sensors Article
Portable System for Monitoring the Microclimate in the Footwear-Foot Interface José de Jesús Sandoval-Palomares 1, *, Javier Yáñez-Mendiola 1 , Alfonso Gómez-Espinosa 2 and José Martin López-Vela 1 1 2
*
CIATEC A.C, Omega 201, Industrial Delta, 37545 León, Gto., Mexico;
[email protected] (J.Y.-M.);
[email protected] (J.M.L.-V.) Tecnologico de Monterrey, Campus Querétaro, Epigmenio González #500, Fracc. San Pablo 76130, Querétaro, Qro., Mexico;
[email protected] Correspondence:
[email protected]; Tel.: +52-477-710-0011 (ext. 16100)
Academic Editors: Pak Kwong Chan and Holden King-Ho Li Received: 12 April 2016; Accepted: 29 June 2016; Published: 8 July 2016
Abstract: A new, continuously-monitoring portable device that monitors the diabetic foot has shown to help in reduction of diabetic foot complications. Persons affected by diabetic foot have shown to be particularly sensitive in the plantar surface; this sensitivity coupled with certain ambient conditions may cause dry skin. This dry skin leads to the formation of fissures that may eventually result in a foot ulceration and subsequent hospitalization. This new device monitors the micro-climate temperature and humidity areas between the insole and sole of the footwear. The monitoring system consists of an array of ten sensors that take readings of relative humidity within the range of 100% ˘ 2% and temperature within the range of ´40 ˝ C to 123.8 ˘ 0.3 ˝ C. Continuous data is collected using embedded C software and the recorded data is processed in Matlab. This allows for the display of data; the implementation of the iterative Gauss-Newton algorithm method was used to display an exponential response curve. Therefore, the aim of our system is to obtain feedback data and provide the critical information to various footwear manufacturers. The footwear manufactures will utilize this critical information to design and manufacture diabetic footwear that reduce the risk of ulcers in diabetic feet. Keywords: foot; plantar temperature; plantar humidity; thermal monitoring; humidity monitoring
1. Introduction Diabetic foot complications are a particularly global concern because of their clinical outcome and concurrent economic cost [1]. Therefore, international organizations have made it their goal to prevent and reduce such complications through the use of diabetic footwear. The diabetic foot can be defined as the destruction, of varying degrees, of foot tissue that is associated with neurological abnormalities and peripheral vascular disease in the lower limbs [2]. One of most common diabetic disorders located on the plantar surface of the foot is that of dry skin, which may result in fissure formation and eventually in foot ulceration. Foot ulcers are the most common cause of hospitalization and amputation of the lower limb among those with diabetic foot [3]. Other factors [1] that are known to contribute to foot ulcers include lack of sensation, friction, perspiration, and sweating disorder reduction. That the diabetic foot displays certain complications, such as sweating disorders, which results in dry, cracked skin that bleeds [3], could result in fissure formation and, eventually, in foot ulceration [4,5]. Maintaining the skin of the foot in an optimally-hydrated condition helps to prevent the development of fissuring and ulcer formation [6–8]. Studies [9–12] show the combined effects of increasing or decreasing temperature and relative humidity on the behavior of human skin, show an influence of skin hydration and wetness,
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and some previous studied collected and analyzed the skin changes and the development of superficial ulcer and support surface, considering the microclimate [13,14]. The thermoregulatory sweating abnormality signified early damage in diabetic feet, and assessing skin conditions should help identify neuropathy in diabetic patients with at-risk feet conditions [1]. Since the 1970s there is evidence that the temperature assessment using infrared thermography, contributes to the care of insensitive limbs [15], and that ulcers might by detected by altered temperature of the area; damaged tissue foot areas increases heat on the surface which can be detected and monitored [16]. In this same way, digital thermography experiments using infrared thermal cameras show the association between plantar temperatures and individuals with diabetes [17]. A methodology is presented using infrared thermography and image processing to obtain quantitative temperature differences in the plantar area of the diabetic foot to detect ulceration risks [18]. Studies