Design that Matters, a Massachusetts non-profit corporation, is dedicated to improving the quality of life in underserved communities. We do this by fostering the development of products and services that meet immediate community needs in areas such as clean water, health care, renewable energy and education. We also do this by developing curriculum materials that engage university engineering, science, policy and business in the design process, thereby strengthening their commitment to serve these communities throughout their careers. Since its launch at MIT in 2000, DtM has worked with over 300 engineering and business students to develop dozens of prototypes that promise to improve thousands of lives.

To learn more about our work in communities and universities around the world, see the DtM homepage.

DtM Design Challenge Portfolios

These are curriculum materials that we provide to faculty in industrialized and developing countries to use in their courses and research. We solicit our network of collaborators for well-defined problems in areas such areas as clean water, health care and renewable energy. We package these problems into design challenge portfolios.

To learn more, see the DtM design challenge portfolio library.

Amy Smith's Screenless Hammermill

Here is an overview of Amy Smith's screenless hammermill design. Amy has built and field-tested this device in Senegal. We're bringing data and technical specs for our NGO collaborators in Mali and Benin.

Here is a conventional hammermill, which features a metal mesh or screen to separate the flour from the rubbish [Photo courtesy Amy Smith].

Here is a picture of Amy's screenless hammermill prototype, which she built in Senegal.

A new type of hammermill was designed to operate without a screen. To further reduce milling fees, the mill was designed to minimize the manufacturing and operating costs. [...]

Further improvements to the mill include a single hammer blade which is directly mounted to the motor shaft and a grits discharge which allows continuous operation of the mill. These improvements allow the mill to be produced at about a quarter of the cost of conventional hammermills. In addition, the energy consumption to operate the mill is decreased by about seventy percent and a superior product is produced." -- Amy Smith

Adaptive Wind Turbines

During our meetings with Ibrahim Togola and Tom Burrel at the Mali Folkecenter, we discussed the idea of an adaptive, small-scale (order 1-100 kW) wind turbine and generator set. Over the last year, Design that Matters has been conducting research into the feasability of designing a small wind turbine that is robust and protects itself from damage in high winds. Large-scale turbines can rotate the turbine blades so as to shed the load in high winds. With small turbines, the blades just tend to snap off or the generator gets wrecked from spinning too fast.

Here is a simple turbine design, from a water pump in Segou.

Ibrahim and Tom agree that a low-cost adaptive turbine would be useful--it remains to be seen whether it's feasible. The adaptive component for small turbines could be as simple as flexible vanes, or vanes that can rotate in their sockets, up to something with motorized turbine blade sockets and a control system.

Charge Controller for Kinkajou

Photovoltaic (solar) cells and human-power generation represent two possible means of recharging batteries in off-grid rural communities. What we need a simple, low-cost robust circuit for connecting both DC appliances like the Kinkajou microfilm projector and their batteries to various power sources.

What we're looking for is a circuit for the Kinkajou that we can connect to something like a pedal generator or solar panel and:

• run the Kinkajou directly from the renewable power source


• run the Kinkajou while charging the batteries with the extra juice


• charge the batteries directly while Kinkajou LED is switched off

The charge controller has to be smart enough not to overcharge the batteries, and it can't overdrain the batteries when the generator is off. In addition to the Kinkajou projector, such a circtuit could be applied to any battery-operated device intended for rural communities, like a radio or Light Up the World's solid-state home lighting systems.

Battery Charger for Village Flashlights

In Kemon, like many rural communities in developing countries, is not connected to the national power grid. Batteries represent the only source of electricity for most community members. People use disposable AA and C batteries to power their flashlights and radios. Compared to prices in the States, batteries are dirt cheap: 100 CFA (roughly US$0.20) for a AA battery, and 150 CFA (US$0.30) for a C battery. The quality isn't great. Two C batteries in a flashlight will last about two weeks, but this is partly a function of how amazingly dark it gets at night in the village. People can still make use of a pretty dim flashlight.

There are about 2,000 flashlights in operation in Kemon alone. As a result, battery disposal is a major environmental problem. This concrete-lined disposal pit, a project initiated by PCV Elizabeth Eckel and MVV, currently holds 8,000 discarded batteries collected by local schoolkids over one year. The pit has room for another 8,000--or another year's worth of discarded batteries.

Some batteries are taken apart for recycling--the contents used to make paint for school chalkboards. The rest follow the village garbage to one of the designated village dumps.

