On a night in January 2018, at least 7 students reported symptoms of being drugged after attending a fraternity party at Stanford link. Although we are only halfway into this academic year, Stanford has already issued seven campus-wide reports about possible aggravated assault/drugging. This is not just a problem within Stanford, drug-facilitated sexual assault (DFSA) is a serious problem among teens and college students nationwide. Our project is deeply motivated by this saddening situation that people around us at Stanford, and the uneasiness caused by the possibility of experiencing such crimes. This project delivers SafeCup, a sensor-embedded smart cup that warns owners if their drink has been tampered with.

What it does

SafeCup is embedded with a simple yet highly sensitive electrical conductivity (EC) sensor which detects concentration of total dissolved solids (TDS). Using an auto-ranging resistance measurement system, designed to measure the conductivity of various liquids, the cup takes several measurements within a certain timeframe and warns the owner by pushing a notification to their phone if it senses a drastic change in the concentration of TDS. This change signifies a change in the content of the drink, which can be caused by the addition of chemicals such as drugs.

How we built it

We used a high surface area electrodes, a set of resistors to build the EC sensor and an Arduino microprocessor to collect the data. The microprocessor then sends the data to a computer, which analyzes the measurements and performs the computation, which then notifies the owner through "pushed", an API that sends push notifications to Android or IOS devices.

Challenges we ran into

The main challenge is getting a stable and accurate EC reading from the home-made sensor. EC is depended on the surface area and the distance between the electrodes, thus we had to designed an electrode where the distance does between the electrod does not vary due to movements. Liquids can have a large range of conductivity, from 0.005 mS/cm to 5000 mS/cm. In order to measure the conductivity at the lower range, we increased the surface area of our electrodes significantly, around 80 cm^2, while typical commercial TDS sensors are less than 0.5 cm^2. In order to measure such a large range of values, we had to design a dynamic auto-ranging system with a range of reference resistors.

Another challenge is that we are unable to make our cup look more beautiful, or normal/party-like... This is mainly because of the size of the Arduino UNO microprocessor, which is hard to disguise under the size of a normal party solo cup. This is why after several failed cup designs, we decided to make the cup simple and transparent, and focus on demonstrating the technology instead of the aesthetics.

Accomplishments that we're proud of

We're most proud of the simplicity of the device. The device is made from commonly found items. This also means the device can be very cheap to manufacture. Typical commercial TDS measuring pen can be found for as low as $5 and this device is even simpler than a typical TDS sensor. We are also proud of the auto-ranging resistance measurement. Our cup is able to automatically calibrate to the new drink being poured in, to adjust to its level of resistance (note that different drinks have different chemical compositions and therefore has different resistance). This allows us to make our cup accommodate a wide range of different drinks. We are also proud of finding a simple solution to notify users - developing an app would have take away too much time that we could otherwise put into furthering the cup's hardware design, given a small team of just two first-time hackers.

What we learned

We learned a lot about Arduino development, circuits, and refreshed our knowledge of Ohm's law.

What's next for SafeCup

The prototype we've delivered for this project is definitely not a finished product that is ready to be used. We have not performed any test on whether liquids from the cup are actually consumable since the liquids had been in touch with non-food-grade metal and may undergo electrochemical transformation due to the applied potential on the liquid. Our next step would be to ensure consumer safety. TDS sensor also might not be sensitive enough alone for liquids with already high amount of TDS. Adding other simple complementary sensors can greatly increase the sensitive of the device. Other simple sensors may include dielectric constant sensor, turbidity sensor, simple UV-Vis light absorption sensor, or even making simple electrochemical mesurements. Other sensors such as water level sensor can even be used to keep track of amount of drink you have had throughout the night. We would also use a smaller footprint microprocessor, which can greatly compact the device. In addition, we would like to incorporate wireless features that would eliminate the need to wire to a computer.

Ethical Implications For "Most Ethically Engaged Hack"

We believe that our project could mean a lot to young people facing the risk of DFSA. These people, statistically, mostly consist of college students and teenagers who surround us all the time, and are especially vulnerable to such type of crimes. We have come a long way to show that the idea of using simple TDS sensor for illegal drugging works. With future improvements in its beauty and safety, we believe it could be a viable product that improves safety of many people around us in colleges and parties.

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