbles into the vial.

8. Check medication dosage.

9. Insert needle into skin at a 90-degree angle and deliver medicine at a slow, steady rate. All medication should be released within 5 seconds.

10. Dispose of needle properly.

It is evident that this is a complicated and involved procedure, requiring a fair amount of

dexterity in controlling the syringe and perspicacity in detecting bubbles. This process should be

simplified for the elderly and individuals with neuromuscular disorders and/or poor vision.

Current Products

Research was done on current devices available to diabetes

patients. Most diabetes patients administer insulin using either an

insulin pump or a syringe. An insulin pump, like the Medtronic Figure 2. Medtronic MiniMed insulin pump. A user programs this device to deliver fast-acting insulin based on the diet and activity of the user. [9]

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MiniMed [9] (Figure 2), provides a constant supply of fast-acting insulin throughout the day [10,

11]. Additionally, the device may be programmed to accommodate eating and exercising habits.

While an insulin pump provides many advantages in terms of convenience, flexibility, and

accuracy, the pump also has some drawbacks. Many patients do not enjoy having a pump

attached to their body. Older patients are often wary of the new, computer-driven technology

and don’t want to feel controlled by a device. There are still many users of syringes. However,

proper syringe operation requires concentration, dexterity, and good eyesight.

Many currently available devices assist in administering the medication, not setting the

dosage. Owen Mumford offers a product called the Autoject 2 [12]. To use this device, the user

fills the syringe to the proper level and places the syringe inside the Autoject 2 (Figure 3). With

the touch of a button, a spring pushes the syringe into the patient and administers the medication.

The device does not assist the patient in

filling the syringe. Consequently, the device

does not increase the accuracy of the user or

compensate for any of the user’s disabilities

to a significant degree.

Another device that assists the user is the Novo Nordisk NovoPen® [13] (Figure 4). The

device uses cartridges of insulin and disposable needles. The

NovoPen® itself is disposable after a month or when the cartridge

is empty, whichever occurs first. The device is used by clicking

the top for each unit of insulin. While patients find this easier to

use than a syringe [14], it still takes a fair amount of dexterity to

click the device, and particularly to not overshoot the desired

Figure 3. Autoject2 syringe device by Owen Mumford [12]. This device assists in injection, but does not assist in setting the dosage on the syringe.

Figure 4. Novo Nordisk NovoPen®. This device uses insulin cartridges. The dosage is set by clicking the device for each unit desired. [13]

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dosage. Furthermore, if the user needs a large dosage, the device would require a lot of clicks,

making it cumbersome and liable to losing count.

Contacts

We have gathered a few human sources to use concerning different aspects of our project.

They are listed below:

1) Missy Midbon [11] – student diabetes patient using a Medtronic MiniMed pump.

2) Kara Yaeger [15] – diabetes educator and nurse.

3) Doug Haist [14] – a 79-year old diabetes and Parkinson’s disease patient.

4) Bern Jordan – a graduate student in the Trace Center familiar with universal design.

5) John Puccinelli – a biomedical engineering graduate student with diabetes.

These contacts will also be useful next semester as we construct a second prototype. The

evolution of our design and first prototype is described below.

Design Constraints

On average, the device will be used twice daily with slow-acting insulin and several more

times with fast-acting insulin to accommodate the eating habits of the user. The device should

function for at least five years under normal use. The device will be designed to accommodate

BD UltraFineTM II 1 cc syringes, which have 80% of the market share [16]. Furthermore, the

device should be easy to use for people with poor eyesight, dexterity, and fine motor control.

Creating a syringe dosing device with universal design in mind is a very important aspect

of this project. The device must be small and portable, yet have features accommodating

presbyopia and individuals with poor neuromuscular control. The device should be easier to use

than the NovoPen® and reduce the amount of interaction a patient has with syringes.

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Should a user, and not an insurance company, pay for the device, the device should be

inexpensive, especially compared to the price of insulin pumps (~$5000). We would like the

design to sell for between $300-$500, with manufacturing costs between $150-$200.

Please refer to Appendix A for our Product Design Specifications, a list of requirements

particular to our final design. See Appendix B for a list of this semester’s expenses.

