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Most students are usually fascinated when they are first exposed to pH paper. This startling experience will usually keep a chemistry class busy for the entire session period. However, visually impaired students may not be able to see the paper and thus may be unable engage with the learning content independently.

Although it is difficult for visually impaired students to be completely self-reliant in chemistry laboratory experiments and exercises, effort should be made in the design and construction of aiding equipment leading to better autonomy in learning for these individuals. It is necessary and especially useful to develop assistive technologies that are easy to build and can serve to help integrate the visually impaired students into their chemistry classes. Experimental exercises combined with the use of aiding equipment can be excellent tools during chemistry classes to facilitate the teaching–learning process. (1) Such an approach in turn facilitates student engagement and delivers meaningful knowledge in a natural manner.

Visual observations are an essential part of chemistry classes. It is therefore desirable to utilize color-change methods that captivate students and motivate them to conduct chemical experiments enthusiastically, while they learn basic chemistry concepts. However, color-based distinctions can be lost on visually impaired and color-blind students who may be willing but unable to perform such experiments. Moreover, pH-paper-based detecting methods may result in some errors because of the limitations of eye sight resulting in inaccurate readings, even for normal-sighted students. It is in just such cases that every attempt should be made to translate observations into a language understandable to the visually impaired and to provide these students with a chemistry class experience that is comparable to that of their normal-sighted peers. (1,2)

According to American Community Survey (ACS) 2017 data, in the United States, an estimate of around 58 thousand persons, aged 15–20, with a high school diploma or equivalent, reported a visual impairment. (3) The overall proportion of students with visual impairment willing to pursue a scientific career is significantly greater today than it was in the past, (4) and one consequence of this increasing number of university-ready secondary graduates is the now-standard use of assistive technologies in teaching. Colorblindness is a common form of visual impairment affecting as much as 7–10% of the Western population, and patients with this condition experience problems in everyday life when discriminating between or matching fine colors. (5) This means that in a class of 60 students, which is typical in our institution, 4 to 6 students may have color discrimination problems.

1 Figure shows the differences in color perception between color-normal and colorblind individuals for the changing colors of universal pH paper. From this perspective, it is likely that the inability to discriminate pH paper colors could confuse students with colorblindness and thus would make a seemingly easy task more complicated, as very similar colors (as perceived by protanopes and deuteranopes) are on both sides of the pH color spectrum.

Figure 1 Figure 1. Appearance of pH paper colors to individuals with normal color vision (middle), individuals with no functional red cones (i.e., protanope) (top), and individuals with no functional green cones (i.e., deuteranope) (bottom). Simulation of colors seen by protanopes and deuteranopes was performed by color blindness simulation software (open-source software, https://colororacle.org).

Several attempts have been made by different research groups to design and build color-change-based assistive technologies for the visually impaired. These attempts have focused on enabling the visually impaired to understand the perception of color changes when performing a laboratory experiment. One of the very first assistive technologies in this category was the colorimeter, which utilized a light-dependent resistor to identify color changes in acid–base reactions and titrations. (6) When the value of resistance of the light-dependent resistor changes, the balance point changes as well, which corresponds to a given change in dial position via a balance-driven knob attached to embossed dials. However, the colorimeter is not very accurate in detecting yellow colored solutions of different concentrations.

Another color-change-based assistive technology, the submersible audible light sensor, was developed to assist visually impaired students in monitoring color changes, chemical reactions, and precipitate formation in solutions prepared in chemistry laboratories. (7) The submersible light sensor is inserted into the solution, and changes in solution color detected by the sensor produce a distinctive output tone that let users listen and compare a tone pitch to a stored reference pitch. However, the submersible audible light sensor falls short when it comes to detecting faint color changes; as a result, higher concentrations of titrants are needed to effectively activate the sensor when used in titrations. (8)

More recently, an Android-based application was developed that utilizes the built-in camera of a smartphone to detect and quantify color changes during titrations. (9) The application uses the components of the hue–saturation–value (HSV) color space to distinguish color changes. Once a titration end-point is reached, audible sounds and vibrations are generated to notify the user. In order to gain the most reliable results, however, it is recommended that the user stabilize the device and keep the crosshair focused on the solution while performing the titration.