of microclimate during footwear use are focused in comfort sensations [19] or how low temperature in the ski-boot caused pain sensation, and how comfort is strongly affected by cold feet [20]. An evaluation examined the microclimate in safety footwear and how it may impair specific hygienic parameters, which are critical for wearing comfort and foot health [21], and another study tests the microclimate during footwear use, to obtain the changes in the temperature of the skin of the foot and the temperature and relative humidity of the footwear microclimate for fire fighter footwear [22]. The development of sensor applications as a solution is an important area in healthcare monitoring [23]. It is accepted in literature that it is important to have a quantitative approach to measure temperature and humidity conditions. A monitoring system consisting of a two-dimensional array of fiber optic sensors embedded between two layers of soft, low-loss, and thermally-conductive printed circuit boards (PCB) for a thermal analysis in real-time on the surface of the skin was used in one clinical study [24]. Another development [25] describes an instrumented glove with an array of thermal sensors used to record the human body’s response to thermal conditions in relation to the temperature of the skin and the environment; thus [26,27] present an instrumented in-footwear portable system using independent measuring temperature, humidity, and pressure sensors placed in the insole. TempTouch is a commercial device that reads the surface temperature of the skin using one punctual infrared sensor; allowing the user to monitor his/her temperature. This device was used to conduct a study to identify early signs of vulnerability caused to the diabetic foot. The authors concluded that the temperature monitoring mechanisms were preventive in many cases; as people who underwent traditional foot care control without monitoring temperature were more likely to suffer serious injury or amputation [28]. Nevertheless, there are several studies taking data directly or indirectly about the microclimate in footwear using temperature, relative humidity, and behavior of the skin of the foot, that have not been discussed because they do not completely cover both parameters and how they play a role in diabetic ulcer. In our work, we developed a continuously-monitoring portable electronic device with one array of 10 sensors to obtain microclimate temperature and humidity data of the foot in the insole of the footwear. By implementing the Gauss-Newton method for the calculation of coefficients [29,30], we developed software to display graphics data of the microclimate. The development was created to perform an analysis of the data’s behavior in a graphical 2D approximation of the data to an exponential curve, as well an exponential response curve. We obtained data from system tests with two male subjects. Preliminary results clearly show that temperature and humidity have an exponential behavior that, as time passes, tends to grow, and then remains constant. 2. Materials and Methods 2.1. System Description The acquisition of temperature and humidity data is carried out in the microclimate between the plantar surface of the foot and the sole of the footwear, with a system consisting of three modules.
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firstisisa aportable portable module allows to gather temperature and humidity data10using 10 The first module thatthat allows us tousgather temperature and humidity data using sensors sensors (M1). data is acollected, a second module (M2) M1 with a personal (M1). After theAfter data isthe collected, second module (M2) connects the connects M1 with athe personal computer (PC) computer utilizing a Universal Bus The (USB) interface. third module is the software utilizing a (PC) Universal Serial Bus (USB)Serial interface. third moduleThe is the software interface module interface module that allows fordisplay acquisition and display ofand the data in textFigure and graphics. 1 (GUI) that allows(GUI) for acquisition and of the data in text graphics. 1 depictsFigure a block depicts block diagram of thesystem. implemented system. diagrama of the implemented
Figure 1. Block Block diagram diagram of of system system architecture architecture of of portable portable system system for for monitoring monitoring the the footwear-foot footwear-foot Figure 1. microclimate, microclimate, showing showing the the logical logical configuration configuration of of sensors, sensors, microprocessor, microprocessor, memory, memory, USB USB interface, interface, and and PC. PC.