Design Approaches

We thought of two major ways in which we could design a syringe dosing device. One

such way was to have a device that not only controls the syringe, but also an insulin bottle at the

same time. A device like this would be prohibitively large to be considered portable and is

therefore described in the Tabletop portion of this section. Another way of designing the device

would be to control the syringe alone and let the user continue to control the insulin bottle. This

device would be portable and is therefore described in the Portable portion of this section.

Tabletop

With a tabletop device, a user inserts an

insulin bottle and a syringe into the device

(Figure 5). A user would then type in the

needed dosage of insulin. This input will trigger

the microprocessor to move the syringe towards

the insulin bottle, then to run a motor that pulls

the plunger of the syringe backwards, drawing fluid into the insulin chamber of the syringe.

With that process complete, the syringe will move back to its starting position where it can be

taken out of the device. A user would then remove the syringe and inject the insulin into the

body without assistance.

Figure 5. Tabletop syringe dosing device. The device can hold an insulin bottle and syringe, where a user types in a dosage, the syringe itself moves into the insulin bottle, a motor pulls the plunger of the syringe backwards to draw fluid, and the syringe moves back into its starting position. [17]

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Advantages: Completely eliminates the dexterity needed to dose a syringe and control an

insulin bottle at the same time.

Disadvantages: This design is not portable and provides no assistance in pushing the

plunger while also inserting the needle into the body.

Portable

A portable device would be useful for all users. While users claim that it is difficult to

hold an insulin bottle at the same time as holding the syringe [14], the difficulty truly arises when

a user needs to hold the bottle but also maneuver the plunger of the syringe at the same time.

Our supposition is that a user would have no trouble holding an insulin bottle and a device at the

same time, because only a single button would need to be pressed on the device. Therefore, one

hand would hold the bottle while the other would hold the device, pressing a button to cause the

plunger to draw fluid into the chamber of the syringe.

Below are two methods of controlling the plunger of a syringe in a portable device.

Hydraulics-driven: In a hydraulics-driven design, a piston would

be connected to the plunger of the syringe (Figure 6). This piston would

be controlled by a hydraulic pump, which in turn is regulated by a

control device, e.g. a microcontroller. While this device would provide

plenty of power for controlling the syringe, it may be difficult to fit all of

the components in a portable device without making it prohibitively

expensive.

Figure 6. A hydraulics-driven plunger. The plunger of the syringe is controlled with a piston. [17]

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Motor/screw-driven: In a motor and screw-driven design, a bracket would be attached to

the plunger. This bracket would translate along a screw that rotates according to a motor with or

without gears. While this design doesn’t provide as much power as a hydraulics system, it would

be considerably cheaper to build. It would also be easier to fit this design into a small portable

device. (Please see Figure 8 in Our Chosen Design for a representation of the motor/screw-

driven system).

Design Evaluation

To determine whether to design a tabletop or portable device, we constructed a design

matrix to quantitatively assess the two categories (Table 1). Although this matrix gives equal

weight to all of the criteria, cost and portability are the most important factors. Nevertheless, the

handheld device achieved a lower score than the tabletop design (where a lower score is more

desirable). Qualitatively, a portable device would be more useful, as it provides assistance in any

environment. However, it must be noted that we still suppose that users will not have trouble

holding a device and insulin bottle simultaneously.

Table 1. Design matrix evaluating handheld and tabletop designs, where a lower score is desirable and each criterion is evaluated on a scale of 1-3. Handheld Tabletop Portability 1 3 Cost 1 2 Ease of Use 1 1 Accuracy 1 1 Total 4 7

To determine whether to control a syringe in a handheld device with a hydraulics-driven

system or a motor/screw-driven system, we constructed a design matrix to quantitatively assess

the two designs (Table 2). Although the matrix gives equal weight to all of the criteria, cost and

simplicity are the most important factors. Nevertheless, the motor/screw-driven design achieved

a lower score than the hydraulics-driven system (where a lower score is more desirable).


Qualitatively, a motor/screw-driven device will be much simpler to construct than a hydraulics-

system.

Table 2. Design matrix evaluating hydraulics-driven and motor/screw-driven designs, where a lower score is desirable and each criterion is evaluated on a scale of 1-3. Hydraulics-Driven Motor/Screw-Driven Cost 3 2 Simplicity 2 1 Reliability 2 1 Size 2 1 Strength 1 2 Total 10 7

Our Chosen Design

Based on the criteria we used to evaluate our designs (Tables 1 & 2), we chose to design

a portable device driven with a motor/screw system (Figure 7). A key factor in choosing this

design was that it not only satisfied the requirements of the National Student Design

Competition, but it will be easy to manufacture. Additionally, the mechanical components of the

device are very cheap. The operating steps of this device are provided in the following section.

