Limits...
Textile Organic Electrochemical Transistors as a Platform for Wearable Biosensors

View Article: PubMed Central - PubMed

ABSTRACT

The development of wearable chemical sensors is receiving a great deal of attention in view of non-invasive and continuous monitoring of physiological parameters in healthcare applications. This paper describes the development of a fully textile, wearable chemical sensor based on an organic electrochemical transistor (OECT) entirely made of conductive polymer (PEDOT:PSS). The active polymer patterns are deposited into the fabric by screen printing processes, thus allowing the device to actually “disappear” into it. We demonstrate the reliability of the proposed textile OECTs as a platform for developing chemical sensors capable to detect in real-time various redox active molecules (adrenaline, dopamine and ascorbic acid), by assessing their performance in two different experimental contexts: i) ideal operation conditions (i.e. totally dipped in an electrolyte solution); ii) real-life operation conditions (i.e. by sequentially adding few drops of electrolyte solution onto only one side of the textile sensor). The OECTs response has also been measured in artificial sweat, assessing how these sensors can be reliably used for the detection of biomarkers in body fluids. Finally, the very low operating potentials (<1 V) and absorbed power (~10−4 W) make the here described textile OECTs very appealing for portable and wearable applications.

No MeSH data available.


Response of a textile OECT in geometry G2.(A) Id vs time curves (Vg = −0.9 V; Vd = −0.3 V) obtained after the addition of different dopamine amounts. The additions are labeled with arrows where the amount of added dopamine is reported. (B) Charge vs. molDopamine plot.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5035988&req=5

f6: Response of a textile OECT in geometry G2.(A) Id vs time curves (Vg = −0.9 V; Vd = −0.3 V) obtained after the addition of different dopamine amounts. The additions are labeled with arrows where the amount of added dopamine is reported. (B) Charge vs. molDopamine plot.

Mentions: Since in wearable applications the sensor cannot be completely dipped in a solution that contains the target compound (for instance when the OECT is integrated in the t-shirt of an athlete), we designed and tested a different device geometry, labeled G2 (Fig. 2C,E) to assess its performance in real-life conditions. The G2 OECT is composed by two parallel rectangular PEDOT:PSS stripes (gate and channel). The electrolyte is confined by a PDMS well in a small area that partly covers both the channel and the gate, in order to minimize the electrolyte volume used in the transistor and to grant an effective and reliable performance in real-life applications. The OECT in the geometry G2 was assessed by adding 10 μL of PBS in the area between the gate electrode and channel to simulate the wetting of fabric due to sweat. The OECT characteristic curves demonstrate (Fig. S8) that the gate potential controls the drain current proving that the little amount of added electrolyte solution is enough to ensure both the electrical contact between the two PEDOT:PSS track and the occurrence of the redox processes required for transistor operation. The sensing ability of OECT in geometry G2 was investigated by adding small amounts of analyte solutions on the operating device. Figure 6 shows the Id vs time graph obtained when dopamine was used as redox active compound. The OECT responds to the additions of redox active molecules with a decrease of Id as previously observed for the ideal conditions (geometry G1). However, after the initial signal variation, Id slowly increases (Fig. 6) until the baseline is again reached: the effect of this behavior is the presence in the I-t curve of several peaks, whose area is proportional to the amount of added analyte. Such a behavior can be explained by supposing that, after the initial current decrease, the analyte is depleted from the electrolyte by the electrochemical reactions which are at the basis of sensor transduction. Such effect cannot be observed in ideal conditions (geometry G1) because in that case the solution close to the transistor surface is continuously renovated. In order to verify this hypothesis, we have calculated the charge that flows at the gate electrode after each dopamine addition. The obtained values are very close to those expected from the dopamine electroxidation process, considering two exchanged electrons for each molecules (see Table S2). Therefore the Id decrease can be explained by an actual change of composition of the electrolyte onto the sensor surface. The peak area linearly depends on the number of analyte moles added on the transistor. The slope of calibration plot is equal to (1.1 ± 0.1) 105 C mol−1 with a R2 of 0.985 and we can thus use this sensor to extract real-time quantitative data on the analyte concentration in the electrolyte.