The consists of of ten The M1 M1 architecture architecture consists ten SHT15 SHT15 sensors sensors (Sensirion, (Sensirion, Stäfa, Stäfa, Switzerland) Switzerland) that that are are capable capable of reading ranges of 100% RH ± 2% for relative humidity and −40 °C to 123.8 ± 0.3 °C for temperature ˝ ˝ of reading ranges of 100% RH ˘ 2% for relative humidity and ´40 C to 123.8 ˘ 0.3 C for temperature in a in aa single single chip. chip. For Forthe theconnection connectionand andcommunication communicationtotothe theprinted printedcircuit circuitboard board(PCB), (PCB),we weused used PIC18F452 microprocessor (Microchip, Chandler, AZ, USA) and AT24C256 memory (Atmel, San a PIC18F452 microprocessor (Microchip, Chandler, AZ, USA) and AT24C256 memory (Atmel, San Jose, Jose, CA, USA). themodule M1 module is autonomous, are ausing a commercial 9V battery as our CA, USA). Since Since the M1 is autonomous, we arewe using commercial 9V battery as our power power source. For future microclimate readings, the sensors were divided into two flexible segments source. For future microclimate readings, the sensors were divided into two flexible segments of of five sensors each connected to the through an interface wire-board connector header 14 five sensors each andand connected to the M1 M1 through an interface wire-board connector header of 14 of pins. pins. Additionally, M1 module includes a display for viewing the temperature and humidity data Additionally, the M1the module includes a display for viewing the temperature and humidity data during during capture. Furthermore, the number of readings and total time to read is controlled by a pair of capture. Furthermore, the number of readings and total time to read is controlled by a pair of buttons buttons thatthe allows user set the time between total of number of readings. The link that allows user the to set thetotime between readingsreadings and totaland number readings. The link between between the M1, M2 and PC is a PIC18F2550 (Microchip, Chandler, AZ, USA) microprocessor that is the M1, M2 and PC is a PIC18F2550 (Microchip, Chandler, AZ, USA) microprocessor that is connected connected to the M1 through an interface wire-board connector header of 14 pins, while the PC is to the M1 through an interface wire-board connector header of 14 pins, while the PC is connected connected using a USB port. using a USB port. 2.2. 2.2. Software Software User’s User’s Interface Interface The that hashas been obtained is stored in a in MySQL database. This The temperature temperatureand andhumidity humiditydata data that been obtained is stored a MySQL database. allows the user to display either stored or current data on the display screen. A Matlab R12 graphical This allows the user to display either stored or current data on the display screen. A Matlab R12 user interface includedistoincluded select and reading data in 2D. Likewise, it Likewise, also allowsitfor comparison graphical userisinterface toplot select and plot reading data in 2D. also allows for of data between different sensors, readings intervals, and calculating basic statistics, such as average comparison of data between different sensors, readings intervals, and calculating basic statistics, such and standard deviation. as average and standard deviation. 2.3. Calculating Curve Behavior For an analysis analysis of ofcurve curvebehavior, behavior,ananalgorithm algorithm was created determine least squares for was created to to determine thethe least squares for the the α and β coefficients an exponential polynomial Incase, this case, the curve not linear, we α and β coefficients of anofexponential polynomial (1). In(1). this as theascurve is not is linear, we opted opted the Gauss-Newton non-lineal iterative method, where y is dependent the dependent variable, for thefor usethe ofuse theof Gauss-Newton non-lineal iterative method, where y is the variable, e is ethe is Euler the Euler number, is theand time theβαcoefficients and β coefficients are the calculated independent number, t is thet time theand α and are the calculated independent variables. variables.
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y “ 1 ´ βe p´α˚tq
(1)
The data was normalized to present a homogeneous level in the range [0, 1] and for the standardization of the data Equation (2), where Mi is the n-th element of the set M, MMax is the maximum value, and MMin is the minimum value of the dataset. Mi “
pMi ´ M Max q pM Min ´ M Max q
(2)
Equation (1) represents a first-order linear system with an input variable x and an output variable y, as follows: . Ty ` y “ x (3) In a Laplace field, the transfer function is expressed as follows: sy psq ` y psq “ x psq
(4)
y psq pTs ` 1q “ x psq
(5)
1 y psq “ x psq Ts ` 1
(6)
where T is the time constant. Now, obtaining the response to the unit step function (x(s) = 1/s), we have: 1 1 . Ts ` 1 s
(7)
T 1 ´ s Ts ` 1
(8)
1 1 ´ s s ` 1{T
(9)
y psq “ y psq “ y psq “ The solution is:
y ptq “ 1 ´ e´t{T
(10)
Which, compared with Equation (1), we have: y ptq “ 1 ´ βe ´ αT
(11)
where β = 1, α = 1/T, then T = 1/α. For our case, β = 1 and α = 1/T define an important independent variable that tells us how fast the answer of the system is. We try to find the time constant T of the exponential response curve of y(t), from 0% to 63.2%, 86.5%, 95%, 98.2%, and 99.3%; that is, the T, 2T, 3T, and 4T time constants of the final value, in correspondence to Figure 2.
