HCDE 451 Final Project Report

By: Bella Mariani, Keya Kadakia, Sami Foell, Anushreya Karir

Sami Foell
6 min readDec 8, 2023


Our project, UPower, is centered around the United Nations Sustainable Development Goal 7: Affordable and Clean Energy. This prototype harnesses the power of piezoelectric crystals, whose material components afford conversion of mechanical stress/energy into electrical energy. UPower’s wearable band incorporates piezoelectric technology that enables the wearer to utilize their movement throughout the day to build up electrical charge within a rechargeable battery. Many low-income, disenfranchised communities lack access to affordable, clean electrical power and light. Thus, UPower empowers users to use piezoelectricity to power an LED light and a charging port.

To accommodate a variety of use cases, the band is modular, composed of two separate items. Each device will include a base component, containing a set of piezoelectric crystals, a rechargeable battery, a USB-A charging port, and a toggleable LED light. The second component consists of two flexible, fabric bands that attach at opposite ends of the base component. Users may wish to create a more traditional wearable such as a watch, necklace, or headband. The second longer band length allows users to wrap the base component around larger items (e.g. backpack, tree, etc.).


01 Cardboard Prototyping

An initial cardboard prototype assisted in uncovering product feasibility and usability. Using this rapid and low-cost technique enabled us to identify opportunity areas in form and function early on. These insights were then noted, and our design parameters (i.e., measurements, functionality, and aesthetic) were adjusted accordingly before jumping into more intensive prototyping.

02 3D Object Prototyping

Creating several higher-fidelity prototypes via 3D printing enabled our team to further understand product feasibility and usability in a more refined manner. This technique had a greater sense of realism and physicality, offering a new perspective on the resources needed to create the product, along with how the product should look, feel, and perform.

03 Soft Goods Prototyping

Our product contained several straps attachable to the base component. Thus, creating a series of fabric bands of varying sizes with securable ends (i.e., must attach to the base) enabled our team to uncover insights into feasibility, desirability, and usability. This method allowed us to gain a better understanding of what material should be used, what attachment method is most optimal, and what lengths provide the most utility.

04 Video Prototyping

Having created a more refined, ‘realistic’ prototype from the previous methods, a video prototype was created to showcase potential use cases, product functionality, and emotional/experiential outcomes. This prototype was shown to participants who answered questions intended to elicit data regarding device usability and desirability.

🔧Implementation + Evaluation

01 Cardboard Prototyping

Our team developed a series of pen sketches with precise measurements. We narrowed in on a minimal, compact design to afford greater production feasibility and smoother user integration. We arrived at two core functions: a battery pack and LED light.

Product Sketches

We then translated these initial sketches to a series of cardboard porotypes assembled via hot glue. This was a quick, low-cost technique that proved useful for setting a baseline of product form and function. Specifically, we gained insights into feasibility building the device’s lid mechanism, LED light interaction, and strap dimensions to afford greater product usability.

Cardboard Prototypes

02 3D Object + Soft-Goods Prototyping

Having gained insights from cardboard prototyping, we created refined digital prototypes that were translated to several 3D printed models. Several fabric straps were sewn (6in and 12 in). A more tangible, precise prototype enabled our team to focus on aspects such as aesthetics, usability, dimensions, and comfort to a greater degree in this medium.

3D Print Iteration Cycle

Each 3D prototype afforded unique insights that allowed for further iterations, until finally arriving at a fourth refined prototype base component and two fabric straps. Specifically, insights regarding device lid mechanism, USB-A port, and strap handle dimensions and structural integrity.

Design Issues From Prints 1–3

The fourth final prototype acted as a culmination of the three previous, solving design pitfalls uncovered from each by adjusting product dimensions, corner radii, and strap length fabric.

Fourth 3D Prototype + Sewn Strap

04 Video Prototyping

Once we arrived a fourth 3D prototype with greater structural integrity, appropriate dimensions, and adequately sewn straps, we created a video-prototype highlighting primary uses cases of UPower, electronic charging, light creation, and the strap modularity.

This video was then shown to 5 participants who were asked to fill out a short Google form post-video to uncover insights regarding device usability and desirability. Example quotes are outlined below:

P1: “It’s a cool device…could be a life saver too…I’ll definitely buy this if it can attach to my leg”

P2: “[It’s] small and has interesting features…love it adds value to everyday action…could be more sleek and modern”

P3: “I found it very useful…the small size could make it convenient and easy to carry…could also have the device be solar powered”

This quotes served as validation for product usability, perceived utility, and overall desirability. Opportunity areas (e.g. leg attachment mechanism) were also uncovered, offering a new basis for future design iterations if this project was to be further pursued later on.


What worked well

Slowly moving our way up in fidelity from pencil sketching, to cardboard, to 3D modeling + sewing enabled us to uncover feasibility and usability pitfalls earlier in our design process. Thus, our later higher-fidelity prototypes were able to be of much higher quality and utility for our users.

Additionally, engaging with participants to elicit design feedback on product utility, aesthetics, and desirability was extremely useful. The substantiative evidence collected after showing 5 participants our video prototype proved to be a fantastic method to see what about our product was appreicated and where experiential pitfalls lay.

What needed improvement

Engaging in user testing earlier on in our design process would have enabled additional prototype iterations to have taken place, thus arriving at a more user-centric final product. Further exploration of the exact electrical capacity of the many types of piezoelectric crystals would be useful to further substantiate product feasibility. Taking into account the small size of the battery pack, confirming the true power threshold would influence what functionality is possible in such a device. Lastly, purchasing the external LED light prior to 3D printing would have potentially less iterations to take place to ensure correct device dimensions.

Next Steps

Given we have received rich user feedback on our fourth 3D prototype, incorporating appropriate adjusts to product functionality and aesthetic would be appropriate. For instance, using a higher-fidelity 3D prototype with greater infill and detailing for a modern, sleek appearance and exploring more strap lengths to afford usage on different surfaces (e.g., human leg). Additional exploration of an even smaller LED component to afford greater space to the piezoelectric system and battery pack should be investigated to provide users with the greatest charge length possible. Thus, conducting research on the energy output of piezoelectric crystals and the cost of small-scale piezoelectric systems in mass production is essential.