Textile Organic Electrochemical Transistors as a Platform for Wearable Biosensors
Response of a textile OECT in geometry G2.(A) Id vs time curves (Vg = −0.9 V; Vd = −0.3 V) obtained after the addition of different dopamine amounts. The additions are labeled with arrows where the amount of added dopamine is reported. (B) Charge vs. molDopamine plot.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5035988&req=5

f6: Response of a textile OECT in geometry G2.(A) Id vs time curves (Vg = −0.9 V; Vd = −0.3 V) obtained after the addition of different dopamine amounts. The additions are labeled with arrows where the amount of added dopamine is reported. (B) Charge vs. molDopamine plot.
Mentions: Since in wearable applications the sensor cannot be completely dipped in a solution that contains the target compound (for instance when the OECT is integrated in the t-shirt of an athlete), we designed and tested a different device geometry, labeled G2 (Fig. 2C,E) to assess its performance in real-life conditions. The G2 OECT is composed by two parallel rectangular PEDOT:PSS stripes (gate and channel). The electrolyte is confined by a PDMS well in a small area that partly covers both the channel and the gate, in order to minimize the electrolyte volume used in the transistor and to grant an effective and reliable performance in real-life applications. The OECT in the geometry G2 was assessed by adding 10 μL of PBS in the area between the gate electrode and channel to simulate the wetting of fabric due to sweat. The OECT characteristic curves demonstrate (Fig. S8) that the gate potential controls the drain current proving that the little amount of added electrolyte solution is enough to ensure both the electrical contact between the two PEDOT:PSS track and the occurrence of the redox processes required for transistor operation. The sensing ability of OECT in geometry G2 was investigated by adding small amounts of analyte solutions on the operating device. Figure 6 shows the Id vs time graph obtained when dopamine was used as redox active compound. The OECT responds to the additions of redox active molecules with a decrease of Id as previously observed for the ideal conditions (geometry G1). However, after the initial signal variation, Id slowly increases (Fig. 6) until the baseline is again reached: the effect of this behavior is the presence in the I-t curve of several peaks, whose area is proportional to the amount of added analyte. Such a behavior can be explained by supposing that, after the initial current decrease, the analyte is depleted from the electrolyte by the electrochemical reactions which are at the basis of sensor transduction. Such effect cannot be observed in ideal conditions (geometry G1) because in that case the solution close to the transistor surface is continuously renovated. In order to verify this hypothesis, we have calculated the charge that flows at the gate electrode after each dopamine addition. The obtained values are very close to those expected from the dopamine electroxidation process, considering two exchanged electrons for each molecules (see Table S2). Therefore the Id decrease can be explained by an actual change of composition of the electrolyte onto the sensor surface. The peak area linearly depends on the number of analyte moles added on the transistor. The slope of calibration plot is equal to (1.1 ± 0.1) 105 C mol−1 with a R2 of 0.985 and we can thus use this sensor to extract real-time quantitative data on the analyte concentration in the electrolyte.

View Article: PubMed Central - PubMed

ABSTRACT

The development of wearable chemical sensors is receiving a great deal of attention in view of non-invasive and continuous monitoring of physiological parameters in healthcare applications. This paper describes the development of a fully textile, wearable chemical sensor based on an organic electrochemical transistor (OECT) entirely made of conductive polymer (PEDOT:PSS). The active polymer patterns are deposited into the fabric by screen printing processes, thus allowing the device to actually “disappear” into it. We demonstrate the reliability of the proposed textile OECTs as a platform for developing chemical sensors capable to detect in real-time various redox active molecules (adrenaline, dopamine and ascorbic acid), by assessing their performance in two different experimental contexts: i) ideal operation conditions (i.e. totally dipped in an electrolyte solution); ii) real-life operation conditions (i.e. by sequentially adding few drops of electrolyte solution onto only one side of the textile sensor). The OECTs response has also been measured in artificial sweat, assessing how these sensors can be reliably used for the detection of biomarkers in body fluids. Finally, the very low operating potentials (<1 V) and absorbed power (~10−4 W) make the here described textile OECTs very appealing for portable and wearable applications.

No MeSH data available.