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Figure 2. Theoretical exponential response curve. Figure 2. 2. Theoretical Theoretical exponential exponential response response curve. curve. Figure
2.4. Experimental System Test
2.4. Test The sensorsSystem were pre-calibrated by the manufacturer, allowing us to proceed testing the data 2.4. Experimental Experimental System Test collection validating that the system functioned as expected. To verify autonomy, storage, data The The sensors sensors were were pre-calibrated pre-calibrated by by the the manufacturer, manufacturer, allowing allowing us us to to proceed proceed testing testing the the data data transfer, and interface software of the system, tests were performed taking 50, 100, 200, 300, 400, and collection validating that the system functioned as expected. To verify autonomy, storage, data collection validating that the system functioned as expected. To verify autonomy, storage, data transfer, 500 records. transfer, and interface software of thetests system, were performed taking 100, 200, 300, and and interface software of the system, weretests performed taking 50, 100, 200,50, 300, 400, and 500400, records. In our test scenario, we gathered data from two 45-year-old adult male participants who 500 records. In our test scenario, we gathered data from two 45-year-old adult male participants who acknowledged being without diseases or pathologies of their feet and in a general healthy condition. In our testbeing scenario, we diseases gatheredor data from two 45-year-old male participants who acknowledged without pathologies of their feet and adult in a general healthy condition. An insole 1 cm of thickness was made with five circular holes, followed by placing a sensor in each acknowledged withoutwas diseases pathologies of their feet and in aby general healthy condition. An insole 1 cmbeing of thickness madeor with five circular holes, followed placing a sensor in each hole; the holes created an air channel of the microclimate area between the plantar surface-insole and An insole 1 cm created of thickness madeofwith five circular holes, followed placing a sensor in each hole; the holes an airwas channel the microclimate area between thebyplantar surface-insole and the sensor (Figure 3). This allowed the sensor to read the temperature and humidity data without hole; the holes created airallowed channel the of the microclimate area between theand plantar surface-insole and the sensor (Figure 3). an This sensor to read the temperature humidity data without problems. Figure 4 shows the insole with the placement of the sensors. The five sensors were placed the sensor Figure (Figure4 3). Thisthe allowed the sensor to read the temperature and data placed without problems. shows insole with the placement of the sensors. The fivehumidity sensors were in in insoles of both the left and right footwear, with the following division of the foot: two sensors for problems. Figure 4 shows the insole with the placement of the sensors. The five sensors were placed insoles of both the left and right footwear, with the following division of the foot: two sensors for the the forefoot, two sensors for the midfoot, and one sensor for the hindfoot. In a controlled area of 23 ˝°C in insoles two of both the left right footwear, with the following divisionInofathe foot: two sensors forefoot, sensors for and the midfoot, and one sensor for the hindfoot. controlled area of 23for C and 50% relative humidity, insoles were placed inside casual footwear for an acclimatization phase the two sensors forinsoles the midfoot, and one sensor for the hindfoot. controlled area phase of 23 °C andforefoot, 50% relative humidity, were placed inside casual footwear forIn anaacclimatization of of 5 min. The M1 module was turned on and programmed with reading intervals of 1 min and a data and 50% relative humidity, placed inside casual for an acclimatization 5 min. The M1 module wasinsoles turnedwere on and programmed withfootwear reading intervals of 1 min and phase a data collection duration of 60 min. For the first 5 min, data was gathered from the footwear and insole of 5 min. The M1 module onfirst and5programmed with readingfrom intervals of 1 min and ainsole data collection duration of 60 was min.turned For the min, data was gathered the footwear configurations without feet, followed by the remaining 55 min where participants had their feet in collection duration of 60 min. For theby first min, data55 was from the footwear configurations without feet, followed the5remaining mingathered where participants had theirand feetinsole in the the footwear. After 60 min, the system was turned off and the reading cycle was complete. This testing configurations followed byturned the remaining 55 reading min where participants had their feet in footwear. Afterwithout 60 min,feet, the system was off and the cycle was complete. This testing cycle was repeated five times for each individual. After each cycle, the data was downloaded by the footwear. After 60five min, the system was turned off and the reading cycle This testing cycle was repeated times for each individual. After each cycle, the was datacomplete. was downloaded by connecting the M1-M2-PC and using the GUI software. cycle was repeated five times for each individual. After each cycle, the data was downloaded by connecting the M1-M2-PC and using the GUI software. connecting the M1-M2-PC and using the GUI software.