Figure 7. 3D model of our final design. A syringe can be inserted into the device with the plunger controlled by a motor. The interface includes a numerical keypad for setting the dosage on the syringe. [18]

Figure 8. 3D model of the inner components of our final design. As shown, a screw is attached to a motor. A bracket translates along this screw to move the plunger simultaneously. [18]


Syringe Dosing Device: Operation

Taking the normal procedures to sterilize a syringe, a user will insert the syringe into our

device. The syringe is held in place with collapsible brackets (Figures 7 & 8, shown in red); the

plunger of the syringe will fit into a bracket. The user will then use the numeric keypad to type

in the dosage, pressing Enter when complete. The digital display (top of Figure 7) will instruct

the user to insert the needle into a bottle of insulin. Having done so, the user will press a Fill

button located on the right side of the device (not shown in Figures 7 & 8) where a user’s thumb

will typically be located. This button will cause the motor to run and the bracket to pull on the

plunger, therefore drawing fluid into the chamber of the syringe. The digital display will notify

the user when the process is complete. The display will then instruct the user to insert the needle

into the body. Having done so, the user will press the Inject button located adjacent to the Fill

button. This button will cause the motor to run in the opposite direction as before, therefore

pushing on the plunger and expelling the fluid. Again, the user will be notified when the process

is complete.

Prototype

This semester was devoted to constructing a large-scale model of our design, mastering

its mechanics and feasibility. This prototype was constructed without regard to dimensions and

is therefore much larger than a portable device. As a note: the specific dimensions of our chosen

design (Figure 7) have not been determined. Roughly, the device will measure the length of two

syringes (~10”) and have a diameter that fits in the palm of the hand (~3”). The exact

dimensions of the final prototype cannot be determined until we purchase a smaller motor and

work out the power requirements of the device.


Construction of the Prototype

Figure 9. Picture of our constructed prototype. Annotations are shown for the description below. This model includes a syringe with its plunger controlled by a bracket. This bracket translates along a screw based on the direction the motor is turning. The motor is controlled by a PC with the shown microcontroller. [19]

The long base platform (Figure 9 – 1) and syringe support block (Figure 9 – 2) both

began as large pieces of kiln-dried carving wood. A table saw and band saw were employed to

cut the pieces to the desired dimensions before they were sanded and stained. General purpose

cement was then used to bond the pieces together. Next, the syringe (Figure 9 – 3) was mounted

to the support block using two brackets (Figure 9 – 4) purchased at a local hardware store. With

the syringe affixed, attention was turned toward the screw and its supports.

Two screw supports (Figure 9 – 5) were machined from a block of scrap wood using a

drill press, band saw, and an electric powered sander. Wood was chosen instead of other

materials such as steel or aluminum due to the ease at which it could be machined. The supports

were mounted to the base platform using cement. The threaded rod (Figure 9 – 6) was selected

from an assortment of small diameter threaded rods at a hardware store. One end of the rod was

cut to the desired length and filed flat.

The bracket (Figure 9 – 7) that holds the syringe plunger was machined from a small

block of aluminum. This material was chosen because a high degree of precision was required


for this part and a threaded hole needed to be cut into the piece to accept the threaded rod. An

end mill was used to machine most of the piece geometry. A drill press and a tap were used to

create the threaded hole.

The two-phase step motor and controller circuit (Figure 9 – 8) were purchased as a kit

from online [20]. The kit also included the software required to control the motor from a

personal computer. The motor was mounted to the base platform using a pair of L-shaped

brackets, screws, and bolts (Figure 9 – 9). A small block of wood (Figure 9 – 10) also was

mounted under the motor to provide additional support. The controller circuit was affixed with

contact cement. Following the instructions that came with the kit, the motor was wired to the

controller.