Even with the dump, you can still find little collections of garbage pretty much everywhere around the village--and these collections often include batteries. Battery chemicals leach into the soil and the ground water. Worse, little kids will pick up discarded batteries to play with, putting them in their mouths or pulling them apart to see what's inside.

MVV has asked DtM to investigate methods for charging rechargable AA and C batteries that work without any connection to the grid. The resulting device can be powered by human effort, solar energy, whatever. Regardless of how it works, it has to be robust and/or cheap. For comparison, in Kemon an imported Chinese flashlight made out of stamped tin with a low-wattage incandescent bulb costs about a dollar. Use that price to scale against commercially available battery chargers in the US.

Condom Vending Machine

Back at AJA in Mali, the director Souleymane Sarr asked DtM to look into ways to improve their design for a condom vending machine. AIDS, or SIDA in French, is a huge and growing problem across Africa. In conservative Muslim societies like Mali, young men are often put off from buying condoms due to the attached social stigma of premarital sex. The coin-operated, purely mechanical AJA machine is designed to provide an easy, anonymous alternative to buying condoms at the pharmacy or local boutique.

Several international and local organizations are involved in public education about the use of condoms. These include distributing stickers with pro-condom messages, organizing rallies and parades for young people, and setting up roadside stands for condom distribution. There are also lots of billboards advertising condoms and safe sex in general--this particular sign, from downtown Cotonou, Benin, is aimed at truck drivers, a population particularly at risk for becoming infected with HIV/AIDS, and often responsible for spreading the disease to the rural communities they pass through.

Issues with the current design of the AJA condom vending machine relate to reliability and noise.

The 100 CFA coin (equivalent to US$0.20) necessary to operate the machine is about the same diameter as an American quarter, but thicker and heavier (exact dimensions will be posted when we get back to Cambridge). The vending machine must be able to reliably distinguish between denominations, and to avoid it getting abused by an irate customer, it should reliably eject incorrect coins. The machine should have a window or some other means of indicating the supply of condoms remaining. The ability to make change is currently considered outside the scope of the design.

In terms of dispensing condoms, the machine's current hopper and slide has a habit of jamming. It may also be possible for a particularly frenzied customer to shake condoms lose without paying anything, which sort of defeats the purpose of a vending machine.

In terms of noise, the current plunger-driven, spring-controlled vending mechanism makes a sound like a rusty guillotine--one that doesn't exactly convey a sense of discreetness and anonymity.

Video of the AJA condom vending machine in action will be posted when we get back to Cambridge.

Design Challenges at the Centre Songhai

Centre Songhai was a gold mine for potential DtM design challenges. They also have the facilities and trained staff necessary to build and test many existing DtM prototypes. Finally, they have an extensive network of collaborators both with in West Africa and abroad, with whom they can exchange ideas and disseminate successful new designs.

We collected a trunk-load of preliminary data on a number of potential DtM design challenges, including this prototype palm nut shelling machine, based on a Nigerian design and currently in development at the Centre.

Fr. Nzamujo also asked DtM to look into continuing the development of a low-cost reduction gear for their various agricultural-processing equipment. Shown below is an expensive reduction gearbox imported from the US, alongside a less expensive gear set built at Songhai, made from a gearbox salvaged from a Peugeot 504.

According to Nzamujo and the staff at Centre Songhai, he toughest problems--"casse-têtes" or literally head-breakers--also involve agricultural production. Songhai is committed to developing methods for micro-production of agricultural goods, in other words, tools for adding value to the raw produce of rural agriculture. These include shelling machines, peeling machines, juice-making machines, seed presses, cotton separators, coffee roasting machines, etc. The idea is to allow rural communities to capture more of the value of the goods they produce, and also to reduce their vulnerability to fluxuations in the international prices for raw goods.

For example, in terms of a specific project, both Centre Songhai and MVV in Kemon are looking for machines to shell both sunflower seeds and sesame seeds. In both cases, there is currently no alternative to the current system of small-scale local production in the village which involves laboriously shelling both kinds of seeds by hand. Sunflower oil in particular is a nutritious and valuable commodity. Presses for the shelled seeds exist; a shelling machine would be an invaluable complement.

Another specific project is a machine to peel manioc (cassava), a starchy tuber grown throughout the tropics as a food staple. Maniocs come in a bewildering variety of shapes and sizes; as with sunflower seeds, the only means of peeling the stuff at the village level is by hand.

We have tons of additional material from our visit to the Centre, which we will process and format as formal DtM design challenges when we get back to Boston.