Figure 3. Representative Representative scheme schemeplacing placingsensors sensorsinina acircular circular hole insole, where Figure 3. hole in in thethe insole, andand thethe areaarea where the the air channel of microclimate the microclimate is created, between the plantar surface-insole andsensor, the sensor, to air channel of the is created, between the plantar surface-insole and the to read Figure 3. Representative scheme placing sensors in a circular hole in the insole, and the area where read the temperature and humidity. the temperature and humidity. the air channel of the microclimate is created, between the plantar surface-insole and the sensor, to read the temperature and humidity.
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Figure 4. The five sensors were placed in insoles of both the left and right footwear, with the following Figure 4. The five sensors were placed in insoles of both the left and right footwear, with the following division of the foot: two sensors for the forefoot, two sensors for the midfoot, and one sensor for the division of the foot: two sensors for the forefoot, two sensors for the midfoot, and one sensor for hindfoot. the hindfoot. Figure 4. The five sensors were placed in insoles of both the left and right footwear, with the following
3. Results 3. Results
division of the foot: two sensors for the forefoot, two sensors for the midfoot, and one sensor for the hindfoot.
3.1. Device 3. Results 3.1. Portable Portable Device Figure 55 shows the 3.1. Portable Device Figure shows the modules modules M1 M1 and and M2 M2 with with their their physical physical components. components. The The size size of of the the M1 M1 case case was 5 cm × 7 cm × 3 cm, with a weight of 80 g, including the case, cables, and sensors. The flexible was 5 cm ˆ Figure 7 cm ˆ 3 cm, with a weight of 80 g, including the case, cables, and sensors. The flexible 5 shows the modules M1 and M2 with their physical components. The size of the M1 case cables are 100 cm× long long ×with sensors included; the M1uses usesan ancase, interface wire-board connector header cables are cm sensors included; M1 wire-board connector header of was100 5 cm 7 cm with 3 cm, with a weight of 80the g, including the interface cables, and sensors. The flexible of 20 pins with a power supply with supply voltages of 2.7 V (2.7 V to 5.5 V) and 1.8 V (1.8 V to 100 cmsupply long with sensors included; the M1 an(2.7 interface header 20 pins cables with aare power with supply voltages ofuses 2.7 V V towire-board 5.5 V) andconnector 1.8 V (1.8 V to 3.6 3.6 V). V). The M1of configuration has two segments five individual sensors each, with 20 pins with a has power supply with supply voltages of 2.7 V (2.7 V to 5.5 V) and 1.8 aVmaximum (1.8 V to a 3.6maximum V). The M1 configuration two segments with with five individual sensors each, with resolution The M1 configuration has two segments with five individual sensors each, with a maximum resolution of 100% RH ± 2% for relative humidity and −40 to 123.8 °C ± 0.3 °C for temperature. ˝ ˝ of 100% RH ˘ 2% for relative humidity and ´40 to 123.8 C ˘ 0.3 C for temperature. resolution of 100% RH ± 2% for relative humidity and −40 to 123.8 °C ± 0.3 °C for temperature.
Figure 5. Electronic view of portable system for monitoring the microclimate in the footwear-foot
Figure 5. Electronic view of portable system for monitoring the microclimate in the footwear-foot interface. interface.
