A battery powered lab-on-a-chip biosensing platform with an integrated flexible silver-polyimide microheater for field-deployable isothermal detection of Trypanosoma evansi DNA

Portable nucleic acid amplification platforms commonly use an external thermostat clamped to the reaction cartridge, which introduces interfacial thermal resistance, constrains heater geometry, and reduces the reaction volume maintained within the target temperature range. This work reports a battery-powered lab-on-a-chip biosensing platform that addresses this limitation by directly laminating a flexible silver–polyimide microheater beneath a micro-milled poly(methyl methacrylate) (PMMA) microreactor array and regulating temperature through the resistance of the heater track. The heater functions as the transduction-enabling element because amplification performance depends on maintaining the enzymatic reaction volume within the active temperature window. The eight-chamber PMMA chip was fabricated by benchtop micro-milling, with spindle speed and feed rate optimized using a Taguchi design, reducing mean channel-floor roughness from 0.42 μm to 0.12 μm while maintaining channel width within 2.5% of the design value. The heater was fabricated by cleanroom-free surface-modification ion exchange and doctor-blade deposition of an Ag–poly(vinyl alcohol) composite, producing a temperature coefficient of resistance of 0.0019 °C -1 and resistance change below 1% after 5000 bending cycles. Integrated into a handheld closed-loop device, the cartridge maintained the 35–65 °C isothermal window with a worst-case steady-state error of 0.61 °C. At 40 °C, it reached set point within 3 min, drew less than 0.6 W, and limited spatial variation across eight chambers to ±0.2 °C. Finite-element modelling showed that more than 92% of the 20 μL reaction volume remained within ±1 °C. The chip amplified Trypanosoma evansi DNA with results concordant with micro-PCR and benchtop PCR.