The last piece of the prototype to be constructed was the sleeve (Figure 9- 11) that would

mechanically link the shaft of the motor to the threaded rod. A small section of aluminum rod

was machined with the use of a lathe. A hole with a diameter slightly larger than the diameter of

the motor shaft was drilled halfway into the rod, along the centerline. Another hole, matching

the diameter of the threaded rod, was drilled through the other end of the sleeve to connect the

two holes. A pair of set screws, placed in threaded holes, was used to apply pressure to the

shafts and ensure that a snug fit was obtained.

Overall, the construction of the prototype was relatively straightforward. A fair amount

of machining was required but it was accomplished without much difficulty.

Syringe Dosing Device: Advantages

The motor/screw prototype has a number of advantages over other designs. First of all,

using a two-phase step motor with a step size of 1.8° offers a high degree of accuracy. The step

size is sufficiently small enough to reach the level of accuracy required for the design


competition. The second advantage to this design is that the design itself and the underlying

principles of its operation are very straightforward. While sufficient testing has yet to be done,

the design has shown early indications that it will be quite reliable. A final advantage is that the

final prototype will be very user friendly. All of the complexities of the device will be out of

sight. The user will interface with the device solely through a simple keypad with feedback

provided by a series of LEDs. It is our goal to make the device as user friendly as possible.

Syringe Dosing Device: Disadvantages

While the prototype has many advantages, the design has a few drawbacks as well. One

of the major disadvantages is that the motor and other electrical components will require a

significant power supply. Motors in general require relatively high start-up current. Since the

device is to be portable, the power must come from a battery source. This is a concern due to

obvious spatial limitations. Another disadvantage to the device is that the motor creates some

degree of noise and vibration. Proper motor selection should minimize this problem. Finally, the

cost of the device has the potential to be high. The motor and the microprocessor could drive the

price of the final prototype up, making the device unaffordable to a sufficient group of the

expected users. Again, motor selection will be crucial to ensure that this is not a major issue.

Syringe Calibration and Preliminary Testing

Next semester we will begin writing a program for a microprocessor. This

microprocessor will control the motor and determine how long it needs to run for a given dosage.

It is therefore important to determine if the syringe is approximately linear. Calipers [21] were

obtained to measure the distance the plunger moved from a baseline for every ten units of the

syringe. These measurements were performed along the length of the syringe, for all 100 units,


and repeated three times. A linear

regression was performed showing

approximate linearity, with 0.224

inches between every ten units of

the syringe and an error of +/-

0.00049 inches.

Initial testing was performed on the prototype. Although the motor was not operating

properly when testing was performed, manual rotation of the motor can provide a rough estimate

of the accuracy to which the syringe can be controlled. Since the motor moves in steps of 1.8°,

there are 200 steps/revolution. Through this manual testing it was discovered that approximately

300 steps of the motor correspond to the plunger moving the length of 1.06 units on the syringe.

Regardless of the inaccuracies of manual testing, it should be noted that the prototype is more

accurate than our requirements, because we need to control the syringe to the nearest unit. Since

we can control the motor to the step, the system will be easily within the accuracy of 1 unit.

Future Work

In the 2005 Spring semester, our team will begin the construction of a second prototype.

This prototype will be built with size constraints, limiting the device to portable dimensions.

The construction will not only include the same mechanics as the current prototype, but the

electrical components as well.

Figure 10. Linear regression of the average distance the plunger moves for every ten units on a 1 cc syringe. These measurements were made along the length of the syringe and repeated three times. The average distance between 10 units was 0.224 +/- 0.00049 inches; R2 = 0.99. [22]


Using a microprocessor kit [23], the team will learn how to write a program for a BASIC

Stamp 2 embedded system. This program will be used in conjunction with a numeric keypad

and digital display. Based on the input from the keypad, the microprocessor will run an

algorithm that controls the motor. This algorithm will need to be determined according to the

mechanics of the second prototype.

In the second prototype, the mechanics of the device will be scaled down, including a

shorter screw and smaller brackets. Most importantly, a new motor must be obtained—one that

is considerably smaller than the current motor, but has enough torque to turn the screw. It is very

important that this motor doesn’t vibrate too much when running.

Ethical Considerations

Delivery of the incorrect amount of insulin or other medication could be very dangerous.