Figure 5. Electronic view of portable system for monitoring the microclimate in the footwear-foot The length the data record is 128bytes. bytes. With With 500 records of storage needed for 8 h for of 8 h of The length of theofdata record is 128 500data data records of storage needed interface. continued reading at one minute intervals. Furthermore, The M1 has a display of two lines and both
continued reading at one minute intervals. Furthermore, The M1 has a display of two lines and both a select and enter button to navigate the software menu options. a select enter to navigate menu500 options. Theand length ofbutton thesettings data record isthe 128software bytes. With data records of storage needed for 8 h of The display are as follows: The display settings as follows: continued reading at one are minute intervals. Furthermore, The M1 has a display of two lines and both Date and time settings, reading intervals (in minutes), number of readings to be made and data a select and transfer. enter button to navigate the software menu options. ‚ Date and time settings, reading intervals (in minutes), number of readings to be made and The display settings are asdisplay: follows: Verification of power before starting any new data collection there is a verification of data transfer. the current battery power. If it is below 2.5 V then the display prompts for a battery. ‚ Date and time settings, reading intervals (in minutes), number of readings made andofdata Verification of power display: before starting any new data collection there istoabe verification the transfer. current battery power. If it is below 2.5 V then the display prompts for a battery. Verification of power display: before starting any new data collection there is a verification of the current battery power. If it is below 2.5 V then the display prompts for a battery.
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The amount ofofexisting The amount existingdata datain inmemory. memory. The amount existingdata dataininmemory. memory. ‚ The amount ofof existing ToTo delete or continuereadings readingsoption. option. delete continue ‚ To delete or or continue readings To delete or continue readingsoption. option. Thescreen screendata datadisplays displays the the detected detected temperature temperature and and the The and humidity humidity and thecorresponding corresponding The screen data displays the detected temperature and humidity and the corresponding readings. The screen displays the detected temperature and ×humidity and the corresponding readings. Figuredata depicts theM2 M2 in in portable 2.5 cm 14 14 pinpin readings. Figure 6 6depicts the aa portable 2.5 cm ×× 55 cm cm ×33cm cmcase, case,a awire-board wire-board Figure 6 depicts the6M2 in a portable 2.5 ˆ connection. 5 cm2.5 ˆ 3cm cm 14aM2 pin connector readings. Figure depicts the M2 in acm portable ×case, 5sole cmapurpose ×wire-board 3 cm of case, wire-board 14header pin connector header interface, and a USB V1.0 The the is to send data connector header interface, and a USB V1.0 connection. The sole purpose of the M2 is to send data interface, and a USB V1.0 connection. The sole purpose of the M2 is to send data from M1 to the PC. connector header interface, and a USB V1.0 connection. The sole purpose of the M2 is to send data from PC. from M1M1 to to thethe PC. from M1 to the PC.
Figure 6. Prototype of the portable system for monitoring the microclimate in the interface of foot,
Figure 6. Prototype of the portable system for monitoring the microclimate in the interface of foot, footwear, and insole sensors. system for monitoring the microclimate in the interface of foot, Figure 6. Prototype of with the portable Figure 6. Prototype of the portable system for monitoring the microclimate in the interface of foot, footwear, and insole with sensors. footwear, and insole with sensors. insole with sensors. 3.2.footwear, Portable and Device
3.2.3.2. Portable Device Portable Device system validation tests on two healthy men to demonstrate the feasibility of the We performed 3.2. Portable Device system. Figure 7system shows sensors tests placed intwo a pair of footwear, Figure 8the shows the major We performed validation healthy mento towhile demonstrate thefeasibility feasibility We performed systemthe validation tests on on two healthy men demonstrate of of thethe We performed system validation tests on two healthy men to demonstrate the8feasibility of major the components of the system placed on one of the test subjects. system. Figure 7 shows the sensors placed in a pair of footwear, while Figure shows the system. Figure 7 shows the sensors placed a pair of footwear, while Figure 8 shows the major system. Figure 7 shows the sensors placed in a pair of footwear, while Figure 8 shows the major components ofof the system components the systemplaced placedon onone oneof ofthe the test test subjects. components of the system placed on one of the test subjects.