Some researchers have focused on developing assistive technologies that make good use of other senses to compensate for the lack of visual input, that is, allowing users to learn through their olfactory, auditory, and tactile senses. Some compounds such as eugenol and phenolphthalein proved to be completely successful as olfactory indicators for acid–base titrations, which can be of great utility to visually impaired students. (10)

Auditory output (speech and nonspeech sounds) can also be reliable in translating probeware readings into understandable stimuli to the visually impaired. Several assistive technologies, such as talking thermometers and balances, are already available. (1,8)

One of the very first assistive technologies in the auditory output category was the Macrolab project, launched in the early 1980s, which included a series of talking laboratory probes and sensors that were developed for use in science laboratories. (11) However, the high cost of production has limited the practical application of this technology.

Later, computers interfaced with speech output technology were programmed to speak pH readings produced using conventional pH meters. A portable electronic note taker, Braille ‘n Speak, developed in the early 1990s, was successfully interfaced with a computer via RS-232 ports and ASCII output capability. (12) This interface required advanced configuration of RS-232 cable pins, so it remained largely underutilized despite being more cost-effective than Macrolab.

These various attempts have inspired the development of a series of user-friendly interfaces, such as JAWS and LabQuest. (13−15) Job Access with Speech (JAWS) text-to-speech screen reader from Freedom Scientific was interfaced with the Logger Pro scientific data analysis program from Vernier Software and Technology. This interface allowed readings taken by several Vernier probes to be read aloud to visually impaired users. Because of a lack of financial support, this interface was later emulated to work with Window-Eyes, a text-to-speech screen reader distributed by G.W. Micro.

These previous efforts were highly necessary to facilitate the development of the Sci-Voice Talking LabQuest software application. (15,16) LabQuest, a highly reliable portable scientific data collection device, was equipped with text-to-speech screen reader technology, and the full package was made publicly available in late 2011.

The Sci-Voice Talking LabQuest software application allows students to collect data through external, wireless Vernier probeware. The application is commercially available at a moderately affordable price of around $2000 if purchased together with the required software and hardware. This package, however, is good value for the money and offers a lot more than pH and temperature measurements as it involves a comprehensive hands-on science learning experience for visually impaired students who are seeking more advanced education or new laboratory-based skills at later stages of their school life.

Recently, a group of researchers have sought a cheaper alternative to complex and expensive interfaces in measuring temperature. (17) They developed a thermometer equipped with an assistive technology capable of emitting nonspeech sounds and vibration pulses similar to Morse code. Although this accessibility thermometer requires some improvements, it shows considerable potential for use in science laboratories as a low-cost assistive technology for the visually impaired.

Moreover, nonspeech sounds can successfully improve the accessibility for the visually impaired, even in conveying graphic representations, such as the work of a group of researchers in Portugal who converted visual information on infrared spectra into nonspeech sounds using open-source programs and converters. (18) This approach, known as sonified infrared spectra, helped visually impaired users to identify typical functional groups or a set of frequencies related to a particular structural pattern in a molecule.

In 2015, a sophisticated, high-end system was described to prevent inaccuracies in pH values obtained using universal pH paper. (19) This system, however, was expensive, difficult to manufacture, and intended for use in quality control of radiopharmaceuticals. Nonetheless, a device that has a particularly simple structure in technical terms yet permits reliable and understandable pH detection using universal pH paper for the visually impaired can still be designed and manufactured.

On the basis of the previous considerations, this paper reports a simple Arduino-based pH sensor (Design-Bee Sensor) that uses universal pH paper and can be assembled for less than $40, making it ideal for use in laboratory teaching for visually impaired learners. The device is simple to construct and suitable for adoption in school chemistry laboratories because of its miniature size, user-friendliness, and flexible coding.