Consequently, there must be a way for the patient to easily check that the correct amount of

medication is being administered, and most importantly, that there are no bubbles in the chamber

of the syringe. Even though the chamber of the syringe will be openly exposed, the patient with

poor eyesight will be unable to check for bubbles or an incorrect dosage. If a mechanism was

used to detect these errors, such as a laser checking the passage of light along the length of the

syringe, the device would become prohibitively expensive.


References

[1] BD Diabetes. BD Ultra-FineTM Insulin Syringes. http://www.bddiabetes.com/us/product/thin wall_consumer.asp. 2004. [2] RERC-AMI. 2004-2005 National Student Design Competition. http://www.rerc-ami.org/rerc ami/r2d2/d22-yr2.htm. 2004. [3] Swift, J., Mehta, A., Millin, J., Poper, R. National Design Competition: Ergometer. http://ww w.cae.wisc.edu/~bmedesgn. 2004. [4] Medline plus: National Library of Medicine. Diabetes tutorial. http://www.nlm.nih.gov/med lineplus/tutorials/diabetesintroduction/id029102.html. 2004. [5] Medline plus: National Library of Medicine. Diabetes. http://www.nlm.nih.gov/medlineplus /diabetes.html. 2004. [6] Center for Disease Control. Diabetes: Frequently Asked Questions. http://www.cdc.gov/diab etes/faq/index.htm. 2004. [7] Health. Diabetes Symptom. http://www.diabetes-immune-system.com/. 2004. [8] NIH Clinical Center. Giving a Subcutaneous Injection. http://www.cc.nih.gov/ccc/patient_ed ucation/pepubs/subq.pdf. 2004. [9] Medtronic. MiniMed. http://www.minimed.com/. 2004. [10] Canadian Diabetes Association. Insulin: Things you Should Know. http://www.diabetes.ca/S ection_About/insulin2.asp. 2004. [11] Midbon, Missy. Diabetes patient interview. 9/10/04. [12] Owen Mumford. Autoject 2: Self injection made simpler…http://www.owenmumford.com /autoject2.html. 2004. [13] Novo Nordisk. NovoPen® 3 – An unsurpassed range. http://www.novonordisk.com/diabete s/public/insulinpens/novopen3/default.asp. 2004. [14] Haist, Doug. Diabetes and Parkinson’s disease patient interview. 10/06/04. [15] Yaeger, Kara. Diabetes educator and nurse interview. 09/14/04. [16] BD. Prefilled Syringes Brochure. http://www.bd.com/pharmaceuticals/products/BDPS_bro chure.pdf. 2004. [17] Wentland, A.L. Drawn in Deneba Canvas 9.0.3. 2004.


[18] Lienau, W. of Flite Productions, Madison, WI, USA. Drawn and rendered in 3D Studio Max. 2004. [19] Wentland, A.L. Picture taken with a 5.0 MegaPixel EasyShare DX4530 Kodak Camera. Annotations constructed in Deneba Canvas 9.0.3. 2004. [20] Stepper World. MS-1 Microstepping Motor Control Project: Advanced Microstepping Control. http://www.stepperworld.com/. 2004. [21] Enco. Enco Vernier Calipers. 2004. [22] Wentland, A.L. Linear regression using Matlab Student ed. 6.5. 2004. [23] Parallax, Inc. Parallax #27207 BASIC Stamp Discovery Kit. Oct., 2004.


Appendix A PDS Function:

The device will accept a standard 1 cc syringe of ¼” diameter and automate the process of

measuring and delivering medication. After a syringe is inserted into the device, a user can type

in the number of units that should be drawn into the barrel of the syringe. The user will then

insert the needle into a bottle of medication, such as insulin, and press the “Fill” button. A motor

will drive the syringe’s plunger back via a screw mechanism, drawing the medication into the

barrel. Afterwards, the user will insert the needle into the body and press the “Inject” button.

The motor and screw will drive the plunger in and push the medication into the user. Since the

only manipulation required by the user is pressing numbers on a keypad and inserting the needle

into the body, the amount of dexterity is reduced dramatically.

Client Requirements:

The device should accept 1 cc syringes ¼” in diameter.

The device should dose to the nearest 0.01 cc.

The device should be easy to use for people with poor vision, low dexterity, diminished

motor control, Parkinson’s, and/or other neuromuscular disorders.