Figure 7. Array of ten sensors placed on flexible cables in the footwear.
Figure 7. Array of ten sensors placed on flexible cables in the footwear. Figure on flexible flexiblecables cablesininthe thefootwear. footwear. Figure7.7.Array Arrayof often tensensors sensors placed placed on
Figure 8. System placed on one of the test subjects.
Figure 8. System placed on one of the test subjects. Figure 8. System placed on one of the test subjects. Figure 8. System placed on one of the test subjects.
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There were no technical problems that arose during the 300 temperature and humidity data There were nothe technical thattoarose during the 300 temperature and humidity in data readings nor during transferproblems of the data the PC. Participants expressed no discomfort their readings nor during the transfer of the data to the PC. Participants expressed no discomfort in their feet during the experimental validation of the system. feet during the experimental of the system. Temperature monitoring validation of the participants showed an average range of 24.37 ˝ C to 29.27 ˝ C Temperature monitoring of the participants an average range 24.37 to 29.27over °C and ˝ C to 29.41 ˝ C. An exponential and 23.44 growthshowed is observed initially, butof with a °C tendency time 23.44 °C to 29.41 °C. An exponential growth is observed initially, but with a tendency over time for for the curve to move horizontally. Around the 40th minute a slight temperature decrease of 0.2 ˝ C the curve to move horizontally. Around the 40th minute a slight temperature decrease of 0.2 °C is is observed, which can be attributed to additional ventilation produced during foot posture change observed, which can be attributed to additional ventilation produced during foot posture change and/or the effect of temperature measurement uncertainties, Figure 9a shows the corresponding and/or the effect of temperature measurement uncertainties, Figure 9a shows the corresponding experimental readings. In relation to monitoring relative humidity, the results were RH 53.01 to 71.82 experimental readings. In relation to monitoring relative humidity, the results were RH 53.01 to 71.82 and RH 50.13 to 67.75 per participant. Once more, an exponential growth is observed at the beginning, and RH 50.13 to 67.75 per participant. Once more, an exponential growth is observed at the beginning, as as shown in Figure 9b. shown in Figure 9b.
(a)
(b) Figure 9. Graph of experimental measurements: (a) of temperature; and (b) relative humidity. In both Figure 9. Graph of experimental measurements: (a) of temperature; and (b) relative humidity. In both temperature and humidity an exponential growth is observed initially. temperature and humidity an exponential growth is observed initially.
3.3. Software Interface 3.3. Software Interface We implemented a Matalab functions menu that is described below: We implemented a Matalab functions menu that is described below: Getting function: implements an algorithm to verify that the M2 is connected via USB and requests data collection of temperature and from ‚ Getting function: implements an algorithm tohumidity verify that the the M2 M1. is connected via USB and requests data View function: a row-column text data list. collection ofpresents temperature and humidity from the M1. Analysis function: presents the data in 2Ddata graphics, ‚ View function: presents a row-column text list. it is possible to select a particular range reading of interest. ‚ Analysis function: presents the data in 2D graphics, it is possible to select a particular range reading of interest.
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For following data data and anddefined definedranges rangesofofinterest interest(63.2%, (63.2%,86.5%, 86.5%, 95%, 98.2%, and 99.3%), For the the following 95%, 98.2%, and 99.3%), an an exponential response curve was found, and adjustment to the resulting exponential curve was exponential response curve was found, and adjustment to the resulting exponential curve was made made the nonlinear iterative Gauss-Newton method (see Figure by theby nonlinear iterative Gauss-Newton method (see Figure 10). 10).
Figure 10. Software interface of to show the example of adjustment of data of temperature and Figure 10. Software interface of to show the example of adjustment of data of temperature and humidity humidity to the exponential curve. This adjustment was made by the nonlinear iterative Gaussto the exponential curve. This adjustment was made by the nonlinear iterative Gauss-Newton method. Newton method.
4. Discussion and Conclusions 4. Discussion and Conclusions We provided a microclimate monitoring system with sufficient data storage of temperature and We provided a microclimate monitoring system with sufficient data storage of temperature and humidity readings for up to eight continuous hours at one minute intervals of portability and autonomy humidity readings for up to eight continuous hours at one minute intervals of portability and during data collection. The system was designed by placing the sensors in a typical division of the autonomy during data collection. The system was designed by placing the sensors in a typical foot (forefoot, midfoot, and hindfoot); its design allows for their placement in other configurations as division of the foot (forefoot, midfoot, and hindfoot); its design allows for their placement in other well. The results demonstrated the technical feasibility of the construction of a portable system, using configurations as well. The results demonstrated the technical feasibility of the construction of a commercial components at reasonable costs, designed for monitoring temperature and humidity in portable system, using commercial components at reasonable costs, designed for monitoring the footwear-foot interface. In this paper, we conveyed testing results and implemented the iterative temperature and humidity in the footwear-foot interface. In this paper, we conveyed testing results Gauss-Newton method to adjust the curve and show the exponential response curve graph. and implemented the iterative Gauss-Newton method to adjust the curve and show the exponential The results have indicated that the portable system for monitoring microclimates in the response curve graph. foot- footwear interface and in conjunction with the software developed in this work is a useful The results have indicated that the portable system for monitoring microclimates in the foottool for medical applications that may help decrease or prevent the onset of diabetic ulcers and other footwear interface and in conjunction with the software developed in this work is a useful tool for diabetic foot complications. medical applications that may help decrease or prevent the onset of diabetic ulcers and other diabetic We are planning future work to perform studies using several types of footwear, as well as foot complications. working with specific population groups that require specialized footwear, such as factory workers We are planning future work to perform studies using several types of footwear, as well as and patients with diabetes. This work is limited to 60 readings of temperature and humidity, and in working with specific population groups that require specialized footwear, such as factory workers future studies, with different use conditions, longer readings will be considered in order to obtain and patients with diabetes. This work is limited to 60 readings of temperature and humidity, and in a more detailed behavior of the microclimate in the footwear-foot interface. We will also consider that future studies, with different use conditions, longer readings will be considered in order to obtain a the monitored data from this system will help to design footwear in the future, providing information more detailed behavior of the microclimate in the footwear-foot interface. We will also consider that relevant to the best design shape for footwear and the materials from which they should be made, the monitored data from this system will help to design footwear in the future, providing information toward the end of manufacturing footwear with agreeable microclimate properties for the control and relevant to the best design shape for footwear and the materials from which they should be made, prevention of ulcers. toward the end of manufacturing footwear with agreeable microclimate properties for the control and prevention of This ulcers. Acknowledgments: work and publishing costs was supported by CIATEC, A.C. a research institute from CONACYT system, Mexico. Acknowledgments: This work and publishing costs was supported by CIATEC, A.C. a research institute from Author Contributions: All authors considerably contributed to this article. The article was conceived CONACYT system, and structured by Mexico. all the authors who contributed to write, read and approve the final manuscript. José de Jesús Sandoval-Palomares and Javier Yáñez-Mendiola conceived and designed the experiments; Author Contributions: All authors considerably contributed to this article. The article was conceived and Javier Yáñez-Mendiola and Alfonso Gómez-Espinosa performed the experiments and analyzed the data; structured all the authors who contributed to write, read and approve the de final manuscript. José de Jesús José Martin by López-Vela contributed reagents/materials/analysis tools; José Jesús Sandoval-Palomares, Sandoval-Palomares and Javier Yáñez-Mendiola conceived and designed wrote the experiments; Javier Yáñez-Mendiola, José-Martin López-Vela and Alfonso Gómez-Espinosa the paper. Javier YáñezMendiola and Alfonso Gómez-Espinosa performed the experiments and analyzed the data; José Martin LópezConflicts of Interest: The authors declare no conflict of interest. Vela contributed reagents/materials/analysis tools; José de Jesús Sandoval-Palomares, Javier Yáñez-Mendiola, José-Martin López-Vela and Alfonso Gómez-Espinosa wrote the paper.
Conflicts of Interest: The authors declare no conflict of interest.
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