Design Requirements:

1. Physical and Operational Characteristics

a. Performance requirements

i. On average, the device will be used twice daily with slow-acting insulin and

several more times with fast-acting insulin to accommodate the eating

habits and varying blood sugar levels of the user.

ii. The device will be modeled to fit BD Ultra-Fine II 1 cc syringes (BD has 75 –

80% market share).

iii. The device should be easy to use for people with poor eyesight and/or

dexterity.

b. Safety


i. Standard syringe safety measures should be taken, including proper sterility

procedures and disposal.

ii. The device will contain batteries, so the batteries should not be left in the

device if they have exceeded their expiration date.

iii. Being electronic, the device should comply with FCC standards.

c. Accuracy and Reliability

i. The device will use 1 cc syringes and dose to the nearest unit, where a unit is

1/100 of a cc.

ii. With the stepper motor in the prototype, the shaft of the motor can move in

steps of 1.8°. In initial testing, 300 steps of the motor corresponded to 1.06 units

being expelled from or drawn in to the plunger. Therefore, the prototype is

accurate to a minimum accuracy of 1/100 of a cc.

iii. This accuracy will be true as long as the syringe dimensions, screw pitch, and

motor increments do not change.

d. Life in Service

i. The device should function for at least five years around five times per day at

five minutes per usage under normal functionality (low-viscosity fluid, such as

insulin, and careful handling).

e. Shelf Life

i. Being electronic, the device should not be left in the sun or in freezing

temperatures. Direct contact of the electrical components with liquids should be

avoided.

ii. The batteries should not be left in the device for more than three years or

beyond their expiration date, whichever comes first.

f. Operating Environment

i. The device should operate and remain accurate at temperatures above freezing

and below 100 °F.

ii. The device should not be affected at different pressures or humidity.

iii. The device will be inoperable if dust, dirt, or water has gotten into the device.

iv. The device can be used by able people of any age above seven.

g. Ergonomics


i. This device seeks to overcome the typical problems that patients with poor

muscular control, tremors, Parkinson’s, and poor eyesight have operating a

syringe.

ii. Anyone who has some control of the hands should be able to use the device,

because the device only requires the pressing of a few buttons with low resistance.

h. Size

i. The device should fit into a single hand.

ii. The device should not exceed the length of two syringes (~10”) or a width of

3”.

iii. It should be completely portable, such as being able to fit into a purse.

i. Weight

i. Ideally, the device should weigh less than a pound.

j. Materials

i. There are no restrictions on the materials, although non-slippery materials are

best.

ii. Materials that are smooth are ideal, so as to ensure comfort of the user.

k. Aesthetics

i. The color of the device should be mild, so as not to attract attention. A colorful

appearance may bring too much attention to a user that prefers discretion.

ii. The device should have a smooth texture, but not too smooth to slip out of the

hands. Rubber grips in key locations would be best.

iii. The device should contour the hand in a natural fashion.

2. Production Characteristics

a. Quantity

i. Potential for thousands of units, depending on the number of patients/companies

that desire the device. For the National Student Design Competition, one

prototype is needed.

b. Target Product Cost

i. Suggested retail price: $300 - $500

ii. Manufacturing costs: ~$150-200

iii. Existing devices that don’t assist in dosing:


- MiniMed pump ~$5000

- Novopen ~$34

- AutoJect ~$44

3. Miscellaneous

a. Standards and Specifications

i. FDA approval required

b. Customer

i. The device should be portable, lightweight, and fit in one hand.

ii. The device should completely eliminate the need to manually set the

dosage on the syringe.

iii. The device should be easy to use, especially for individuals with tremors, poor

muscular control, Parkinson’s, and poor eyesight.

c. Patient-related concerns

i. The device itself will not need to be sterilized, but for each usage, a new syringe

should be used with proper sterilization and swabbing of the skin.

ii. Proper disposal procedures should be taken.

d. Competition

i. Aside from the items listed above, there are no other devices that assist in

dosing syringes to the degree that ours does.


Appendix B

Expenses Budget: $2000

Costs to date:

℘ $13.82 – Supplies at Home Depot (screws, brackets, and glues)

℘ $125 – MS-1 Motor Kit [20] from StepperWorld.com

℘ $178 – Parallax BASIC stamp 2 kit [23]

℘ $39.95 – ZiLog microprocessor kit from DigiKey.com _______________

Total: $356.77

Remaining Budget: $1643.23

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